VII. VEGETABLE OILS AND FATS, AND NUTS
VEGETABLE OILS AND FATS.
The production of a substance known as fat or oil, composed of oxygen, hydrogen, and carbon in the form of a fatty acid and combined with glycerine, is a function of almost every plant. The fat acids are usually in combination with glycerine, which plays the part of a base and in so far as its proportion by weight is concerned is much less important than the fatty acid itself. In round numbers it may be said that nine-tenths of all glycerids or fats are composed of a fatty acid and one-tenth of glycerine. When at ordinary temperature this combination is in a liquid form it is called an oil, and when at ordinary temperature it is in a solid or semi-solid condition it is known as a fat. The term “ordinary temperature” means in this connection that of an ordinary living room and not the extremes of outside temperature. In general terms it may be said that the temperatures referred to are included between the minimum of 50 degrees and the maximum of 85 degrees F. In so far as chemical composition and dietetic properties are concerned, there is no distinction between the oils and the fats. The names are simply a means of ordinary discrimination which has assumed importance by reason of common usage.
There are three of the fatty acids which are particularly important from a dietetic point of view which go to make up the greater part of these fatty and edible vegetable oils and fats. These three acids are oleic, stearic, and palmitic. Of the three, oleic acid is by far the most important, as it constitutes the greater part of nearly all these bodies, especially of oils. In fact the term “olein” and oil are of common origin. Palmitic acid exists chiefly in certain forms of vegetable oil and fats, while stearic acid is a very important constituent of animal oils and fats.
These three acids uniting with glycerine form the glycerids which make up the great body of edible and animal oils and fats, and these principal glycerids are known as olein, palmitin, and stearin, respectively.
=Chemical Characteristics.=--The chemical composition of these bodies has been pointed out above. There is, however, in almost all cases, some free acid present in the compound, that is, an acid which is present uncombined with the glycerine. This free acid is usually present in small quantities and is more abundant in the overripe and older plants than in the freshly matured parts. The natural oil also contains certain other ingredients which may be regarded as impurities, and which it is necessary to remove from the oils by a process of purification or refining before they are ready for the table. These impurities may be of a mechanical nature, that is, consisting of parts of the material itself from which the oil is expressed or of certain juices not oils which are found in the animal tissue, portions of protein and other forms of nitrogenous matter, and traces of carbohydrates and gums. The oils have certain definite chemical reactions which are common to them as a class. Among these may be cited, principally, the faculty of absorbing, under certain conditions, the halogens, namely iodin, bromin, and chlorin.
Without entering into any technical description of this process it is sufficient to say here that the degree of absorption of iodin is in a measure the test for the varieties of oil. The different vegetable oils have, as a rule, certain definite relations to the absorption of iodin by means of which they may be to a certain extent identified or separated from similar bodies. The degree of absorption is expressed in the percentage by weight of the oil itself and is known as the iodin number. If, for instance, a gram of any particular oil absorbs one gram of iodin, it is said to have an iodin number of 100. Many oils absorb more than their own weight of iodin, while many others absorb very much less. Another characteristic of oil is found in the fact that with certain reagents, such as an acid either in a dilute state or in a concentrated state, definite colors are produced which are characteristic of the variety of oil in question. As an example of this may be cited the faculty which cottonseed oil has of reducing nitrate of silver to the metallic state, leaving the silver in that finely divided form which has a black color. This is the only oil in common use which has this faculty, and hence it may be regarded as a characteristic test.
Another characteristic chemical property of cottonseed oil is the color which is produced in the Halphen reaction, which has already been described.
One of the most valuable chemical properties of oil is the amount of heat which is produced when it is burned. Inasmuch as oils in relation to their food value are useful chiefly for the production of animal heat, this chemical property becomes of great hygienic and dietetic significance. Of all classes of food products the oils and fats have the highest calorific power. If, for instance, it is said in general that one gram of carbohydrates, such as sugar or starch, on complete combustion will yield 4,000 calories, one gram of protein 5,500 calories, then one gram of oil or fat will yield 9,300 calories. The fats and oils vary among themselves in respect of the number of calories yielded, but all of them give, approximately, the number last mentioned. It therefore follows that oils and fats are the most valuable constituents of food in respect of the production of heat and energy.
=Crystalline Characteristics.=--The forms of crystals which the fats assume on solidifying are valuable indicators of the nature of the oil. While these crystal forms are not in all cases distinct, yet they are influenced to a greater or less extent by the nature of the oil itself. Thus the presence of any particular oil may very often be ascertained by the examination of the crystals produced by lowering the temperature very slowly or by dissolving the oil in a volatile solvent and gradually evaporating the solvent. Tests of even greater delicacy may be obtained by first saponifying the fat or oil, separating the fatty acid, and subjecting it to crystallization.
=Distribution of Oils in Plants.=--In nearly all cases the part of the plant which contains the most oil is the seeds. In fact all of the vegetable oils which are used for edible purposes are extracted from the seed of the plant. In the case of olives the meaty portion around the seed yields the edible oil of highest value, but in all other cases of edible oils they are derived from the seeds themselves. It is a mistake to suppose that the seeds are the only parts of the plant that contain oil. It is found in all parts of vegetable substances, but is usually concentrated in the seed. It is rather an interesting fact to know that in the seeds of plants both the protein and fats or oils are found, as a rule, in a highly concentrated state, while the carbohydrates are not found chiefly in the seed itself, that is the germ, but distributed in the fleshy envelope surrounding it or in roots or tubers.
The oils and fats are almost all soluble in ether and petroleum ether, though there are some exceptions to this, as in the case of castor oil, which is also insoluble in petroleum ether or gasoline. On the contrary, oils and fats, as a rule, are not soluble in alcohol, but the fatty acids derived from them are. Castor oil is also an exception to this rule, since it is quite soluble in pure alcohol.
=Drying and Non-drying Vegetable Oils.=--It might be supposed that if one vegetable oil be edible they all would be. This would probably be the case if vegetable oils were all composed almost exclusively of the three classes of glycerids, which have been mentioned above, but such is not the case. There are other fatty acids in combination with the glycerids which exist in vegetable oils, and chief among these may be mentioned linoleic acid, which exists in considerable quantities in the oil of flax seed, and gives to it its valuable property of a drying oil which makes it so useful in the manufacture of paints. Whenever vegetable oils and fats contain any especial quantity of linoleic acid, or any other fatty acid which has drying properties, they are rendered more or less unfit for human consumption. The number of drying oils is very great, but the most important are linseed oil, hempseed oil, and poppyseed oil. Other vegetable oils have, to a certain degree, drying properties, and among those which are most marked in this particular may be mentioned cottonseed oil, sesamé oil, maize or corn oil, and rapeseed oil. Types of the oils which have the least drying properties and which are regarded as types of non-drying oils are olive oil and peanut oil. The castor oil group is distinguished partially from the other vegetable oils because it contains, or is likely to contain, more or less of a somewhat poisonous substance, namely, ricinolein, which is peculiar to castor oil and to which its purgative value as a medicine is due. The castor bean also contains a very poisonous nitrogenous base, ricin, very small quantities of which may be incorporated in the oil itself.
Melting Point and Solidifying Point.--The oils and fats differ greatly among themselves in the temperature at which they become solid or liquid. If a solid fat or oil is subjected to a gradual rise of temperature it does not pass at once or suddenly from a solid to a liquid state, but there is a gradual liquefying,--thus olein first becomes liquid and the stearin and palmitin become liquid at a higher degree of temperature. The same phenomenon in its inverse order occurs when a liquid fat is cooled until it solidifies. The moment at which the fats become semi-liquid, liquid, or semi-solid, therefore, is not to be determined with absolute precision, but only approximately, and that temperature is designated as the melting or solidifying point respectively. When the process is carefully conducted under standard conditions the different fats and oils have very definite melting or solidifying points, as determined in the manner described above, and these temperatures should be sufficient to make the melting and solidifying points valuable indications of the character or kind of oil.
=Physical Characteristics.=--The difference in the physical characteristics of vegetable fats and oils is even greater than in their chemical composition. Unfortunately for the chemist, the vegetable fats and oils naturally have about the same color or at least very slight variations therefrom, namely, an amber tint, so that, as a rule, it is impossible to discriminate between these oils by their mere color alone. The edible oils also have very much the same taste, so that this physical property is not of any very great diagnostic value. Some of the more important physical properties by which the oils are distinguished are the following:
=Refractive Index.=--The well-known phenomenon which is shown by water of bending sharply a ray of light falling upon it in a direction oblique to its surface is known as refraction, and the degree of deflection of the ray is a measure of the refractive index. This is easily illustrated by putting a straight stick or rod into still water at an angle to its surface. The stick or rod will appear to be broken or bent at the surface. Oils have a higher faculty of deflecting the ray of light than water. For instance, if in round numbers the refractive index of water is represented by 1.33, the refractive index of oil may be represented by 1.44. The oils differ greatly among themselves in the magnitude of the refractive index, but these indexes are all approximately of the magnitude last mentioned. Hence a determination of the refractive index is a valuable means of helping to discriminate between oils of different kinds.
=Reichert-Meissl Number.=--Attention was called above to the fact that in addition to three special forms of fatty acids there were many others present in oils in small quantities. Among these are found acids which are volatile in a current of steam, which is not the case with the oleic, palmitic, and stearic acids. Among the most important of the volatile acids is the one which exists in large quantities in butter, namely butyric acid. The quantity of volatile acid is determined arbitrarily by the amount of a standard alkali solution which will be neutralized by the volatile acid from five grams of fat. In the case of butter, for instance, it may be said that in round numbers it requires 28 cubic centimeters of standard alkali to neutralize the volatile acid produced according to the above method of procedure. In cottonseed oil the amount of standard solution required to neutralize the volatile acid obtained in the same way is extremely minute, amounting to less than one-half cubic centimeter.
I have given above a brief description of some of the physical and chemical characteristics of oils and fats in order that the reader not specially trained in chemistry may understand thoroughly the references made to these properties in the general description given of vegetable fats and oils. It is not necessary to be a skilled chemist in order to have a general knowledge of some of the points which are of most interest in this respect.
=Saponification Value.=--As is well known, one of the most common uses of oils and fats is in soap making. Soap consists of the products of chemical reactions by means of which the glycerine contained in an oil or fat are set free and a mineral or other base substituted therefor. For instance, lye consists of the hydrate or carbonate of potash and soda. When an oil is heated with a lye the fatty acid leaves the glycerine in the oil and combines with the potash or soda of the lye. The number of milligrams of potash or soda required to saponify one gram of fat or oil is called its saponification value. For instance, in the case of cottonseed oil it requires, in round numbers, 190 milligrams of potash or hydrate of potash (KOH) to replace the glycerine in one gram of oil. The quantity of potash required for an edible oil to make a complete saponification varies, and hence this number becomes one of the means of distinguishing between them.
=Specific Gravity.=--The relative weight of a given volume of oil compared with the weight of the same volume of water at the same temperature or at some standard temperature is known as its specific gravity. The oils and fats are universally lighter than water, and in the comparison the unit weight of water is assumed to be unity or 100 or 1000--usually unity or 1000. If the relative weight of water is unity, then the relative weight or specific gravity of oil is expressed as a decimal fraction. For instance, if water is taken as unity the specific gravity of oil equals .912; if the relative weight of water is assumed to be one thousand then the specific gravity expressed above is 912. Unless it is stated otherwise, in all references to specific gravity of these oils it is assumed that the comparison is between the unit weight of water and oil at the same temperature. This is the most convenient form for comparison for general use, though for strictly scientific purposes it is customary to refer all specific gravity numbers to water at the temperature of its maximum density, namely 4 degrees C. (39 degrees F.). At this temperature a given weight of water has its smallest volume, in other words its greatest density. When water is raised to a temperature above that mentioned, it expands and its volume becomes larger. When it is cooled to a temperature below four degrees C., its volume also expands.
The variations in the specific gravity of the common oils is not very great, and therefore the specific gravity is not the most valuable indication in discriminating between these oils.
EDIBLE VEGETABLE OILS.
While there is very little chemical difference between the fats of animals and the oils of plants, the difference is sufficiently distinguished to secure a proper degree of identification and classification. Both classes of bodies are composed of the fatty acids combined with glycerine. The three fatty acids which are most important from the edible point of view and also from the chemical are oleic, stearic, and palmitic. When these acids are united with glycerine as the basic element, they form three classes of oils or fats to which the names olein, stearin, and palmitin are respectively given. A distinction may also be made between a fat and an oil by observing its physical consistence at ordinary room temperature of approximately from 70 to 80 degrees F. It is usual to speak of the bodies which are liquid at such temperature as oils, while those that are solid under like conditions are known as fats. A compound of this description does not pass suddenly from one state to another. In the case of a fat, for instance, which is solid at ordinary temperature, it passes by gradual stages from that condition to a slowly softening mass and then to a complete liquid as the temperature is raised. On the other hand, an oil passes gradually through the same stages to the condition of a solid body as the temperature is lowered. Of the different constituents the olein has the lowest melting point, pure olein being still liquid at quite a low temperature, approaching even the freezing point of water. Stearin and palmitin on the contrary, if in a pure state, are solid at a temperature even above that of the room and above that of blood heat. In the mixture of these bodies it is evident that a complicated structure must be present which is composed of different bodies of varying melting points and passing through all different degrees of temperature from a solid to a liquid state or vice versâ. It is evident that an oil has a larger proportion of olein in its composition and a fat a larger proportion of stearin and palmitin.
Animal fats are composed chiefly of olein and stearin, while strictly vegetable oils are principally olein, and palm oil is composed chiefly of stearin and palmitin.
In butter fat there is introduced an important additional compound of a fatty acid with glycerine, namely butyrin, which is made up of a union of glycerine with butyric acid. Butter also contains other components or glycerids, but in small quantities. Oleic, stearic, and palmitic acids are insoluble in water and not volatile at the boiling point of water. Butyric acid is soluble in water and is volatile at the boiling point of water. The first kinds of acid are therefore called “fixed” and the second “volatile.”
The edible vegetable oils like the animal fats are highly nutritious in the sense that they afford to a greater degree than any other kind of food product the elements necessary to the production of heat and energy. The average number of calories to one gram of edible oil is in round numbers 9,300. When this number is compared with the average number of calories in one gram of sugar or starch, namely 4,000, it is seen that fats and oils are two and one-fourth times as valuable as sugar in the production of heat and energy. Since the greater part of the food consumed by an animal is utilized in the production of heat and energy, it is seen that the fats and oils must be classed as the most concentrated and in that sense the most valuable human foods.
The use of edible vegetable oils is also advisable for hygienic purposes. They are readily assimilated and digested, and they produce a physical effect upon the process of digestion which is a matter of importance. The free use of edible vegetable oils is to be recommended in cases of constipation or where there are mechanical difficulties in the digestive process. In these cases it is consumed in larger quantities than would ordinarily be the case.
=Use of Edible Oils.=--The edible oils are used most extensively on the table as the base of salad-dressing. Many succulent vegetables, as has already been stated, are eaten very commonly with condimental substances such as vinegar, salt, spices, etc., and as a vehicle for these condimental substances there is nothing superior or even equal to the edible vegetable oils. Vinegar, itself, owes its active principle, namely, its acid, to a member of the fatty acid series, so that the mixture of vinegar with oil is not a bringing together of two wholly different substances but of two substances belonging to the same general family. Vinegar itself has no value as a food, but is useful solely for condimental purposes. On the other hand the edible oil is not only condimental, increasing the pleasant taste of the compound, but also has a high food value. Edible oils may also be used in the place of lard and other animal fats in the preparation of bread and pastry, serving the purpose of shortening. Edible oils are also highly useful as a vehicle for frying foods, such as oysters, croquettes, doughnuts, etc.
The heating of an oil or fat to a high temperature produces a certain degree of decomposition with a development of an aromatic and sometimes unpleasant product known as acrolein. It is not believed that this change is as detrimental to digestion as is commonly supposed. Products which are fried in oil, or boiled in oil, which is probably a better term, as described above, are not to be considered wholly indigestible, though it cannot be denied that they are not the best things for delicate stomachs or those which are in any way weakened by disease. In the case of a healthy individual, however, a moderate quantity of such products may be eaten without any great danger of producing a derangement of digestion. If these bodies are found to be indigestible, it is probably not due to the fact that they contain large quantities of oil but rather to the decomposition effected by the high temperature and the hardening of the periphery of the bodies to such an extent as to make them difficultly amenable to the activities of the digestive ferments.
=Acorn Oil.=--The oil of the acorn is sometimes used for edible purposes. It is extracted by pressure, and the nature of the product depends upon the variety of the acorn. Acorn oil has at 15 degrees a specific gravity of .916 and an iodin number of 100. It is not of any commercial importance as an edible oil.
=Almond Oil.=--Almond oil is not so commonly used for edible purposes as it is for pharmaceutical preparations. By reason of its flavoring properties, however, it may sometimes be used for food purposes, and a brief description, therefore, is advisable.
Almond oil is obtained from the seed of the bitter almond, a variety of Amygdalus communis L. It may also be extracted from the seeds of the sweet almond, but these contain less oil than the bitter almond seed and the oil is not so useful for flavoring purposes. The bitter almond whose seeds are used for the extraction of oil are grown chiefly in Morocco, the Canary Islands, Portugal, Spain, France, Italy, Sicily, Syria, and Persia. The almond kernel contains about 40 percent of oil. Almond oil is said by most observers to be free from stearin, and it is therefore an oil which is composed almost exclusively of olein. The specific gravity of almond oil at 15 degrees C. is almost exactly that of rapeseed oil, being only a trifle higher. The average number expressing the specific gravity at that temperature is .918. Its iodin value is slightly lower than that of rapeseed oil, being about 97.
Adulterations.--Almond oil is often adulterated with other cheaper oils. Among these those which are principally used are cottonseed oil, walnut oil, poppyseed oil, sesamé, peanut, apricot-kernel and peach-kernel oil, and lard oil. Those most frequently used are the apricot and peach, since these oils contain the characteristic principle which gives the bitter taste to the kernels of this class in fruits. Often almond oils are offered to the trade which are composed exclusively of peach-kernel or apricot-kernel oil. Whenever the iodin number of an almond oil runs very high it is an indication that it is composed largely of peach or apricot oil. The detection of small quantities of these oils when added to almond oil is a very difficult matter and can only be accomplished by the expert chemist.
=Cottonseed Oil.=--One of the most important edible oils in the world, and especially from the point of view of production in the United States, is that derived from the seed of the cotton plant (Gossypium herbaceum).
The cotton plant grows over a wide area in the United States, including all of the southern states and extending into southern Virginia, southern Kentucky, southern Missouri, and Oklahoma. In former years the cotton plant was cultivated solely for its fiber. It is only in the last quarter of a century that the high value of its seed for many purposes has been realized. The seed of the cotton plant is preëminently rich in oil and protein. It contains traces of certain poisonous alkaloids, betain and cholin, the presence of which renders its indiscriminate use for cattle food in some cases dangerous. In the preparation of oil, however, no trace of these poisonous substances is found, since they exist solely in the non-fatty tissues of the seed. The production and refining of the oil has now grown to be a great industry and has already added much to the wealth of the cotton growers and the comfort and nutrition of the people in general.
Magnitude of the Cottonseed Oil Industry.--The average cotton crop of the United States is about 12,000,000 bales of about 500 pounds each. For every bale of cotton there is produced 1,000 pounds of seed. This would make the average cottonseed crop of the country about 6,000,000 tons. It is estimated that not over two-thirds of this is used in the mills; this would make about 4,000,000 tons. The average yield of 40 gallons to a ton shows the production of crude oil to be 3,200,000 barrels of 50 gallons each. This oil in refining loses on the average about 8 percent, which would leave 2,944,000 barrels of refined oil for edible and other purposes. Not less than two-thirds of this oil is used for edible purposes. A conservative estimate would place the quantity used for food between two millions and two millions and a half barrels per annum. The quantity varies with the prices of other fats.
Cotton seed is brought to the mills from the gins either by rail in box cars or in wagons. On arrival at the mills, it is stored in large sheds, known as seed houses. A single seed house will often contain as much as 5,000 to 10,000 tons. The seed is carried into the mill by means of conveyers. It first goes through coarse screens which remove the greater part of the trash and sand, after which it is passed over magnetized iron plates which remove nails and pieces of iron which may have accidentally gotten into the seed. After the seed is thoroughly cleaned it passes through gins known as linters, which remove from 40 to 50 pounds of short staple cotton known in the trade as “linters.” This cotton is used for preparing cotton batts, mattresses, etc. Conveyers carry the seed from the linters to the hullers, which are rapidly revolving drums covered with cutting knives which chop up the seed. From the hullers the cut-up seed pass over a series of screens where the meats are shaken out while the conveyors carry the hulls to a suitable store house. The hulls are used for cattle food. The meats are carried to the crusher rolls, through which they pass. These rolls break up oil cells to a large extent and leave the meats in a finely divided condition. From the crusher rolls the meats are carried to steam-jacketed kettles provided with agitators. There they are cooked to the proper point, which is determined by feel and smell. From the heaters the meats are dropped into cake formers, where they are formed into shape of cakes between camel’s hair press cloths in which they are placed in the heavy hydraulic presses which press out the oil. Good press-room work will give out 45 gallons of oil to the ton and leave in the cake between 6 and 7 percent of oil.
The crude oil as it leaves the presses varies in color from light sherry to deep claret. The variation is due to local conditions affecting the seed, also the manner of treatment in cooking. The flavor of the crude oil varies greatly in the different parts of the country. That made in Georgia and Carolina has a strong flavor of peanut, while that made in the Mississippi Valley and Texas has more the flavor of sweet Indian corn.
To prepare crude oil for edible purposes, it must go through a process of refining; this is accomplished by agitating in large tanks with caustic soda solution. When the soda is added in the proper amount, the coloring matter, free fatty acids, and vegetable matter contained in the oil are converted into a mucilaginous soap which separates in dark-colored flakes through the oil when heat is applied. When the granulation has reached the proper point, agitation is stopped, and the flaky soap stock settles at the bottom of the tank, leaving a clear, light, greenish-golden oil on top. The best practice allows tanks to settle about 12 hours, after which the soap stock has drawn off and the well settled yellow oil is removed to a settling tank where it is gently heated to remove moisture and remaining soap stock. This produces what is known as prime summer yellow oil. This oil has a sweet flavor and light yellow color. Unfortunately when used for cooking it gives off a very disagreeable odor and leaves a bad flavor in the article of food cooked with it. This renders further purification necessary. The oil is heated to temperatures varying from 150 to 200 degrees F. and agitated in kettles with fuller’s earth, after which it passes through filter presses, which remove the fuller’s earth and leave the oil very nearly white. In this condition the oil is still unfit for cooking purposes, on account of the peculiar flavor given by the fuller’s earth treatment, which is commonly removed by treatment with steam. Details of this deodorizing process vary and are regarded as trade secrets. The oil so prepared is largely used in the preparation of substitutes for lard and similar cooking fats. Such oil is a great improvement over the ordinary summer yellow and bleached oils, but falls short of being an ideal oil.
Within the last few years a cottonseed oil has been put on the market in which the objections to the use of cottonseed oil as food have been as nearly overcome as the chemical nature of the oil will permit. The oil produced by this process is practically odorless and tasteless and can be used satisfactorily for all culinary purposes. Large quantities are used by the bakers in place of lard. (David Wesson.)
Further Details.--The cotton seed from various sources is put through a screen to take out the bolls and coarse material. The seed is then put through a gin to remove as far as possible any remaining lint, of which about 20 pounds per ton of seed are obtained. The clean seed is next sent to a huller composed of revolving cylinders covered with knives, which cut up both seed and hull. The chips are then conveyed to a screen placed on a vibrating frame, through which the kernels fall. The hulls are carried by an endless belt to the furnaces, where they are burned. The kernels of the seed are conveyed to crusher rolls, where they are ground to a fine meal. The meal is then sent to a heater, where it remains from twenty to forty minutes. These heaters have a temperature of 210 to 215 degrees F.
The hot meal is formed into cakes by machinery; these are wrapped in cloth and placed in the press. About sixteen pounds of meal are put in each cake. The cakes are placed in a hydraulic press, where a pressure of from 3,000 to 4,000 pounds per square inch is applied. The press is also kept warm. The expressed cakes contain only about 10 percent of oil. The cake is sold as cattle food or for fertilizing purposes. The crude oil as thus expressed contains about 1.5 percent of free acid, also a notable quantity of water and solid matters in suspension. The manufacture of cottonseed oil usually takes place in the winter months immediately after the ginning of the cotton is completed. The oil is likely to become rancid if kept unpurified until the hot months. The crude oil is collected in oil tanks at the press and shipped to the refining houses. In winter time when tanks are sent to the north where the temperature is very low the contents of the tank become solid unless protected from the action of the cold.
Refining Process.--The first step in the refining of a crude cottonseed oil is to have it stored in large and deep tanks where it remains at rest for a proper length of time. During this period of rest the heavy mechanical impurities and water settle to the bottom of the tank and are typically known as “foots.” The oily portions of these fats are used in the manufacture of soap and for other technical purposes. The tanks may be connected with steam jackets in order to keep the oil at a proper temperature. During the process of deposition the oil is also treated with an alkali to neutralize the free acid which it contains. The precipitate formed by this process together with the principal part of the soaps produced are recovered with the “foots.” A solution of caustic or carbonated soda is one generally employed in this process of refining. If the admixture of caustic soda occurs at the time of filling the tank, the contents are kept well agitated for a sufficient length of time to secure an intimate mixture of the oil with the lye. Usually the deposition of the solid matter is accomplished in from two to three days. The supernatant oil is of a light yellow color, but not sufficiently pure to admit of being used for edible purposes. This yellow oil is treated again in a similar manner and allowed to settle a second time, or it is mixed with some substance which will facilitate the operation, and subjected to filtration by means of which a perfectly bright oil is secured. If, during this process, the oil has never been chilled so as to separate a part of its stearin, it is called summer oil, as an indication that it only remains clear during the hot weather. Oils intended for winter use are chilled before finally being put into packages, and the stearin which is separated at this low temperature is removed by filtration. The residual oil which is capable of remaining liquid at a low temperature by reason of the removal of a portion of its stearin, as above described, is known in the trade as winter oil. In this process of filtration fuller’s earth is frequently employed, which not only promotes the filtration but also absorbs and retains a large part of the color of the oil, which thus treated is almost colorless. Where cottonseed oil is used for mixing with lard it is highly important that it be practically free of color. When, however, it is used for mixing with oleomargarine the more yellow it is the more highly prized.
Extraction of Oil by Means of Petroleum.--The light oils which are produced in the refining of petroleum and commonly called gasoline are typical solvents for fat and oil. Instead of extracting the oil by the pressure process, as described above, a practically complete extraction may be secured by successive treatments with the light petroleum oils. The principle of the process is exactly that of the extraction of sugar from sugar beets by hot water in the process of the manufacture of beet sugar. The cottonseed cake or pressed meal is broken into fragments of approximate size, placed in tanks, and treated with successive portions of light petroleum. The extraction is arranged in such a way as to be a continuous one, that is, the vessels for handling the oil cakes are arranged en batterie as in the case of beet sugar extraction. By this method all except a mere trace of the oil is extracted from the cake. The light petroleum oils are subsequently separated from the cottonseed oil by distillation and are used again in the process. There is little loss of petroleum oil. Where cottonseed oil is used for technical purposes there is no objection to this method of extraction, and much is to be said in its favor since greater yields of oil are secured. When used for edible purposes, however, petroleum extracted cottonseed oil is not of as high a quality as that extracted by pressure. It is difficult to remove all traces of petroleum, especially the odor, and there are constituents extracted by petroleum which are not mixed with the oil when it is separated by pressure. It is advisable, therefore, that cottonseed oil used for edible purposes be cold-press extracted and not petroleum extracted oil.
Standard for Cottonseed Oil.--The official standards for cottonseed oil are as follows:
“Cottonseed oil is the oil obtained from the seeds of cotton plants (Gossypium hirsutum L., G. Barbadense L., or G. herbaceum L.) and subjected to the usual refining processes; it is free from rancidity; has a refractive index (25 degrees C.) not less than one and forty-seven hundred ten-thousandths (1.4700) and not exceeding one and forty-seven and twenty-five ten-thousandths (1.4725); and an iodin number not less than one hundred and four (104) and not exceeding one hundred and ten (110).
“‘Winter-yellow’ cottonseed oil is expressed cottonseed oil from which a portion of the stearin has been separated by chilling and pressure.”
=Hazelnut Oil.=--The oil of the hazelnut is to a limited extent used for edible purposes. It is extracted from the seed of the hazelnut tree (Corylus avellana L). The seeds are very rich in oil and are said to contain from 50 to 60 percent thereof. The oil is almost free of stearin and is said to contain only about one percent. The rest of it consists chiefly of olein, there being but 12 percent of palmitin. While it is an edible oil, it is used chiefly in the manufacture of perfumes and as a lubricating oil. Its high price, however, excludes it from any general use, except for special purposes. Its specific gravity at 15 degrees is .916, and it absorbs about 86 percent of its weight of iodin.
=Olive Oil.=--By far the most important of edible oils, both on account of its abundance and of its palatability, is olive oil. Olive oil has been used from the earliest historical times and probably was the first vegetable oil that was manufactured to any considerable extent in the early history of civilization. Its qualities have maintained for it a market among the nations of the world in spite of the fact that many other palatable and wholesome vegetable oils have been produced which, while not inferior in nutritive value to olive oil, are so very much cheaper that unless the olive oil possessed peculiar properties it would be forced out of the market. Its delicate flavor, extreme palatability, high nutritive power, and other general characteristics have maintained for it a market against the strongest competition.
Olive oil is procured from the fruit of the olive tree (Olea Europæa L.), and when it is to be used for edible purposes the method of extraction is by pressure. When olive oil is used for technical purposes, such as lubricating and the manufacture of soap, it is very commonly secured by extraction with a volatile solvent, such as petroleum. The olive is very rich in oil, the quantity varying from 40 to 60 percent. The quality of olive oil upon the market varies in a very great degree according to the country from which it comes, the degree of maturity of the olive from which the oil is extracted, the method of expression employed, and the character of the refining process to which the expressed oil has been subjected. Botanically, there are very many varieties of olive trees and thus nature would impart to the olive peculiarities due to the origin of the oil itself. The environment also has a great deal to do with the character of the olive and necessarily with the character of the oil produced. The olive tree flourishes best in semi-arid regions where the rainfall is not very abundant and the sunlight is not greatly obscured by clouds and the heat is reasonably high. The principal regions, at the present time, from which the commercial olive oils are obtained are Spain, Italy, Greece, southern France, and southern California.
Adulteration of Olive Oil.--By reason of its great value as an edible oil and its high price there is no one of the edible oils which has been subjected to such a systematic and extensive adulteration. By reason of the resemblance in general character of many of the edible vegetable oils to olive oil, adulterations of the most extensive character may be practiced without indicating to the eye any change in composition. Nearly all the edible vegetable oils have the light amber tint which is characteristic of many grades of olive oil, and the difference between the color of the olive oil and other edible oils is not greater than the difference between the tints of the various olive oils themselves. The connoisseur of extremely delicate taste is usually able to distinguish by the taste any given edible oil from olive oil. If, however, any given edible oil be mixed with olive oil in small proportions not exceeding 25 to 30 percent, even the skilled taster will be deceived. In such cases only the chemist who has much skill and practice is able to detect the adulteration.
Adulteration with Cottonseed Oil.--In the United States the principal adulteration of olive oil is with cottonseed oil. This is an oil which has already been described as of high nutritive value and to which no objection can be made from any hygienic or dietetic point of view. It is made in great quantities in the United States, and when subjected to the most careful refining processes can be offered to the consumer at a price probably not greater than one-fifth that of high-grade olive oil. It becomes the ideal material with which to adulterate olive oil. This adulteration extends often to complete substitution, the oil in question, though represented as olive oil both by the dealer and the label, containing no trace whatever of that substance. Such bare-faced substitution has apparently almost passed away under the quickening ethical sense of the manufacturer and merchant and the character of the national and state laws. Many of the oils which are used to adulterate olive oil have a greater specific gravity, hence whenever the specific gravity of an olive oil at 15 degrees goes above .917 it is ground for suspicion of adulteration though by no means a positive proof. The presence of cottonseed oil in olive oil is easily detected by the Halphen test, which has already been described. In Europe a very common method of adulteration is with sesamé oil, the properties of which are described below. Peanut oil is also extensively used for the same purpose. These two oils are easily detected when mixed with olive oil. The sesamé oil is distinguished by the color reaction to be described. Peanut oil is distinguished by the saponification of the oil, separation of the fatty acids, and consequent crystallization of the arachidic acid, which produces a crystalline form which is readily recognized by an expert. Rapeseed oil and poppy-seed oil are also extensively used as adulterants in Europe, but not very extensively in this country. Nearly all the oils which are employed in the adulteration of olive oil have high iodin numbers, and therefore whenever an iodin number is above 89 or 90 it may be regarded as a suspicious circumstance. There are, however, many genuine olive oils which would be condemned as adulterated if this test alone were employed. In addition to the oils mentioned, small quantities of castor oil, lard oil, fish oil, and even of petroleum oil, have been found as adulterants in olive oil. These, however, occur very infrequently, and it is not likely that they have been employed in this country.
If the examination shows that a given sample is free of cottonseed, sesamé, and peanut oil, and other characteristics in the sample are those of olive oil, it may be safely accepted as a pure sample.
Color of Olive Oil.--The color of the freshly expressed olive oil is usually green or dark from the chlorophyl and other coloring matter derived from the olive. When refined and ready for commerce the oil is of a yellowish-green tint usually. Sometimes the oil obtained from the first pressing is almost colorless, but as a rule an amber-green tint is observed in most of the commercial varieties. Lower grade oils are often decidedly green, but still edible, due to the admixture of chlorophyl from the green olive employed. The flavor of olive oil is a pleasant and agreeable one, but differs greatly in oils from different sources. The further north the oils are produced the less pronounced the flavor and the sweeter the taste. The more southern oils, such as are obtained in the south of Italy and Spain, have a stronger and more pronounced flavor which, however, is very much prized by those accustomed to it. Large quantities of olive oil are produced also in the French and other possessions in the north of Africa. These, however, have a stronger flavor than those produced upon the continent of Europe and are not so highly prized when used alone. Olive oil is almost free of stearin, being composed chiefly of olein with some palmitin. The amount of free acid in olive oil varies with the character of the olives employed and the age of the oil. On long standing, without becoming rancid, olive oil develops a large quantity of free acid. It is a common supposition that rancidity in an oil depends upon the development of free fatty acid, but this is not the case. If an oil be free of rancidity it may contain a large percentage of free acid without becoming inedible. It is not uncommon to find in olive oil as high as 3 percent or more of free acid. This is due to the fact that in the refining of olive oil alkalies are not usually employed, and therefore any free acid which the natural olive possesses is not neutralized by the alkalies, as is the case in the refining of cottonseed oil and some other vegetable oils.
Constituents of Olive Oil.--Olive oil consists almost exclusively of olein and palmitin. There is very little, if any, stearin in the highest grade oil. If all the solid fatty acid at ordinary temperature be regarded as derived from palmitin, the quantity of palmitin may be regarded as varying from three to 20 percent, according to the origin and character of the sample. While the olein and palmitin, therefore, may be regarded as the principal constituents of olive oil, there are others, also, existing in smaller quantities. The quantity of free fatty acid varies very greatly in olive oil. It is highly important that the oil be separated from the pomace as speedily as possible, since any fermentation of the pomace increases the quantity of free fatty acid. The largest number of high-grade oils contain less than three percent of free fatty acid, but a larger quantity, as has been stated, does not render the oil inedible unless actual fermentation has taken place producing rancidity. Rancidity appears to be the result of the generation of other acids than oleic, and also aldehyds, formic, butyric, acetic, and œnanthylic acids have been found. Olive oil is a typical non-drying oil and therefore shows a less rise in temperature when mixed with sulfuric acid than other vegetable oils. The specific gravity of olive oil at 15 degrees may be placed at the average figure of .917. It sometimes falls as low as .912 and rises as high as .919. It absorbs from 80 to 90 percent of its weight of iodin. In some samples the weight of iodin absorbed is less, falling as low as 77 percent, but this is only in very extraordinary cases. Occasionally it goes above 90 percent. Probably the number 87 would represent about the mean percentage of iodin absorbed by most edible oils.
Method of Preparation.--The very finest quality of olive oil is that derived from the hand-picked olive. Just as in the preparation of fruits for the market the very best qualities are carefully picked one by one from the tree, so in the preparation of the highest grade of oil the olives are picked one by one, only those of uniform maturity and character being selected. This specially selected fruit is pressed cold, and the first running from this pressure collected separately is designated in English by the term “virgin oil.” Virgin olive oil, therefore, ranks the highest in quality. Unfortunately the use of the term for commercial purposes has not been restricted to the quality of oil to which it actually belongs, and at the present time the expression “pure virgin olive oil” which is placed upon the bottles or containers is no guarantee that this quality of oil is found therein. In fact, this expression upon the label has been found in many instances of olive oil highly adulterated and belonging to the cheapest grade. It would be impossible here to enumerate all the different names by which olive oil is found upon the market. The consumer has to depend for protection upon his knowledge of the character of the dealer and hereafter, to a greater extent than ever before, he may be protected by the application of the pure food laws of the various countries.
After the first pressing from which the best oil is secured the resulting pomace is removed from the press, heated or mixed with hot water, and again subjected to a much higher pressure from which a second quantity of oil is secured, still suitable for edible purposes but of a lower quality than that first produced. While the oils which are obtained in this way are used largely for technical purposes such as lubricating, soap making, etc., they are not infrequently employed as edible oils.
In the largest establishments for the preparation of olive oil the kernels are separated from the pulp, but in the smaller works the pulp and kernel are pressed together. Finally the residue from the second pressure may be dried and extracted with bisulfid of carbon or petroleum ether, by which means practically all the residual oil which the cake contains may be secured. Oils extracted in this manner are wholly unfit for edible purposes and are used or should be used solely for technical purposes, among which soap making is perhaps the most important.
Olive-kernel Oil.--An oil is extracted from the kernel of the olive which in some respects of physical and chemical properties resembles olive oil itself. It is usually not considered suitable for edible purposes. Its taste resembles more that of almond oil than that of olive oil. Some of this oil is doubtless mixed with olive oil when the pulp and kernel of the olive are pressed together, but the quantity thus secured is not very great and does not introduce into the substance anything which gives a specific reaction. It is by no means as high a grade of oil as that expressed from the flesh of the olive alone.
=Peanut Oil.=--Peanut oil is the refined expressed oil of the peanut, prepared in the manner above described, and is highly valued as a table or salad oil and, unfortunately, is used very often as an adulterant of olive oil, the mixture being sold under the name of the more valuable of its constituents.
Peanut oil contains arachidic acid, which in combination with glycerine forms one of the constituents which serves to distinguish it particularly from other edible oils. There is no other edible oil which contains arachidic acid in sufficient quantities to lead to any mistake concerning its relationship to peanut oil.
Renard’s Test for Peanut Oil as Modified by Tolman.--Place 20 grams of oil in an Erlenmeyer flask. Saponify with alcoholic potash, neutralize exactly with dilute acetic acid, using phenolphthalein as indicator, and wash into a 500 c.c. flask containing a boiling mixture of 100 c.c. of water and 120 c.c. of a 20 percent lead acetate solution. Boil for a minute, and then cool the precipitated soap by immersing the flask in water, occasionally giving it a whirling motion to cause the soap to stick to the sides of the flask. After the flask has cooled, the water and excess of lead can be poured off and the soap washed with cold water and with 90 percent (by volume) alcohol. Now add 200 c.c. of ether, cork the flask, and allow to stand for some time until the soap is disintegrated, then heat on the water bath, using a reflux condenser, and boil for about five minutes. In the oils most of the soap will be dissolved, while in lards, which contain so much stearin, part will be left undissolved. Cool the ether solution of soap down to from 15° to 17° C., and let stand until all the insoluble soaps have crystallized out--about twelve hours are required.
Filter and thoroughly wash the precipitate with ether. Save the filtrate for the determination of the iodin number of the liquid fatty acids by the Muter method. The soaps on the filter are washed back into the flask by means of a stream of hot water acidified with hydrochloric acid. Add an excess of dilute hydrochloric acid, partially fill the flask with hot water, and heat until fatty acids form a clear, oily layer. Fill the flask with hot water, allow the fatty acids to harden and separate from the precipitated lead chlorid; wash, drain, repeat washing with hot water, and dissolve the fatty acids in 100 c.c. of boiling 90 percent (by volume) alcohol. Cool down to 15° C., shaking thoroughly to aid crystallization. From 5 to 10 percent of peanut oil can be detected by this method, as it effects a complete separation of the soluble acid from the insoluble, which interferes with the crystallization of the arachidic acid. Filter, wash the precipitate twice with 10 c.c. of 90 percent (by volume) alcohol, and then with alcohol of 70 percent (by volume). Dissolve off the filter with boiling absolute alcohol, evaporate to dryness in a weighed dish, dry and weigh. Add to this weight 0.0025 gram for each 10 c.c. of 90 percent alcohol used in the crystallization and washing if done at 15° C.; if done at 20°, 0.0045 gram for each 10 c.c. The melting point of arachidic acid obtained in this way is between 71° and 72° C. Twenty times the weight of arachidic acid will give the approximate amount of peanut oil present. No examination for adulterants in olive oil is complete without making the test for peanut oil.
The above process to be of any particular value can only be carried out by an experienced chemist, but the presence of peanut oil may be readily determined by any one who is experienced by following out the above process.
Where only small quantities of peanut oil are concerned, namely, not to exceed five percent, even in the hands of an experienced chemist, the above process may not lead to certain results.
Peanut oil is obtained from the peanut by the ordinary method of hydraulic pressure. The first cold pressing furnishes the oil of finest character for edible purposes. Subsequent pressures or pressure with heat furnish an additional supply or a great quantity of oil but not of the same palatability. Peanut oil is highly prized as a salad oil either alone or mixed with other oil, notably olive oil and sesamé. The oil is purified by a large settle and by filtration and by the processes usually practiced with other oils of vegetable origin. The oil is easily and completely digested and furnishes an abundant source of heat and energy to the system. The number of calories produced by the combustion of one gram of oil, either by ordinary burning or by oxidation in the body is about 9,300.
The cake which is left after the pressing out of the oil is very highly nutritious, containing still considerable quantities of oil, the whole of the protein matter, and other digestible solids of the nut.
As before stated, it is extensively used as cattle food and as fertilizer. It may also be ground to a meal and used as human food, but furnishes an unbalanced ration in which the protein is far in excess.
=Rape Oil= (=Colza Oil=) (Brassica campestris L.).--There are different kinds of oil which belong to the general class which is known as rape oil or rapeseed oil. The different kinds are derived from different varieties of Brassica campestris. The English names of the three most important varieties are--(1) colza oil, derived from the seeds of Brassica campestris; (2) rape oil, derived from the seeds of Brassica napus L.; (3) rübsen oil, derived from the seeds of Brassica rapa L. The character of the oil also varies according to the manner of its extraction. The first pressings from the cold powdered seeds is of a finer quality for salad purposes than the heavier later pressings from the hot seeds. The oil is also sometimes chilled and the crystallized stearin separated in order to keep it in a liquid state during the winter time, so that the winter and summer varieties are sometimes recognized in trade. There is, however, no difference in the other characteristics of the oil.
The specific gravity of rape oil at 15.5 degrees C., compared with water at the same temperature, is about .916. The variations from this mean number are not very great. Rapeseed oil absorbs almost its exact weight of iodin,--the average iodin number being not far from 99.
The Chief Adulterations of Rape Oil.--The chief adulteration of rape oil consists in the admixture of cheaper or flavoring oils. Among those which are often used in the adulteration of rape oil are linseed oil, hempseed oil, poppy-seed oil, chamomile oil, cottonseed oil, the various mustard oils, refined fish and blubber oils, rosin oil, and paraffin. Some of these adulterations, it is seen, cannot be added to rapeseed oil when used for edible purposes. The chief adulteration of rapeseed oil, when intended for edible purposes, is the addition of cottonseed oil. The detection of these various adulterations, with the exception of that of cottonseed oil, can be accomplished only by an expert chemist. The presence of cottonseed oil can be detected by the application of the Halphen test already described.
Technique of Extraction.--The extraction of oil from the rape seed is not different from that of other oily seeds. It is either extracted by pressure, which is the proper way always when it is to be used for edible purposes, or when used for technical purposes it may be extracted by means of carbon bisulfid or petroleum ether. When extracted by pressure for edible purposes the oil should be refined by a similar treatment to that applied to cottonseed oil and finally filtered, preferably after mixing with fuller’s earth or other similar material, in order that it may be perfectly pure and bright and free from suspended matter which interferes with its utility as an edible oil.
A very common treatment of the expressed oil, in order to coagulate and separate the mucilaginous matter which it contains, is with sulfuric acid. This acid has the very valuable property of coagulating this class of bodies. When treated with sulfuric acid it is necessary that the oil be thoroughly washed many times in pure water in order to remove the last trace of the acid.
The residue or oil cake is prized as a cattle food or as a fertilizer. The average content of oil in rape seed is about 37 percent.
=Sesamé Oil.=--Sesamé oil is very commonly used for salad oil and for the other purposes to which the edible oils are devoted. It is also known as gingili oil and teel oil. Sesamé oil is obtained by pressure from the seed of the sesame plant,--Sesamum orientale L.
Sesamé oil possesses a light amber color when properly made, is free from any unpleasant odor, has an agreeable taste, and when expressed cold produces what is known as the cold-drawn oil which is regarded by many as of equal palatable value with olive oil. Sesamé oil, in addition to containing stearin, palmitin, and olein, also contains a small quantity of a glycerid which exists in large quantities in flaxseed oil, namely, linolein. When prepared for edible purposes it contains only a small quantity of free acid, is free from rancidity, clear, and brilliant in appearance and has a sweet agreeable taste. The specific gravity of sesamé oil at 15 degrees C. varies from .9225 to .9237. It absorbs from 103 to 108 percent of its weight of iodin and has a refractive index at 15 degrees of about 1.4748.
Adulteration of Sesamé Oil.--Some of the other vegetable oils are cheaper than sesamé and are added to it for the purpose of adulteration and cheapening the product. Among the most common oils used for the adulteration of sesamé are poppyseed oil, cottonseed oil, and rape oil. The presence of cottonseed oil in sesamé oil is easily distinguished by the Halphen test already given. The presence of poppyseed oil is revealed by the high iodin number and the high degree of heat produced when mixed with sulfuric acid.
Only the best variety of cold-drawn sesamé oil is used for edible purposes and for making oleomargarine. The inferior qualities are used in soap making, the making of perfumes, etc., and the lowest quality of oil is used for burning purposes.
Characteristic Reaction.--A test which is known as Baudouin’s is extremely delicate and reliable and is easily applied. It consists in the development of a red color when a small quantity of sesamé oil is treated with hydrochloric acid in the presence of furfural. The test is easily carried out as follows: Place a few drops of a two percent solution of furfural in a test-tube with 10 cubic centimeters of sesamé oil or the oil to be tested for sesamé and 10 cubic centimeters of hydrochloric acid of 1.19 specific gravity, and shake the mixture well for half a minute. When the tube is left at rest, if sesamé oil be present the aqueous acid layer which forms will have a distinct crimson color. Any coloration which is produced by other oils is entirely distinct from this one and therefore can be easily distinguished.
Geographical Distribution.--The sesamé plant is grown chiefly for commercial purposes in India, China, Japan, and West Africa. The technical preparation of the oil, in so far as is known, is not practiced in the United States. It is pressed and prepared for commerce chiefly in France. The seeds are rich in oil, yielding a larger percentage by pressure or extraction than most of the oil-bearing seeds.
=Sunflower Oil.=--The oil extracted from the seed of the sunflower is of high quality for edible purposes. Although not in general use in this country, it is very extensively used in Russia and some other parts of Europe. There is every reason to believe that a profitable industry could be established in the preparation of edible oils from sunflower seeds. The plant grows in the greatest luxuriance in nearly all parts of the country, and the yield is sufficiently great to make it an object of more interest to our agricultural population than it is at the present time.
The oil is obtained from the seed of the sunflower (Helianthus annuus L.). It is of a pure amber tint with an agreeable odor and pleasant taste. As has already been said it is grown largely in Russia and also in Indo-China. The seeds are very rich in oil. Before expression the hulls should be removed, since these form a porous substance, and if the seeds are crushed with the hulls large quantities of oil are absorbed and cannot be recovered.
The method of preparation is the same as that for other edible oils, the kernel, after the removal of the hull, being ground and cold-pressed for the highest grade. By heating and renewing pressure lower grades of oil are secured suitable for soap making. Where all the oil is required the extraction with bisulfid of carbon or gasoline is advised. Such oils, however, are not suitable for edible purposes because of the difficulty of removing the last traces of the solvent. The specific gravity of sunflower oil at 15 degrees is approximately .925. It absorbs a very high percentage of iodin, and in this respect it may be classified with the drying oils. Its iodin number ranges from 120 to 130. No specific color reactions have been established by means of which sunflower oil may be readily distinguished from the other edible oils.
In fact sunflower oil has not been subjected, by any means, to as critical a study as many other vegetable oils.
VEGETABLE FATS.
The fatty principles in vegetables which are solid at ordinary temperatures are commonly termed fats instead of oils. They present, as a rule, a soft mass, usually of an amber tint and somewhat of the consistence of butter. Only a few of these solid fats or semi-solid fats are used for food. Among them the most important are palm-nut oil or coconut oil or fat, though the fat of the cacao also may be regarded as belonging to this group. These solid or semi-solid fats are used to a considerable extent for edible purposes in many parts of the world. Coconut fat and cacao fat are used very extensively in this country either in a pure state or in chocolate or cocoa.
=Cacao Butter.=--Cacao butter is the semi-solid fat obtained by pressure from cacao beans, the seeds of the cacao tree (Theobroma cacao L.). These beans are extremely rich in fat, the content of which varies from 35 to 50 percent. On a large scale the cacao beans are roasted, ground, and the fat expressed while still hot by hydraulic pressure. In order to remove the free acid which it contains the carbonates of the alkalies are mixed with the material after grinding and before extraction. In these cases the expressed fat naturally does not contain any free acid, though the soaps which are formed by this process are apt to contaminate the expressed fat.
Adulterations.--By reason of its high price cacao butter is often adulterated by the addition of various fats usually of a vegetable character. Those most generally employed are the stearin derived from the coconut fat and the palm-nut fat. The addition of ordinary edible vegetable oils is easily detected by the usual chemical tests and is especially recognized by the increase in the percentage of iodin absorbed. They also reduce the melting point of cacao butter, and for this reason these oils, with the exception of coconut, are not used very extensively as adulterants. Beeswax and paraffine wax are also used to some extent as adulterants, and when used in connection with vegetable oils they serve to keep the melting point from going too low. Tallow has also been used quite extensively as an adulterant. The detection of these adulterants is so difficult as to be accomplished only by a skilled chemist.
Composition.--Cacao butter is composed chiefly of stearin and palmitin, though other fats and oils are present in small quantities. Although it is generally supposed that cacao butter does not tend to become rancid, this is a mistake, since, when exposed to the conditions which favor rancidity, the fermentation which produces this condition takes place in the butter, though somewhat more slowly and more incompletely than in many other fats. The specific gravity of cacao butter at 50 degrees C. is .892. It absorbs about 35 percent of its weight of iodin. It has a much lower melting point than palm fats and even lower than butter. Its melting point varies from 30 to 33 degrees C. Cacao butter has some of the properties of ordinary butter and has been recommended as a substitute therefor, but it is not likely that it will ever come into common use both because it is less desirable than butter and also because of its high price.
Properties.--Cacao butter has a light amber tint and tends to become bleached on long standing. It has a very pleasant flavor, reminding one of the flavor of the preparations of chocolate. At ordinary temperature, 70 degrees F., it is quite solid and sometimes even brittle.
=Coconut Oil or Butter.=--This is a very abundant natural fat and is obtained from the kernel of the coconut, especially the two species Cocos nucifera L. and Cocos butyracea L. At ordinary temperature coconut oil is of the consistency of fat. Its taste is pleasant, and it possesses an odor which is not disagreeable or undesirable. It differs from cacao butter in the ease with which it becomes rancid, at which time it takes on a very disagreeable flavor and taste. The coconut oil of commerce is distinguished by different names, according to the country in which it is made.
Cochin oil is a variety which is regarded as of the finest quality, being almost colorless, and is prepared in Malabar.
Ceylon oil is another very important variety made in the neighborhood of and imported from Ceylon. It is regarded as of somewhat inferior variety to Cochin oil, due probably to less care taken in the cultivation of the plant and the preparation of the oil.
Another variety of coconut oil is known as copra oil. The term “copra” is applied to the sun-dried or kiln-dried kernel of the coconut. In this dried state the fruit can be shipped in bulk and large quantities of it can be sent to Europe or other countries, where the oil is either obtained by extraction or by compression in a hydraulic press. This is regarded as of the least desirable quality.
Coconut oil resembles palm-nut oil in its chemical composition, with the exception of the relative proportion of palmitic acid. The specific gravity of coconut oil or fat at 40 degrees C. is about .912 and reduced to 15 degrees C. about .925. Coconut oil absorbs very little iodin, which is one of its principal characteristic chemical properties. The quantity of iodin absorbed may be taken as about eight percent of the weight of the oil. Coconut oil is one of the vegetable fats which resembles butter to some extent in the high content of volatile acid which it contains. If, under given conditions, butter may be regarded as having a volatile acid number of 27, coconut oil will have upon the same scale a volatile acid number of about 7, whereas ordinary vegetable oils and fats will have less than 0.5 on a similar scale. Coconut oil may be regarded as the one edible oil which approximates in constitution ordinary butter. Coconut oil has been used very extensively as an adulterant for oleomargarine, since by reason of its high volatile acid it brings that substance much nearer to the composition of butter or indicates a larger percentage of butter therein than is actually present. While it is used extensively as human food its principal value is for soap making. It appears as an edible fat under various names, such as “vegetable butter,” “lactine,” “nucoline,” “palmin,” etc. Coconut oil is also very extensively used in the manufacture of candies and confections.
Adulterations.--Coconut oil is rarely adulterated. About the only adulteration of any consequence is that of the admixture with palm-kernel oil, which has properties very much like that of coconut oil. These two oils are ordinarily about the same price and therefore there is no inducement to practice adulteration.
=Palm Oil or Fat.=--This oil is obtained from the fleshy part of the fruit of the palm tree Elæis Guineensis Jacq. and Elæis melanococca Gaertn. Extensive groves of these trees are found in Africa and also in the Philippines. In Africa they grow particularly upon the western coast. There is a large number of varieties of palm trees that afford this fat, but the two mentioned are the principal ones. This fat becomes solid at about the temperature of the body. It has a somewhat higher melting point than butter, which becomes liquid at a temperature of from 34 to 36 degrees C. When once solid the fat may be heated to 41 or 42 degrees before it again becomes liquid. Palm oil has rather a pleasant taste and is regarded as an edible fat of high quality, and is largely used as such by Europeans and in Africa and other countries where the fat is produced. The fat also has a very pleasant odor which is said to resemble somewhat that of violets. This pleasant odor is quite persistent and remains even in the fatty acids after they have been converted into soap. Palm oil is manufactured in the crudest possible way by the natives, and immense quantities are lost for this reason. By reason of this crude method, which leaves the oil in contact with the putrescible matter, palm oil often comes into the market in a rancid state or at least with a high content of free fatty acid. Appreciable quantities of water are also found in the crude article.
Inasmuch as the natural color of palm oil is somewhat too deep for the taste of the ordinary consumer, ranging from yellow to a dirty red color, it is often bleached in the refining process before being sent into commerce. Ordinary exposure to the air tends to bleach this oil, due probably to the bleaching properties which the air sometimes possesses. Ozone is also employed as a bleaching agent. The bichromate process of bleaching palm oil is very commonly practiced. By this method the oil is freed from its principal impurities and treated with from one to three percent of potassium bichromate and with hydrochloric acid which decomposes the “chrome” liquor, and in the chemical process which attends this reaction decided bleaching effects are produced. The bleaching agents are withdrawn and the oil thoroughly washed with water until all traces of chromate and mineral acid are removed.
Adulterations.--On account of its great cheapness and the fact that the admixture of other oils of lower melting point would detract from its value, palm oil has not been subjected to any extensive adulteration. The most common adulterations are the impurities which are left in the oil in the slovenly method of manufacture employed by the natives of Africa.
Constituents.--As would be expected from the name, one of the chief constituents of palm oil is palmitin. If palm oil is saponified and the solid separated from the liquid fatty acid, the former is found to consist almost exclusively of palmitic acid. The specific gravity of palm oil is taken at a high temperature, as much as 50 degrees C. or above. The specific gravity at this temperature is about .893. Palm oil absorbs a little over one half its weight of iodin. The average iodin number may be regarded as varying from 53 to 55. Aside from the limited use of palm oil for human food it is used chiefly in the manufacture of soap and of candles. It is also used extensively in the tin plate industry to spread over the hot iron surface to preserve it from oxidation until it is dipped into the bath of melted tin.
NUTS.
=The Acorn.=--Many varieties of acorns are used for human food. All of the nuts of the oak family are edible, but some of the larger and more common varieties contain such a quantity of tannin as to be rather bitter to the taste. The wild acorns were formerly utilized very extensively for the fattening of swine, producing an article of pork of high palatable value but with the production of a fat of a low melting point, unsuitable for the manufacture of lard for summer use. The term applied to the natural nuts eaten by swine for this purpose is “mast,” and formerly “mast-fed” pork was an extensive article of commerce. The disappearance of the oak and beech forests, however, have practically eliminated this variety of pork from the markets, at least to any extent which can be called commercial.
Composition of the Acorn.--Edible portion, 64.4; refuse, 35.6.
EDIBLE PORTION. Water, 4.1 percent Protein, 8.1 „ Fat, 37.4 „ Starch and sugar, 48.0 „ Ash, 2.4 „ Calories per pound, 2,718
The acorn resembles the chestnut in its composition, containing more carbohydrates than fat. It is therefore not an oily seed, but one of a farinaceous character.
=Almonds.=--There are two species of almond trees, the Amygdalus communis, which is the common or sweet almond, and the Amygdalus amara, or the bitter almond which flourishes very extensively in the south of Europe. California has a climate which, with artificial irrigation, is favorable to the growth of the almond, and practically all that are produced in the United States for commercial purposes grow in that state. It is also cultivated extensively in France, Italy, and Spain, large supplies of the almonds of commerce coming from those localities. The almond is delicious when eaten in the green state, that is when the seed is fully formed but before the hull is hardened. It is rarely eaten in this condition in the United States, but forms a common article of diet upon the table of the Europeans in the early summer.
Composition of the Almond.--
-------------------+-------+--------+------+---------+------ | | | | TOTAL | | | | | CARBO- | |WATER. |PROTEIN.|FAT. |HYDRATES.| ASH. -------------------+-------+--------+------+---------+------ | _Per- | _Per- |_Per- | _Per- |_Per- Edible portion: | cent.| cent.|cent.| cent. |cent._ California almonds,| 4.8 | 21.0 |54.9 | 17.3 |2.0 European almonds, | 6.0 | 23.5 |53.0 | 14.4 |3.1 -------------------+-------+--------+------+---------+------
In the United States the almond is eaten very extensively, often roasted and salted. In this condition it is found as a relish in many menus. The roasting improves to a certain extent the flavor of the nut, but the quantity of salt which is used is not always beneficial, inasmuch as an abundance of salt is eaten with other portions of the food. One of the most valued varieties is the Jordan almond, illustrated in the accompanying colored plate.
=Beechnuts.=--The beech tree is a very common forest tree throughout the northern part of the United States. Formerly immense areas in southern Ohio and Indiana were covered almost exclusively by the beech tree (Fagus americana Sweet). The beechnut is triangular in shape, resembling buckwheat, and formerly was produced in immense quantities over the region mentioned above. In the early days it was the principal food for swine. The hogs which are fattened by eating the beechnut and acorn produce a species of pork of a peculiar and very highly prized flavor. The celebrated hams and bacons of the southern Appalachian ranges were produced from the variety of hogs known as razor-backs fattened on mast, namely, the chestnut, beechnut, and acorn. The beechnut is also one of the principal winter foods of the squirrel and other animals which store their food for winter use. In the cutting of the forests in the winter often large stores of beechnuts are found stored away by squirrels and birds. The beechnut is not very abundant upon the markets of the country, but is eaten very largely by those who live in the vicinity of beech woods.
Composition of the Beechnut.--
-------------------+-------+------+------+------+-------+------+------ | | | | | TOTAL | | | | | | | CARBO-| | | | | PRO- | | HY- | | CALO- |REFUSE.|WATER.| TEIN.| FAT. |DRATES.| ASH. | RIES. -------------------+-------+------+------+------+-------+------+------ | _Per- |_Per- |_Per- |_Per- | _Per- |_Per- |_Per Fagus Americana: | cent.|cent.|cent.|cent.| cent.|cent.|pound_ Edible portion, | .... | 4.0 | 21.9 | 57.4 | 12.2 | 3.5 | 3,263 As purchased, | 40.8 | 2.3 | 13.0 | 34.0 | 7.8 | 2.1 | 1,932 Fagus sylvestris:| | | | | | | Edible portion, | .... | 9.1 | 21.7 | 42.4 | 22.9 | 3.9 | .... As purchased, | 33.0 | 6.1 | 14.5 | 28.4 | 15.4 | 2.6 | .... -------------------+-------+------+------+------+-------+------+------
=Brazil-nut= (Bertholletia excelsa Humb. and Bonpl.).--Large quantities of this nut are imported into the United States from Brazil and form an important article of food in many localities. This nut is not grown in the United States. It is also known as cream nut. The nut is triangular in shape and has a dark brown rough exterior. The kernel is highly flavored and quite oily. The tree is so sensitive to the cold that it will not grow successfully even in southern Florida, although many attempts have been made to introduce it into that locality.
Composition of the Brazil-nut.--Edible portion, 50.4; refuse, 49.6.
---------------+-------+------+------+------+-------+------+------ | | | | | TOTAL | | | | | | | CARBO-| | | | | PRO- | | HY- | | CALO- |REFUSE.|WATER.| TEIN.| FAT. |DRATES.| ASH. | RIES. ---------------+-------+------+------+------+-------+------+------ | _Per- |_Per- |_Per- |_Per- | _Per- |_Per- |_Per | cent.|cent.|cent.|cent.| cent.|cent.|pound_ Edible portion,| .... | 5.3 | 17.0 | 66.8 | 7.0 | 3.9 | 3,329 As purchased, | 49.6 | 2.7 | 8.6 | 33.6 | 3.5 | 2.0 | 1,678 ---------------+-------+------+------+------+-------+------+------
=Butternut= (Juglans cinerea L.).--The butternut is another variety of walnut which grows very extensively in the United States and has the same geographical distribution as the walnut, except that the butternut is not so common west of the Mississippi. The tree does not grow so large as the walnut tree, nor is its wood so highly valued for commercial purposes. While the walnut is a round nut the butternut is very much elongated, forming an oval-shaped nut which is very highly valued as a food. The coloring matter of the butternut is practically the same as that of the walnut. The butternut also has a fleshy outer covering not so thick as that of the walnut and which is removed in the same way in the harvesting.
Composition of the Dry Butternut.--
EDIBLE PORTION. AS PURCHASED. Refuse, .... 86.4 percent Water, 4.4 percent .6 „ Protein, 27.9 „ 3.8 „ Fat, 61.2 „ 8.3 „ Sugar, etc., 3.5 „ .5 „
=The Chestnut= (Castanea dentata (Marsh.) Bork).--The chestnut tree grows in great abundance wild in the United States, especially in the eastern portion on the foothills of the Alleghanies. In some localities it originally formed vast forests. The value of the timber and the fact that the chestnut grows only on good soil were prominent factors in the destruction of many of the original forests, especially those covering the arable lands. The trees still grow in great abundance, especially in the hilly regions.
In France the chestnut is very widely grown, and the nut is used very extensively as food by the poor classes. The nuts are often dried and ground to a flour which is mixed with water and baked in thin sheets, forming a very heavy but a sweet and nutritious cake. The chestnut is used in the preparation of many dishes, prized even by those in easy circumstances. In Italy the chestnut is also widely cultivated, and the nut is ground to form a kind of porridge known as polenta which is very extensively used as food. In the Apennines a cake made of chestnut flour and baked on hot stones is used under the name of necci. In Corea the chestnut is said to be a very extensive article of food, taking the place of the potato. It is eaten raw, boiled, roasted, or cooked with meats. The chestnut differs from the oily nuts in the smaller proportion of fat and the very much larger proportion of sugar and starch,--in fact, starch is almost missing in some of the oily nuts, the carbohydrates present in the very oily being chiefly sugars. In the chestnut the starch is more abundant than the sugar, and for this reason the chestnut meal is more like the meal of the ordinary cereal than that of the oily seeds. The chestnut, also, as it is gathered fresh contains a great deal more water than the ordinary fresh seeds, the quantity ranging from 40 to 50 percent.
The average composition of the fresh chestnut, edible portion, is represented by the following data:
Water, 42.7 percent Protein, 6.5 „ Fat, 6.3 „ Starch and sugar, 43.1 „ Ash, 1.4 „
The dried chestnuts, that is, those which have been kept for several months or which have been artificially dried, have a composition represented by the following data:
Water, 4.8 percent Protein, 11.6 „ Fat, 15.3 „ Sugar and starch, 65.7 „ Ash, 2.6 „
The average weight of the hull of the chestnut is 15.9 percent of the total weight of the fresh nut, and 23.4 percent of the average weight of the dried nut. The above data are confirmatory of the statement that the meal of the chestnut in its composition is very much like that of the oily cereals, for instance, of Indian corn meal or oats. It, however, contains more oil and less protein than the cereals referred to. It is readily seen from the above data that chestnut meal may not properly take the place of Indian corn as human food. The nut of the chestnut tree ripens at the time of frost.
The wild chestnut shrub, which springs up in great numbers where the original trees are cut away, is now extensively grafted with cultivated varieties. In Pennsylvania there are large orchards of the Paragon chestnut which have been grown in this manner.
=Chinese Nut= (Nephelium litchi Cambess.).--This is not a true nut in the ordinary sense of the word, but is usually classed with nuts. It is a product of China and is imported into the United States for consumption by our Chinese population. In the fresh state in China it has the reputation of being one of the best fruit products of that country, having flesh of a white color and a flavor resembling that of high-grade grapes. 41.6 percent of the fresh nut is refuse matter. The edible portion has the following composition:
Water, 17.9 percent Protein, 2.9 „ Fat, .2 „ Starch and sugar, 77.5 „ Ash, 1.5 „ Calories per pound, 1,453
The above data show that in chemical composition the Chinese nut does not belong to the class of nuts at all. It is a fruit, its nutritive material being almost exclusively carbohydrates, while in the true nut the principal nutritive substances are the protein and the oil.
=Coconut.=--The coconuts which are consumed in the United States are mostly imported. It is estimated that three hundred thousand coconut trees (Cocos nucifera L.) have been planted in Florida, and from 15 to 20 percent of them are already bearing. The common name of the tree is the coconut palm. The fruit of the coconut palm is used for many purposes. The immature nuts are often used medicinally, forming the base of a valuable ointment for external use. The jelly which lines the shell of the more mature nut furnishes a food product of great delicacy and high nutritive value. The milk of the coconut is itself highly esteemed as a delicious article of food. Grated coconut is one of the basic constituents of that familiar condimental substance, East Indian curry. Coconut oil is a very highly edible fat from which butter is made. The fat itself is valuable for cooking purposes. The composition of the coconut is shown in the following table:
---------------+-------+------+------+------+-------+------+------ | | | | | TOTAL | | | | | | |CARBO- | | | | | PRO- | | HY- | | CALO- |REFUSE.|WATER.| TEIN.| FAT. |DRATES.| ASH. | RIES. ---------------+-------+------+------+------+-------+------+------ | _Per- |_Per- |_Per- |_Per- | _Per- |_Per- |_Per | cent.|cent.|cent.|cent.| cent.|cent.|pound_ Edible portion,| .... | 14.1 | 5.7 | 50.6 | 27.9 | 1.7 | 2,986 As purchased, | 48.8 | 7.2 | 2.9 | 25.9 | 14.3 | .9 | 1,529 ---------------+-------+------+------+------+-------+------+------
The solid edible portion of the nut is highly oleaginous and contains also a considerable quantity of starch and sugar. Coconut milk is much poorer in nutrients than cow’s milk, containing over 92 percent of water, only .4 percent of protein, and only 1.5 percent of fat. The carbohydrates contained therein are chiefly sugars.
=Filberts.=--The term filbert, according to some etymologists, is a corruption of the term “full beard,” and is so named on account of its having many long beards or husks. The filbert is the fruit of the cultivated hazel tree (Corylus avellana L.). The nut contains a kernel having a pleasant taste and is quite oily and nutritious. It is not cultivated to any extent in this country where we rely principally upon the wild hazel for the hazelnut. The composition of the filbert is shown in the following table (edible portion, 47.9; refuse, 52.1):
EDIBLE PORTION. Water, 3.7 percent Protein, 15.6 „ Fat, 65.3 „ Sugar and starch, 13.0 „ Ash, 2.4 „ Calories per pound, 3,432
The filbert is produced in large quantities on the Asiatic shore of the Black Sea. The region of Trebizond is the most prolific source of the filbert.
=Hazelnut.=--The hazelnut grows on a small tree or large shrub (Corylus avellana L.). The species which grows wild in the United States is known chiefly as Corylus america Walt. It is from this shrub that the common wild hazelnut is obtained. There is also another variety grown in this country, Corylus rostrata Ait. The hazelnut is a small, nutritious, and palatable nut of a brown color and grows over a very large area of the United States, especially in the northern part of the country. It is quite an article of commerce, but is not cultivated to any great extent. The cultivated variety, as has already been stated, is known as the filbert.
Composition of the Hazelnut.--
---------------+-------+------+------+------+-------+------+------ | | | | | TOTAL | | | | | | |CARBO- | | | | | PRO- | | HY- | | CALO- |REFUSE.|WATER.| TEIN.| FAT. |DRATES.| ASH. | RIES. ---------------+-------+------+------+------+-------+------+------ | _Per- |_Per- |_Per- |_Per- | _Per- |_Per- |_Per | cent.|cent.|cent.|cent.| cent.|cent.|pound_ Edible portion,| .... | 3.7 | 15.6 | 65.3 | 13.0 | 2.4 | 3,432 As purchased, | 52.1 | 1.8 | 7.5 | 31.3 | 6.2 | 1.1 | 1,644 ---------------+-------+------+------+------+-------+------+------
=Hickory-nut.=--The hickory-nut is another one of the nuts which sometimes is classed with walnuts and grows very extensively wild throughout the United States, having the same geological distribution as the walnut and butternut. The hickory tree (Hicoria ovata (Mill.) Britton) produces a nut of highest quality. On account of the character of the bark, which becomes detached and often widely separated from the trunk, it is known as the shagbark or shellbark hickory.
Another variety of the hickory tree is known as the pignut (Carya glabra). The nut produced by this tree is much less prized than the other hickories, often containing a sufficient amount of tannin to make it distinctly bitter. The wood of the hickory is very tough and elastic and is used extensively in the manufacture of spokes for wagon-wheels, axe-handles, etc. The young hickory trees grow thickly together and have a slender reed-like growth. They are used extensively in the manufacture of hoop-poles. The hickory has suffered from the advance of the farmer much in the same manner as the walnut and other valuable timber trees. The original trees have almost entirely disappeared. The young trees grow vigorously and in a few years will bear nuts, and in some localities the care and cultivation of the wild tree has been established for the purpose of securing new forests of nut-bearing trees. The hickory-nut is even more highly prized for eating purposes than the butternut and walnut, but should be eaten under the same conditions, namely, before the passing of the first winter after their production. They, also, on account of their high content of oil, tend to become rancid when they are kept through the warm summer.
Composition of the Dry Hickory-nut.--Edible portion, 37.8; refuse, 62.2.
EDIBLE PORTION. Water, 3.7 percent Protein, 15.4 „ Fat, 67.4 „ Sugar and starch, 11.4 „ Ash, 2.1 „ Calories per pound, 3,495
=Peanuts.=--The peanut is a widely cultivated plant. It grows extensively in the United States, and is especially regarded as a crop of high value in North Carolina and Virginia. Very large quantities of peanuts are grown in Senegal, in Algiers, in Egypt, and in many other localities.
The pod containing the seed grows underground, but is not a part of the roots, properly so-called. The pods are attached by slender stems to the stalk of the peanut. The pod of the peanut matures underground, and it may, therefore, be regarded as the seed of the plant, entering and maturing underground. The seeds are immediately covered by a soft envelope and then by several similar coverings. For edible purposes they are much improved by roasting, which gives them an aromatic, nutty flavor which is much admired. A striking illustration of the peanut is shown in the accompanying colored plate.
Peanuts are used as food both directly, as after roasting, and indirectly, by the expression of oil, which after proper refining is considered of high value for edible purposes. The oil of the peanut forms an edible oil of rich flavor, pleasant taste, and high nutritive value. It is used, either alone or mixed with other edible oils, notably with olive oil for table purposes and for the making of salad dressing. The residue of the pressings for peanut oil are highly valued as a cattle food, containing large quantities of nitrogenous nutriment, and also as a manure.
The composition of the peanut varies greatly in different localities. Its chief value as a food material lies in the high percentage of protein it contains and the high percentage of fat. The composition of the typical hulled peanut is shown in the following table:
Water, 9.2 percent Protein, 25.8 „ Fat or oil, 38.6 „ Sugar, starch, etc., 24.4 „ Insoluble cellulose, 2.5 „ Ash, 0.9 „
Only the blossoms which form on the lower part of the stalk produce the fruit, since it is necessary that the long stem should strike the earth and the young fruit penetrate to the depth of from five to six centimeters in order that the fruit may mature. This method of penetrating the earth is shown very well in the colored figure already mentioned.
The original home of the peanut is not definitely known, but is supposed to be Africa. It was first described as occurring on the American continent by Ferdinand de Oviedo in San Domingo in the beginning of the 16th century. It is now very generally distributed in all the tropical countries in South America, Asia, and Africa, and, as before described, grows very well as far north as the northern boundary of North Carolina and in southern Virginia. Peanuts are used for food in all the countries mentioned with previous preparation and roasting.
The above data show that the peanut is a food product extremely rich in oil and protein and comparatively poor in carbohydrates. For dietetic purposes it should be eaten with some highly amylaceous substance, such as potato, rice, or tapioca.
The value of the peanut for food purposes is not fully realized in this country, where it is eaten rather as a relish and as an incident to the circus or the picnic. In such cases they are usually consumed in too large quantities and by unbalancing the ration may produce unpleasant effects from which an unreasonable prejudice against this valuable food product might arise.
=Peanut Butter.=--An oily preparation of the peanut or the oil therefrom deprived of a part of its stearin is known as peanut butter and is used as a substitute for ordinary butter. What has been said of the nutritive value of the oil of the peanut applies also to this product. The butter has the peculiar flavor of the peanut which is not agreeable to all persons, though, perhaps, this fact does not materially interfere with the nutritive value of the product. The nuts are also powdered more or less finely and mixed with other food products. Peanuts which grow in northern Senegambia are regarded very highly for the manufacture of fine salad oil, and peanut oil is used extensively for this purpose.
=Peanut Butter and Peanolia.=--Peanut butter and peanolia are used to a considerable extent in the United States as food products. They are prepared from peanuts, properly roasted, ground to a fine powder, and mixed with an appropriate quantity of salt. The analyses of the samples of these products, made in the Connecticut Agricultural Experiment Station, show the following composition:
PEANUT BUTTER. PEANOLIA. Water, 2.10 1.98 Protein, 28.66 29.94 Fat, 46.41 46.68 Sugar and dextrin, 6.13 5.63 Starch, 6.15 5.58 Insoluble cellulose, 2.30 2.10 Common salt, 3.23 4.95 Ash, .80 1.08
The above analyses show that the preparations are produced from the roasted peanuts, which process reduces the water to about 2 percent. The ground, roasted product is mixed with about 4 percent of common salt. The other constituents are the same as those of the peanuts from which the preparations were made. Of the carbohydrate content of the peanut about 4 percent has been found to be pentosans.
=Where Peanuts are Grown.=--Virginia is one of the most important of the peanut-growing states, especially in its southeastern portion. The Commissioner of Agriculture of Virginia reports that about one hundred thousand acres are planted annually in the state of Virginia, producing over four million bushels. Fifty bushels per acre is considered a good average yield. An important point in the production of good peanuts is the selection of the seeds. The most vigorous and well formed kernels are to be selected for planting, and especially those that are produced by plants of identical size and shape. By a selection of this kind the quality of the crop can be greatly improved.
One of the peculiarities of the peanut is that it is an underground legume. All other leguminous fruits mature above the soil. Its underground habitat is the reason for its botanical name, hypogæa. If the stem carrying the small, yellow, butterfly-shaped flowers and which springs from the axis of the branch above the ground fails to reach the soil no fruit is formed. If the soil is properly cultivated the germ may penetrate of its own accord. However, art assists nature in this matter and covers up the pods so as to give them a better start. The peanut, like some other leguminous crops, develops nodules upon its roots in which the bacteria that assimilate free nitrogen live in symbiotic union with the plant itself.
=Pecan-nut= (Hicoria pecan (Marsh.) Britton; Carya olivæformis Nuttall).--The pecan is a nut which is very much valued and grows, with a most excellent flavor, in the southern part of the United States. Texas, Louisiana, southern Alabama, Mississippi, Georgia, and Florida are the principal regions where the pecan grows, although it is cultivated in some instances much further north.
The pecan belongs to the same family as the hickory-nut and is indigenous to the United States. It grows wild over a large area, extending from southern Illinois and Indiana to the Gulf. It often forms very large trees in the forests. There are several species of Hicoria. The fruit of the pecan is especially valued on account of the thinness of the shell and its extremely pleasant and aromatic flavor. As is the case with most nuts, it is composed chiefly of oil and proteids, the sugar and starch being in minute proportions. The composition of the fruit of the pecan, when divested of its hard shell, is given in the following table:
EDIBLE PORTION. Water, 2.9 percent Protein, 10.3 „ Fat, 70.8 „ Sugar, starch, etc., 14.3 „ Ash, 1.7 „ Calories per pound, 3,445
For marketing purposes the pecans are now largely grown in orchards, as the supply of the wild nut is uncertain, and its texture and flavor are not so fine as the cultivated variety. The cultivated variety may also be grafted upon the wild tree with good effects. The tree begins to bear at four or five years of age. A comparative appearance of the wild and cultivated nut is shown in the accompanying Fig. 59. The tree, when full grown, is handsome in appearance, and is valued as a shade tree as well as a fruit producer. The full grown tree is shown in the accompanying Figs. 58 and 60.
=Pine-nuts.=--In many portions of the western part of our country pine-nuts are consumed largely as food. There are several species of pines yielding edible nuts on the Pacific coast of the United States and as far east as Colorado and New Mexico. These nuts are articles of considerable importance in the commerce of many of the cities of California. The principal specimens of pine which yield edible nuts are Pinus monophylla Torr. and Frem., Pinus edulis Engelm., Pinus sabiniana Dougl. The refuse is usually less than 50 percent of the total weight of the nut.
Composition of the Edible Portion.--
-----------------+------+--------+----+------+----+-------- | | | |STARCH| |CALORIES | | | | AND | | PER |WATER.|PROTEIN.|FAT.|SUGAR.|ASH.| POUND. -----------------+------+--------+----+------+----+-------- Pinus monophylla,| 3.8 | 6.5 |60.7| 26.2 | 2.8| 3,327 „ edulis, | 3.4 | 14.6 |61.9| 17.3 | 2.8| 3,364 „ sabiniana, | 5.1 | 28.1 |53.7| 8.4 | 4.7| 3,161 -----------------+------+--------+----+------+----+--------
=Pistachio.=--The nut of the pistachio (Pistachia vera) is used very largely for flavoring purposes and also for food. The tree is a native of Syria but has been cultivated in southern Europe for many years. The nut produced in America, though somewhat larger than the native Syrian fruit, has not half so high a palatable value. The pistachio is grown to some extent in the southern part of the United States and also in California. The kernel of the fruit is green in color and has a flavor which in some respects is reminiscent of almonds. It is used chiefly in this country in the manufacture of confectionery and ice creams.
Composition of the Pistachio.--
EDIBLE PORTION. Water, 4.2 percent Protein, 22.3 „ Fat, 54. „ Starch and sugar, 16.3 „ Ash, 3.2 „ Calories per pound, 3,235
=Walnuts= (Juglans nigra L.).--The American walnut grows wild over a very large portion of the country, especially the middle section west of Maryland to the Mississippi river. The walnut tree is especially abundant along the Ohio river, where it forms in the early summer a dense foliage. The trees often attain a very great size, reaching a diameter as great as five feet.
The walnut trees grow only on rich soil, hence, unless the country was very hilly and unsuitable for cultivation, the walnut forests were the first to fall before the axe of the pioneer. Later the demand for walnut lumber completed the devastation of the walnut forests, until now very often in the regions where fifty years ago the trees were extremely abundant a large walnut tree is rarely seen. The walnut lumber has peculiar lasting powers, and on account of its natural color and grain is of the highest value for building and ornamental purposes. The early farmers in the Ohio valley made their rail fences out of walnut trees. The wild nut grows in a dense kernel and is covered with a thick pericarp which is green even at the time when the fruit is ripe. After a frost when the fruit naturally falls from the trees the outer covering disintegrates. When the nuts are gathered by boys the outer covering is usually beaten off with clubs. It contains a coloring matter of a brown or brownish-black tint which the early housewives used for dyeing homespun cloth. The bark of the tree also contains to a greater or less extent the same coloring matter. The kernel of the walnut, that is, the edible portion, is extremely rich in oil and protein and has a very pleasant taste. Like other nuts the walnut is best during its first winter, since on longer keeping the oil tends to become rancid and the fruit unpalatable.
=White Walnut= (Juglans regia L.).--The white walnut, commonly known as the English walnut, is grown very extensively in France. All the departments of south central and southeastern France grow these walnuts as a valued crop. The best walnut orchards are at an altitude of from 600 to 900 feet. Only the outer or exposed limbs produce perfect nuts. In planting the most important precaution is to give the trees plenty of room, 15 yards is about the usual distance at which they are planted. The trees are cultivated and fertilized with manure and commercial fertilizers every two or three years. A bearing orchard of these white walnuts in France is worth from four to five hundred dollars per acre and may yield a revenue of from seventy-five to one hundred dollars a year per acre. The nuts ripen from the middle of September to the end of October. These nuts are used largely in America as a food, for which purpose the kernels are carefully extracted in halves, commonly known as “walnut halves.” In France an excellent table oil is expressed from the dry nut which for many culinary purposes is valued as highly as olive oil. After extraction the oil cake is used for stock food. The white walnut is supposed to have been originally introduced from Persia, though it is commonly known as the English walnut. In the United States the butternut tree is commonly known as the white walnut.
The composition of the kernel of the dry walnut is shown by the following data:
Edible portion:
Water, 2.5 percent Protein, 16.6 „ Fat, 63.4 „ Total carbohydrates, 16.1 „ Ash, 1.4 „
As purchased:
Refuse, 58.1 percent Water, 1.0 „ Protein, 7.0 „ Fat, 26.6 „ Total carbohydrates, 6.7 „ Ash, .6 „
=General Discussion.=--A brief description has been given above of the principal edible nuts used in the United States, accompanied by a statement of their chemical composition. The character of the food products is well shown by the analytical data. Nuts as a whole are extremely oily substances and contain next in importance as a food material, protein. Alone they constitute an unbalanced ration in which the fat and protein are abundantly present at the expense of the starch and sugar. For this reason an exclusively nut diet cannot be recommended, as it surely tends to unbalance the ratio and to disturb the digestion in the great majority of cases. There are doubtless individuals of a peculiar temperament who can thrive on a diet of nuts alone, but such a case is exceptional. On the other hand the value of the nut as a food is undeniable, both as a nutrient and as a pleasant condimental addition to the food. The large percentage of oil in nuts also in many cases is beneficial from the well-known effect of oil in promoting the digestive activities, mechanical and otherwise. Nuts should be eaten in as fresh a state as possible, especially those of a highly oily character. Rancidity not only spoils the taste but interferes largely with their dietetic value. On account of the high amount of oil, nuts are preëminently a heat-forming food and thus can be eaten very freely by those engaged in vigorous bodily exercise and during cold weather. They also form a food especially useful during periods of extreme exertion, since by their combustion they furnish abundant stores of heat and energy.
Many fads relating to foods flourish in various localities. Among them the school of dietetics, which advises a diet solely of nuts, is worthy of mention. It is true that life can be sustained for an indefinite time on a diet of nuts alone. If the nuts are sought in the forests and fields the good effects of the exercise and outdoor life are to be taken into consideration. There is no reason to believe, however, that the general condition of mankind, from a dietetic point of view, would be improved by an exclusive nut diet. The impossibility of supplying man with such a food product is also a factor in the discussion of the problem that should not be forgotten.
VIII. FUNGI AS FOODS
=Mushrooms.=--Certain fungi growing wild or in cultivated soils and having an expanded top on a hooded stem are known as mushrooms. The common form of mushroom (Agaricus campestris L.) grows wild over a large portion of the United States. It is especially abundant in the autumn, growing sometimes during the night after a warm rain, over large areas. When properly cooked it forms a delicious food and condimental substance, highly prized by connoisseurs and others. Belonging to the family of mushrooms, however, are many poisonous varieties which, when eaten inadvertently, often cause serious illness and sometimes death. For this reason mushrooms sold in the open market should be carefully inspected by experts authorized to see that the poisonous varieties are excluded. It not only requires a good botanist, but also one skilled in the practical differentiation of the different varieties by physical appearance rather than by botanical analysis, to properly separate the poisonous from the edible varieties.
Historical.--Mushrooms have been, since historical times, extensively used as human food. In a book written five centuries before the Christian era, Athenée, in his “Banquet of Learned Men,” speaks of the poisoning of a mother and her three children by mushrooms. Hippocrates speaks of a girl who had been poisoned by mushrooms and who was cured by the administration of hot honey and by a hot bath. Theophrastes and Nicandre also speak of mushrooms and the poisoning that occurs therefrom. Both Cicero and Horace make reference to mushrooms. Horace advises that Epicureans should confine themselves to the mushrooms that grow upon meadows and refuse to eat all others on account of the danger from poisoning. Ovid also makes frequent allusions to mushrooms and speaks of the influence of warm rains upon their growth. Tacitus refers to the use of mushrooms for food, and Suétonius, in his “History of the Twelve Cæsars,” relates that the Emperor Claudius was poisoned by a dish of mushrooms. It is, therefore, evident that from the earliest times mushrooms were extensively used and the poisonous properties of some of the varieties understood.
Production of Mushrooms.--As has already been mentioned, mushrooms grow wild over a large area of the United States. They are also cultivated very extensively, though not so extensively here as in European countries. The best place for growing cultivated mushrooms is one where the light is excluded or diffused and where the temperature remains reasonably constant. Cellars, caves, and the artificial caverns made by quarrying are peculiarly well suited for the growth of different varieties of fungi, such as mushrooms.
The art of growing mushrooms is not easily acquired. The directions given by the best authorities may be rigidly followed and failure ensue. The skill of the grower appears to be born, not made, and those who have acquired the art succeed where theoretical knowledge fails. For cultural purposes, the Agaricus campestris is most universally employed.
Soil.--The soil best suited for the growth of mushrooms is one rich in decayed or decaying vegetable matter. Mushrooms are often found growing in localities where a log or stump has decayed or where the inorganic matter from the manure of cattle or horses has been distributed on the soil. Artificial beds for the growth of mushrooms are made up largely of organic manurial substances.
Spores.--Mushrooms are grown from spores. The mushroom produces a brown powdery material which consists of almost innumerable simple cells of ovate shape to which the term “spore” has been applied. A spore is not in the strict sense of the word a seed, but simply a cell which by proliferation produces the new fungus. Generally growers do not use these spores directly in seeding mushroom beds. Each complete spore, however, is, under favorable conditions, capable of proliferation or germination, producing a thread-like growth of a spider-web character which penetrates through the soil, prepared and manured, upon which a spore is germinated. This spider-web-like growth, in the common language of mushroom growers, is called the spawn, more properly called the mycelium of the mushroom. When the conditions are favorable, there are formed on the threads of this mycelium small nodules, which are the earlier stages of the complete fungus itself. From the beginning of this growth until the final production of the mushroom two or three days or even a week may elapse. The earlier periods of this growth take place under ordinary circumstances, but the advent of a warm rain or other extremely favorable conditions causes the budding mushroom to grow at an enormously rapid rate. The mushroom may not be said to have a root, stem, and leaf, as is the case with an ordinary green plant, but is practically a single organism, assuming different shapes which are represented by the different varieties and species of growth.
Differing Varieties of Edible Mushrooms.--There is a very large variety of edible mushrooms differing in form, size, and shape from the Agaricus campestris. In the Washington markets there are four principal kinds of mushrooms which are found growing wild in the vicinity of the city. These comprise the common mushroom--Agaricus campestris, the horse mushroom--Agaricus arvensis, shaggy mushroom--Coprinus comatus, and the puff-ball--Lycoperdon cyathiforme.
Conditions of Growth.--The proper shed or cellars having been selected, the first thing to do is to see that the temperature is favorable to the growth of the fungi. Temperatures above 60 degrees F., or below 50 degrees F., are not favorable to the growth. The best temperatures are from 55 to 58 degrees. The locality where the mushrooms are grown should be kept very damp and the air highly saturated with aqueous vapor. The reason that mushrooms grow best in covered places, such as has been mentioned, is due to the particularly favorable influence which the even temperature mentioned and a practically saturated atmosphere have upon the growth. In localities where the changes of temperature are not very severe, mushrooms grow very well in the open. In the county of Kent, England, I have seen mushrooms growing in the open garden, where, by covering with straw, they flourish during the greater part of the year. In the winter time the temperature may be kept quite even by the covering to make abundant crops, while in the months of August, September, and October they grow in the open in great abundance.
Preparation of Seed Bed.--The seed bed for the growth of mushrooms, as has already been indicated, is made principally of well decayed stable or stall manure. The manure must be well fermented, thoroughly disintegrated, and exposed for a sufficient length of time to be in the proper condition. Mushrooms cannot be obtained until the heat attending the fermentation of manure has entirely disappeared.
Directions for growing mushrooms cannot be given here, but those who are intending to enter the business should consult the best authorities and begin in a small way until they acquire the necessary skill before commercial success can be obtained.
Growth of Mushrooms in France.--Perhaps in no country has the cultivation of mushrooms been carried to such a large extent as in France. The principal industries in France are confined to those regions where artificial caves have been made by the quarrying of building stone. The most extensive caverns of this kind exist in the neighborhood of Paris, near Bordeaux, and particularly in the neighborhood of Sceaux. These artificial caverns are often miles in extent and furnish exceptionally favorable opportunities for the growth of mushrooms. The soils or manures on which they are grown must be carried into these caverns, and experience has shown that mushrooms do not continue to grow well in the same locality, and, therefore, the place of growth must be moved from time to time to different parts of the caves. The galleries of these abandoned quarries are sometimes of enormous extent and are from 30 to 150 feet below the surface. They are generally from seven to ten feet high, but occasionally so low that a man cannot stand upright in them. In general they are wide enough for two rows of beds with a foot way 18 inches wide in the center. Where a mushroom bed has been well prepared and properly seeded, it produces about six pounds of mushrooms per square yard. These mushrooms bring, in the market, an average of about 15 cents per pound. It is stated by some authorities that the reason the bed ceases to bear after a time and has to be abandoned or moved is not because of the exhaustion of the food but is due to the ravages of an insect or fly which produces a worm which is fatal to the growth of the fungus. At any rate, it is customary to abandon the beds after they have been bearing for six or eight months and to return to them after a year, when they are found to again be productive.
It is not expected that the general consumer will become an expert in the selection of mushrooms. Where mushrooms are exposed in a public market, it is the duty of the municipal officers in charge of food products to see to it that poisonous varieties are not exposed for sale. It will be of value, however, to the reader to have some idea of the general shape of some of the more common edible and poisonous varieties. It is generally supposed that mushrooms, toadstools, and puff-balls are entirely distinct species and that only the mushroom, so-called, is edible. On the contrary, there are many edible toadstools and many edible puff-balls, and all three classes of fungi belong to the same general family.
Food Value of Mushrooms.--The nutritive value of mushrooms is not exceptionally high, although there is a popular opinion to the contrary. Frequently it has been stated that the mushroom in the vegetable world holds a similar position to beefsteak among meats, being particularly rich in digestible protein. The analytical data which have been collected from numerous sources on the composition of mushrooms do not bear out this popular impression, but, on the contrary, show that the mushroom is a food product consisting very largely of water and of only very small quantities of protein, fat, and carbohydrates.
The composition of some of the common mushrooms is shown in the following table (Farmers’ Bulletin, No. 79, Mushrooms as Food):
---------+------+------+------+------+-----+----+-------+------+---- | | | | NON- | | | | | | | | ALBU-| ALBU-| | | | | | | TOTAL|MINOID|MINOID| | | CARBO-| | | |NITRO-|NITRO-|NITRO-| PRO-| | HY- | | |WATER.| GEN. | GEN. | GEN. |TEIN.|FAT.|DRATES.|FIBER.|ASH. ---------+------+------+------+------+-----+----+-------+------+---- Common | | | | | | | | | mushroom,|91.30 | 0.60 | 0.36 | 0.24 | 3.75|0.20| 3.50 | 0.80 |0.50 Shaggy | | | | | | | | | Coprinus,|92.19 | .45 | .15 | .30 | 2.81| .26| 1.40 | .57 | .98 Inky | | | | | | | | | Coprinus,|92.31 | .36 | .. | .. | 2.25| .24| .... | .72 |1.29 Common | | | | | | | | | Morel, |89.54 | .49 | .37 | .12 | 3.06| .50| 1.60 | .91 |1.08 ---------+------+------+------+------+-----+----+-------+------+----
These data may be compared with the composition of the beefsteak:
Water, 62.5 percent Protein, 19.5 „ Fat, 17.0 „ Ash, 1.0 „
From the above data it is seen that the mushroom does not contain anything like the amount of protein found in beefsteak. It has one-third more water, one-sixth as much protein, and only one-fortieth as much fat. Beefsteak contains no carbohydrates except less than one percent of glycogen, while the amount of carbohydrates in the mushroom varies from 1.5 to 3.5 percent. It is evident that the mushroom is principally valuable as a condimental substance and not as a food product.
Distinction between Poisonous and Edible Varieties.--It has already been stated that only the expert is able to distinguish between the poisonous varieties of mushrooms and those that are edible. Even the skilled botanist, as well as the expert, may sometimes make mistakes in this matter. Hence the only perfectly sure method of protection against the poisonous varieties is the eating of only those which are cultivated and which are known to be free of poisonous properties. On the other hand, the wild variety, by many connoisseurs, is much more highly valued as being more delicate and palatable. It should also be remembered that the cultivation of mushrooms is not very widely extended, and if the supply of the wild variety should be excluded there would be a great diminution of the quantity which is accessible to the consumer. This would be an especial hardship in the United States, where mushrooms grow wild over such wide areas and so abundantly and where the cultivation of them as compared with some other countries is somewhat restricted. There are some general characteristics by means of which a distinction can be made between the edible and the poisonous varieties.
The following rules are given for the rejection of the probably poisonous mushroom by George Francis Atkinson (“Studies of American Fungi--1900”): “In the selection of mushrooms to eat, great caution should be employed by those who are not reasonably familiar with the means of determination of the species, or those who have not an intimate acquaintance with certain forms. Rarely should the beginner be encouraged to eat them upon his own determination. It is best at first to consult someone who knows or to send first specimens away for determination, though in many cases a careful comparison of the plant with the figures and descriptions given in this book will enable a novice to recognize it. In taking up a species for the first time it would be well to experiment cautiously.”
No Certain Rule to Distinguish the Poisonous from the Edible.--“There is no test like the ‘silver-spoon test’ which will enable one to tell the poisonous mushroom from the edible ones. Nor is the presence of the so-called ‘death-cup’ a sure sign that the fungus is poisonous, for Amanita cæsarea has this cup. For the beginner, however, there are certain general rules, which, if carefully followed, will enable him to avoid the poisonous ones, while at the same time necessarily excluding many edible ones.
“1st.--Reject all fungi which have begun to decay, or which are infested with larvæ.
“2d.--Reject all fungi when in the button stage, since the characters are not yet shown which enable one to distinguish the genera and species. Buttons in pasture lands which are at the surface of the ground, and not deep-seated in the soil, would very likely not belong to any of the very poisonous kinds.
“3d.--Reject all fungi which have a cup or sac-like envelope at the base of the stem, or which have a scaly or closely fitting layer at the base of the stem and rather loose warts on the pileus, especially if the gills are white. Amanita cæsarea, however, has a sac-like envelope at the base of the stem and yellow gills as well as a yellow cap, and is edible. Amanita rubescens has remnants of a scaly envelope on the base of the stem and loose warts on the cap, and the flesh, where wounded, becomes reddish. It is edible.
“4th.--Reject all fungi with a milky juice unless the juice is reddish. Several species with copious white milk, sweet or mild to the taste, are edible.
“5th.--Reject very brittle fungi with gills nearly all of equal length where the flesh of the cap is thin, especially those with bright caps.
“6th.--Reject all Boleti in which the flesh changes color where bruised or cut, or those in which the tubes have reddish mouths, also those the taste of which is bitter. Strobilomyces strobilaceus (Scop.) Berk. changes color when cut, and is edible.
“7th.--Reject fungi which have a cobwebby veil or ring when young, and those with slimy caps and clay-colored spores.
“In addition, proceed cautiously in all cases, and make it a point to become very familiar with a few species first, and gradually extend the range of species rather than attempt the first season to eat a large number of different kinds. All puff-balls are edible so long as they are white inside, though some are better than others. All coral-like or club fungi are edible.”
Popular Distinction between Toadstools and Mushrooms.--There is a general opinion that the toadstool is poisonous and the mushroom is not. There is, however, no scientific distinction between the two kinds of fungi, popularly known as toadstools and mushrooms. The distinction is purely an arbitrary one. The small toadstools are often as delicious and as harmless as the small mushroom. The small mushroom, on the other hand, may be as deadly and as undesirable as the worst specimen of toadstool. There is danger especially to two classes of people in the discrimination between the poisonous and edible varieties of mushrooms and toadstools. The first class is composed of those who are practically unaware of the existence of poisonous varieties and the second class of persons are those who claim to be able to tell an edible mushroom from a certain number of tests or claims which they regard as infallible. Both of these classes of persons are apt to be deceived or injured by dangerous varieties.
The following popular signs of distinguishing between the poisonous and non-poisonous varieties are pronounced worthless by Gibson (“Our Edible Toadstools and Mushrooms and How to Distinguish Them”):
“FAVORABLE SIGNS.
1. Pleasant taste and odor.
2. Peeling of the skin of the cap from rim to center.
3. Pink gills, turning brown in older specimens.
4. The stem easily pulled out of the cap and inserted in it like a parasol handle.
5. Solid stems.
6. Must be gathered in the morning.
7. ‘Any fungus having a pleasant taste and odor, being found similarly agreeable after being plainly broiled without the least seasoning is perfectly safe.’
“UNFAVORABLE SIGNS.
8. Boiling with a ‘silver spoon,’ the staining of the silver indicating danger.
9. Change of color in the fraction of the fresh mushroom.
10. Slimy or sticky on the top.
11. Having the stems at their sides.
12. Growing in clusters.
13. Found in dark, damp places.
14. Growing on wood, decayed logs, or stumps.
15. Growing on or near manure.
16. Having bright colors.
17. Containing milky juice.
18. Having the gill plates of even length.
19. Melting into black fluid.
20. Biting the tongue or having a bitter or nauseating taste.
21. Changing color by immersion in salt-water, or upon being dusted with salt.
“These present but a selection of the more prevalent notions. Taken in toto, they would prove entirely safe, as they would practically exclude every species of toadstool or mushroom that grows. But as a rule the village oracle bases his infallibility upon two or three of the above ‘rules,’ and inasmuch as the entire list absolutely omits the only one test by which danger is to be avoided, it is a seven days’ wonder that the grewsome toadstool epitaph is not more frequent.”
The following tests are regarded as favorable by Gibson:
1. Avoid every mushroom having a cup or suggestion of such, at base; the distinctly fatal poisons are thus excluded.
2. Exclude those having an unpleasant odor, a peppery, bitter, or other unpalatable flavor, or tough consistency.
3. Exclude those infested with worms or in advanced age or decay.
4. In testing others which will pass the above probation let the specimen be kept by itself, not in contact with or enclosed in the same basket with other species.
Begin by a mere nibble, the size of a pea, and gentle mastication, being careful to swallow no saliva, and finally expelling all from the mouth. If no noticeable results follow, the next trial, with the interval of a day, with the same quantity may permit of a swallow of a little of the juice, the fragments of the fungus expelled as before. No unpleasantness following for twenty-four hours, the third trial may permit of a similar entire fragment being swallowed, all of these experiments to be made on an empty stomach. If this introduction of the actual substance of the fungus into the stomach is succeeded by no disturbance in twenty-four hours, a larger piece, the size of a hazelnut, may be attempted, and thus the amount gradually increased day by day until the demonstration of edibility, or at least harmlessness, is complete and the species thus admitted into the “safe” list. By following this method with the utmost caution the experimenter can at best suffer but a slight temporary indisposition as the result of his hardihood, in the event of a noxious species having been encountered, and will at least thus have the satisfaction of discovery of an enemy if not a friend.
It may be said that any mushroom, omitting the Amanita, which is pleasant to the taste and otherwise agreeable as to odor and texture when raw, is probably harmless and may safely be thus ventured on with a view of establishing its edibility. A prominent author on our edible mushrooms (McIlvaine) applies this rule to all the Agarics with confidence. “This rule may be established,” he says: “All Agarics--excepting the Amanitæ--mild to the taste when raw, if they commend themselves in other ways, are edible.” This claim is borne out in his experience, with the result that he now numbers over one hundred species among his habitual edible list out of the three hundred which he has actually found by personal test to be edible or harmless. “So numerous are toadstools,” he continues, “and so well does a study of them define their habits and habitats, that the writer never fails upon any day from April to December to find ample supply of healthy, nutritious, delicate toadstools for himself and family.”
“In gathering mushrooms one should be supplied with a sharp knife. The mushrooms should be carefully cut off an inch or so below the cap, or at least sufficiently far above the ground to escape all signs of dirt on the stems. They should then be laid gills upward in their receptacle, and it is well to have a special basket, arranged with one or two removable bottoms or horizontal partitions, which are kept in place by upright props within, thus relieving the lower layers of mushrooms from the weight of those above them. Such a basket is almost indispensable.
“Before preparing mushrooms for the table, the specimens should be carefully scrutinized for a class of fungus specialists which we have not taken into account, and which have probably anticipated us. The mushroom is proverbial for its rapid development, but nature has not allowed it thus to escape the usual penalties of lush vegetation, as witness this swarming, squirming host, minute grubs, which occasionally honey-comb or hollow its entire substance ere it has reached its prime; indeed, in many cases, even before it has fully expanded or even protruded above ground.
“Like the carrion flies, the bees, and wasps, which in early times were believed to be of spontaneous origin--flies being generated from putrefaction, bees from dead bulls, and the martial wasps from defunct “war-horses”--these fungus swarms, which so speedily reduce a fair specimen of a mushroom to a melting loathsome mass, were also supposed to be the natural progeny of the ‘poisonous toadstool.’ But science has solved the riddle of their mysterious omnipresence among the fungi, each particular swarm of grubs being the witness of a former visit of a maternal parent insect, which has sought the budding fungus in its haunts often before it has fully revealed itself to human gaze, and implanted within its substance her hundred or more eggs. To the uneducated eye these larvæ all appear similar, but the specialist in entomology readily distinguishes between them as the young of this or that species of fly, gnat, or beetle.
“As an illustration of the assiduity with which the history of these tiny scavenger insects has been followed by science, I may mention that in the gnat group alone over seven hundred species have been discovered and scientifically described, many of them requiring a powerful magnifier to reveal their identities.
“Specimens of infected or decaying mushrooms preserved within a tightly closed box--and, we would suggest, duly quarantined--will at length reveal the imago forms of the voracious larvæ; generally a swarm of tiny gnats or flies, with an occasional sprinkling of small glossy black beetles, or perhaps a beautiful indigo-blue insect half an inch in length of most nervous habit, and possessed of a long and very active tail. This insect is an example of the curious group of rove-beetles--staphylinus--a family of insect scavengers, many of whose species depend upon the fungi for subsistence.
“Even the large woody growth known as ‘punk’ or ‘touchwood,’ so frequently seen upon decaying trunks, is not spared. A huge specimen in my keeping was literally reduced to dust by a single species of beetle.
“Considering the prevalence of these fungus hosts, it is well in all mushrooms to take the precaution of making a vertical section through stem and cap, excluding such specimens as are conspicuously monopolized, and not being too critical of the rest, for the over-fastidious gourmet will often thus have little to show for his morning walk. I have gathered a hundred specimens of fungi in one stroll, perhaps not a quarter of which, upon careful scrutiny, though fair of exterior would be fit for the table. The fungus hunter par excellence has usually been there before us and left his mark--a mere fine brown streak or tunnel, perhaps winding through the pulp or stem, where his minute fungoid identity is even yet secreted. But we bigger fungus eaters gradually learn to accept him--if not too outrageously promiscuous--as a natural part and parcel of our Hachis aux Champignons, or our simple mushrooms on toast, even as we wink at the similar lively accessories which sophisticate our delectable raisins, prunes, and figs, to say nothing of prime old Rochefort” (pages 33-34).
E. Faupin, the author of the work “Les Champignons Comestibles et Vénéneux,” gives some valuable hints respecting the confusion of edible and poisonous varieties of mushrooms. He also says that the so-called rules which are often formulated to distinguish the good mushrooms from the bad are nearly all misleading. If they are applicable in a few particular cases they surely are not in all, and consequently ought to be judged as of no value. For instance, it has been commonly said that the mushrooms whose flesh changes color when exposed are poisonous. This is true for certain kinds but it is not true for others. There are, indeed, some mushrooms whose flesh undergoes an alteration when it is exposed and which are, nevertheless, of most excellent quality. As an example of this, the variety known as “delicious lactaire” may be cited. On the contrary there are other kinds whose flesh remains white on exposure and which are decidedly poisonous, as for example Amanita citrina Pers. It is also said that a mushroom whose stem is surrounded by a ring is to be considered edible. This indication is altogether deceptive. Some of the most poisonous varieties have well formed rings. It is also misleading to credit the action of the juice of the mushroom in coloring a piece of silver. It is said that those mushrooms whose juice blackens silver are poisonous, while those which do not are harmless. This perhaps is the most dangerous of all the rules to go by, as some of the most poisonous varieties would be admitted on this test. It is also misleading to suppose, as is commonly the case, that mushrooms which are attacked by insects, larvæ, etc., can be eaten without danger. Likewise misleading is the general opinion that mushrooms whose odor is agreeable or which have no appreciable odor are not poisonous. It is high time to eradicate these misleading notions and to let the people know with certainty that aside from the botanical character there does not exist any particular sign nor any particular means of affirming that a given mushroom is edible or poisonous. Science alone, therefore, has the sole power of teaching to distinguish the poisonous from the non-poisonous varieties. For many years attempts have been made to popularize the science which will give to the people the desired information, but in spite of these efforts the number of cases of poisoning does not seem to diminish, and why? The response is evident. It is because the efforts which have been made by mycologists have not yet been appreciated by the mass of people, and because it has not yet been possible to point out to the public at large the poisonous species. The number of species of poisonous mushrooms which are capable of causing death is happily not very great. The Amanitas and the Volvarias are almost exclusively the poisonous species. Let it be understood, therefore, by the people that there do exist mushrooms which are capable of killing. If the people desire to place themselves out of danger let them begin by learning these varieties. Their number is very limited, as there are only five or six species at most. When they are well known it will be very easy to distinguish them and to recognize all others as edible. Following is a list of the most poisonous mushrooms known, and all that are likely at any time to produce death:
Amanita phalloides Fr. Amanita citrina Pers. Amanita verna Bull. Amanita virosa Fr. Volvaria gloiocephala, var. speciosa (Fr.). Amanita muscaria (L.) Pers. Amanita pantherina DC. Lactarius torminosus (Schaeff.) Fr. Lactarius rufus Fr. Lactarius zonarius (Bull.) Fr. Lactarius pyrogalus (Bull.) Fr. Russula emetica Fr. Russula queletii Fr. Russula fœtens (Pers.) Fr. Boletus felleus Bull. Boletus satanus Lenz. Boletus erythropus Cke. Boletus luridus Schaeff. Entoloma lividum Bull.
The Most Poisonous of Mushrooms.--The most poisonous of the common mushrooms is known as Amanita verna Bull. So active is its poison that this variety has become known as the “deadly Amanita.”
=Types of Edible Mushrooms.=--While it is quite impossible for a manual of this kind to give any directions by which a person, not an expert, may make certain distinctions between the edible and poisonous varieties of mushrooms, it is thought advisable to give a fair technical illustration of the two classes. The common mushroom, Agaricus campestris, is shown in the accompanying Fig. 61,--three-fourths its natural size. The second specimen from the left is young and is in a state of development known as a button. The figure at the extreme left is a larger specimen, showing the slightly checked surface that sometimes occurs in this species. In fresh specimens the surface is white, but various shades of light brown, either checked or plain, are often found. The specimen at the right shows the gills on the lower surface of the cap. These gills in a newly expanded mushroom, fresh from the field, are of a beautiful delicate pale pink color, often with a touch of salmon. In the older samples the gills turn to a light brown and finally almost to a black color. This discoloration is chiefly due to the development of almost innumerable spores from which new plants are propagated. If the stem of a common mushroom be broken off and the cap be laid gills downward on a piece of white paper, the spores will drop off and after a few hours will appear as a brown dust. The usual diameter of full-grown specimens of this variety of mushroom is from 1¹⁄₂ to 3 inches, though many smaller and many larger samples are found.
This variety of mushroom is the principal one which is exposed upon the markets of Washington. They are especially abundant in the autumn after copious rains often succeeding the usual period of drought in that region. October is the banner month for this variety of mushroom. The mycelium from which the autumn mushroom grows is formed in the spring, and after the dry period of summer the little spheroid granules formed upon the mycelium are capable of absorbing the moisture of the warm autumnal rains and rapidly expand to the full-grown mushroom. After all the conditions of growth are fulfilled it usually requires only a single night for a button to push through the surface of the soil and expand its cap. Mushrooms are particularly obnoxious to the ravages of insects, and it is always advisable that they should be gathered and eaten immediately after they are formed. The insect larvæ attack the mature mushroom, travelling up through the stem into the cap, and decomposition rapidly follows.
It is easy to determine whether a mushroom is wormy or not by breaking off the stem close to the cap and observing if there are little holes through which the larvæ have passed upward into the cap. The common mushroom occurs most frequently on lawns and in pastures, and especially in neglected fields where weeds have been succeeded by a scant covering of grass. Sometimes during the spring and summer, as well as in the autumn, the common mushroom is found upon the market. These mushrooms usually are produced upon the garbage dumping grounds near the city. The garbage and refuse from the city furnish the manurial conditions required for a speedy development of the mushroom from the mycelium.
The Horse Mushroom (Agaricus arvensis Schaeff.).--This variety of mushroom is also one which grows in great abundance in the neighborhood of Washington and in other latitudes affording a similar environment. This specimen is in many respects like Agaricus campestris but the surface of the cap is somewhat darker colored. The ring on the stem is also wider and thicker than in campestris. This variety also grows larger than campestris, and the diameter of the cap is commonly from three to six inches. The figure is only about one-half the natural size. The horse mushroom is frequently confounded with the common mushroom, and there is practically no difference in their edible qualities. It grows preferably in gardens rather than fields, and especially in gardens which have been heavily fertilized. It also frequently appears in old beds composed of decayed stable manure which has been used for forcing beds for early vegetables.
Shaggy Mushroom (Coprinus comatus Fr.).--The accompanying Fig. 63 represents a group of three specimens of this variety of mushroom growing from a single base. The largest one is already showing signs of liquefaction and decomposition and a part of the cap has already disappeared. One of the peculiarities of this species is that beginning with the edge of the cap the whole mushroom dissolves sometimes within a day, when it is full grown, into an inky-black fluid. A portion of this inky fluid has run partly down the white stem of the largest mushroom. The cap of this mushroom, except when it begins to liquefy, resembles somewhat the form of a partially closed umbrella. In the early stages of growth the cap, gills, and stem are white, except the apex of the cap, which is generally dark-colored. The surface of the cap is covered with delicate lacerated scales, the characteristic from which the name comatus or shaggy is derived. The juice from the fresh sample is colorless as water. When it first begins to turn it is wine-colored, and until the juice is very deeply discolored the sample is still edible. After the juice has turned completely black it is considered too old to be eaten. This species of mushroom grows best in shady places, in a soil well supplied with humus. The season in which this variety of mushroom is most abundant is late in the autumn or early in the winter, when the nights are cold but the ground is not yet frozen. The liquefaction and decay of this mushroom come on so quickly that it is not usually infested with larvæ which do not have time to develop before the mushroom is reduced to a shapeless mass. The most common organism found is the myriapod, a thousand-legged worm, which often finds its way between the gills and stem. This cavity should always be examined for worms of this kind when the mushroom is being prepared for the table.
Fairy Ring Mushroom (Marasmius oreades Fr.).--This variety is one which is interesting both on account of its edible properties and by reason of the circular areas in which it often grows. This illustration is about three-fourths of the natural size. The tendency of this variety to grow in the annual form designated is beautifully shown in the accompanying figure, from a photograph taken on the grounds of the Department of Agriculture. The ring in question is seven feet in diameter and the photograph was taken early in November. The stem in this variety has no ring,--the gills are few and widely separated and the cap as it becomes fully expanded has a peculiar knob-like projection in the center. This gives a characteristic appearance to this variety of mushroom. The cap and stem are colored a pinkish-buff, and the gills have a lighter shade of the same color varying in early growth toward a cream tint. The spores are white and can be observed by placing the cap, as already indicated, on a dark-colored paper, preferably black glazed paper. The fairy ring mushroom is one of the commonest species which grows on the lawns in Washington and vicinity. As many as twenty of these fairy rings have been found on the grounds of the Department of Agriculture in one season. In the earlier days, when superstition was more rife than at present, these rings were supposed to mark the places of the dances of the fairies. Another fanciful cause assigned for the production of the rings was that it was due to the effect of lightning striking the ground and burning the grass in a circle, and thus favoring the growth of fungi. Investigations, however, show that the fairy ring is due to a peculiar way in which the mycelium is produced, which begins at a central point, growing uniformly in all directions a few inches each year. After a while the central portion, being older, begins to die, and thus a small circular band is formed which each year increases in size, growing regularly on the outside and dying as regularly on the inside. The fairy rings are not always complete circles,--they are sometimes broken and often are crescent-shaped. This variety of mushroom is quite permanent, does not tend to decay as rapidly as some, and resists better than most varieties the attacks of insects. They, however, are very small as compared with the other common varieties.
Puff-balls.--A typical mushroom known as the puff-ball is the variety known as Lycoperdon cyathiforme Bosc. The puff-ball is so plain in its form that a description of its appearance is difficult. Usually the outside is colored brown and the covering is more or less irregularly checked, the white color of the interior showing between the darker, elevated areas. When still quite young the flesh is solid, of a milk-white color, and apparently quite dry. After two or three days it becomes soft, has a yellowish tint, develops a watery and later an amber-colored juice as it continues its development through to the later stages. If the mushroom remains ungathered, the interior dries up into a fine brown powder which is projected into the air when pressed by the finger. It is often blown away by the wind. When the fungus reaches this stage of decay it is very commonly known as “the devil’s snuff-box.” Finally the spores and other dust-like bodies are blown away, and there is left only a dry and leathery framework. In the latter stages the puff-ball is not regarded as edible, not because of its being poisonous, but on account of its dry and leathery consistency. In the neighborhood of Washington puff-balls are found commonly in the autumn on lawns and in gardens, and especially on vacant lots where the soil has remained uncultivated and been closely grazed by cattle. The puff-ball also tends to grow in a fairy ring form, and in the circular area in which it grows the grass is likely to be darker in color, showing the existence of a richer soil. It is only while the interior of the puff-ball is still solid and white, with something like the texture of cheese, that it has its highest edible properties.
Cepe (Boletus edulis Bull.).--This variety of mushroom is one of the most highly esteemed, especially in the south of France. It is large and has a very large, half-pear shaped stem. The flesh of this variety of mushroom is white and quite firm in the young mushroom, but becomes softer with age and assumes on the outside a wine tint. It grows, especially in the late summer and through the autumn, wild in the forest. In the extreme south of France it sometimes appears as early as April. (“Nouvel Atlas de Champignons,” Paul Dumée, page 45.) (“The Mushroom Book,” by Nina L. Marshall, page 109.) The cap is usually from four to six inches in diameter and is a gray, brownish-red or tawny-brown in color.
The Fly Amanita (Amanita muscaria (L.) Fr.).--This is one of the very poisonous varieties of mushrooms. In the illustration the fully matured mushroom is shown at one-half its natural size. This is the most common poisonous mushroom which grows in the District of Columbia and other nearby localities. The points especially to be noticed are the bulbous enlargement at the base of the stem, breaking into thick scales above, the very broad drooping ring near the top of the stem, and the corky particles loosely attached to the smooth, glossy upper surface of the cap. The stem, gills, and the spores are white, the corky particles commonly of a buff color, but sometimes varying almost to white. The glossy upper surface of the cap, beneath the corky particles, varies from a brilliant red to orange-yellow, buff, and even white. Commonly in the vicinity of Washington the coloration is orange in the center, shading to yellow toward the margin. Brilliant red ones are rarely seen in this locality, but white ones are not infrequent, especially late in the season. This was the variety of mushroom that lately caused the death of a well known man in Washington. This poisonous variety is one of the largest, handsomest, and most dangerous of mushrooms, and is one whose poisonous character has been most fully studied. It is abundant in the vicinity of Washington in the fall, growing chiefly in the pine woods and, especially, in the localities which have been frequented by hogs. The chief active poisonous principle of the fly amanita is an alkaloid called muscarine, but other poisonous substances whose exact nature has not yet been discovered also occur in the plant.
When this variety of mushroom is reduced to a paste and exposed where it can be eaten by flies the latter are readily poisoned, and hence the common name of “fly amanita.”
=Symptoms of Mushroom Poisoning.=--The symptoms of poisoning from the fly amanita, as deduced from a number of cases, are varied. In some instances they begin only after several hours, but usually in from one-half to one or two hours. Vomiting and diarrhea almost always occur, with a pronounced flow of saliva, suppression of the urine, and various cerebral phenomena, beginning with giddiness, loss of confidence in one’s ability to make ordinary movements, and derangement of vision. This is succeeded by stupor, cold sweats, and a very marked weakening of the heart’s action. In case of rapid recovery the stupor is short and usually marked with mild delirium. In fatal cases the stupor continues from one to two or three days, and death at last ensues from the gradual weakening and final stoppage of the heart’s action.
=Treatment for Poisoning.=--The treatment for poisoning by Amanita muscaria consists primarily in removing the unabsorbed portion of the Amanita from the alimentary canal and in counteracting the effect of the muscarine on the heart. The action of this organ should be fortified at once by the subcutaneous injection, by a physician, of atropin, in doses of from one one-hundredth to one-fiftieth of a grain. The strongest emetics, such as tartarized antimony or apomorphin, should be used, though in case of profound stupor even these may not produce the desired action. Freshly ignited charcoal or two grains of a one percent alkaline solution of permanganate of potash may then be administered in order, in the case of the former substance, to absorb the poison, or in case of the latter, to decompose it. This should be followed by oils and oleaginous purgatives, and the intestines should be cleaned and washed out with an enema of warm water and turpentine.
Experiments on animals poisoned by the fly amanita and with pure muscarine show very clearly that when the heart has nearly ceased to beat it may be stimulated to strong action almost instantly by the use of atropin. Its use as thus demonstrated has been the means of saving numerous lives. We have in this alkaloid an almost perfect physiological antidote for muscarine, and therefore in such cases of poisoning its use should be pushed as heroically as the symptoms of the case will warrant.
The presence of phallin in Amanita muscaria is possible and its effects should be looked for in the red color of the blood serum discharged from the intestines. (Circular 13, Div. of Botany.)
=Removal of the Poisonous Principle.=--In some parts of Europe the fly amanita is soaked in vinegar and then is eaten with impunity. Some of the colored people in Washington and vicinity are acquainted with this method of treatment, and the practice of soaking these fungi in vinegar and then eating them is not unknown, though the majority of colored women in the markets who deal in mushrooms look upon this species with unrestrained horror.
The poisonous variety is denatured as follows: The stem is well scraped, and the gills are removed from the cap and the upper surface peeled off. The mushrooms prepared in this way are boiled in salt and water and afterward steeped in vinegar. They are finally washed in clear water and then cooked in the ordinary manner and eaten without any injurious results. It is not recommended, however, that a mushroom which contains so much deadly poison should be eaten at all, even after a preparation of this kind. Any carelessness in the preparation or any failure to carry out the process completely would result fatally.
=Canned Mushrooms.=--The canning of mushrooms is an industry of large magnitude, especially in France. The young, unexpanded mushrooms in the form of buttons are those which are usually subjected to the canning process. Mushrooms are brought to the factory where they are cleaned and scraped, the stem cut to a proper length, thoroughly washed in several washings of clean water, and taken to a sulfuring furnace where they are exposed to the fumes of burning sulfur for some time. The purpose of this treatment is to bleach the mushroom and make it as white as possible. Decayed or deformed buttons are not included in the cans of highest quality. The prepared mushrooms are then placed in cans, usually of tin, and preserved by subjecting them to a temperature at or above boiling water until thoroughly sterilized.
=Canned Pieces and Stems of Mushrooms.=--The imperfect portions, the pieces which are cut away, and other fragments of the mushroom, resulting from the preparation of the product described above, are treated practically in the same manner for sterilizing purposes and are sold to the trade under various names, the most common of which is Champignons d’Hotel. They also frequently appear under the name of Champignon Choix and other deceptive labels.
=Adulteration of Mushrooms.=--There is no adulteration practiced of fresh mushrooms unless the occasional occurrence of poisonous varieties may be so considered. It is evident, however, that the introduction of poisonous varieties is the result of carelessness or mistake and not for any purpose. Nevertheless a most exacting supervision over the preparation of fresh mushrooms for the market should be required, and any failure to exercise this care may be considered as resulting in adulteration or depreciation of the character of the product.
In canned mushrooms the presence of sulfurous acid may be regarded as an adulterant, and such a substance, believed to be inimical to health, is not necessary in the preparation of the goods. It is quite certain that the public taste would soon adapt itself to an amber- or brown-colored product in canned mushrooms and value it as highly as the buttons which are white. Since the sole purpose of the use of sulfur is for bleaching, the end secured scarcely justifies the means. It is claimed, naturally, that the use of sulfur is also a safeguard in securing a better keeping of the product, but such an adjunct for keeping purposes is only necessary when the sterilization is not complete. It is to be hoped that the day will soon come when mushrooms bleached with sulfurous acid shall no longer be found upon our market. The use of other preservatives than sulfurous acid has at times been practiced, but it is not believed that there are many cans of mushrooms offered upon the market which contain any chemical preservatives whatever save the sulfurous acid above noted. Since the canned mushrooms are valued principally as a condiment, the inclusion of imperfect or partially decayed or malformed buttons is extremely unusual. The buttons are separated into sizes of approximately the same magnitude, so that a can of the product is uniform in size as well as in quality. The customer may be reasonably certain that he is getting a good, young, carefully selected product, free from disease and from accidental impurities which might render the product unwholesome or unpalatable.
=Truffles.=--The truffle has been known almost, if not quite as long as the mushroom as an edible delicacy. The use of truffles in France became very common during the 14th century, but on account of their high price they remained for a long time a luxury and not a general article of commerce. It is only within the 19th century, after 1840, that their consumption became general. The truffle belongs to the botanical family Tuberaceæ.
The propagation of truffles is similar to that of mushrooms, by spores, which first give rise to a mycelium which by further condensation forms the body of the truffle. This mycelium furnishes the nutritients for the tubercle during a certain time of its early growth. In the cultivation of the truffle, artificially, it is necessary to make use of a forest or other similar artificial covering. If trees are planted especially for the development of truffles it requires six or eight years growth before the cultivation of truffles is successful. The truffle grows very readily in the shade of nut-bearing trees and in the shade of the oak. The mycelium does not produce truffles until after several years of vegetation. When it once begins to fructify and produce the truffle it continues to bear for many years. The truffle, like the mushroom, grows rapidly. At first, as has already been stated, it is nourished by the mycelium, but when this is exhausted it is nourished by absorbing the nutritious elements from the soil and air. When it reaches maturity and its spores are well formed the truffle acquires its maximum of aroma and palatability. After it has reached maturity it can remain a certain time in the soil without being changed. However, after a time it is rapidly decomposed and its tissues become the seat of various chemical reactions or it is devoured by insects.
Cultivation of Truffles.--The truffle may only be grown in the midst of very favorable conditions of climate, altitude, mellowness of the soil, moisture, and proper shade. The planting of truffle trees serves as a vehicle for the spores which are later to give birth to the mycelium which itself produces the truffle. The spores of the truffles usually reach the forests in which they are grown by natural means without being particularly planted. Sometimes, however, the spores are carried directly to the soil where the new crop is to be grown.
Geographic Distribution.--The truffle, like the mushroom, is spread over all parts of the earth. In Europe it is especially abundant in France and Italy. The provinces in France where it grows in greatest abundance are Provence, Dauphiné, Languedoc, and Périgord.
Principal Varieties.--The varieties of truffles are not so numerous as mushrooms, of which perhaps a thousand different varieties are known, but still they are sufficiently numerous. One of those frequently cultivated in France is known as truffles of Périgord (Tuber melanosporum Vittad.). It grows best under the shade of a growing walnut or a young oak. The tubers of these plants, which are the part valuable for food, may weigh from 60 to 500 grams. Other botanical varieties which are much cultivated are Tuber brumale Vittad., Tuber æstivum Mich., Tuber magnatum Vittad., and many others.
Harvesting of Truffles.--The truffle comes into production from the sixth to the tenth year after planting the appropriate forest trees. It is easy to determine the year when the harvest should begin, since during the preceding year there is found in the soil some hypogæan mushrooms which may be considered as precursors of the truffles. Moreover, the soil under the tree becomes practically free of all vegetation. The truffle ripens from November to April, according to its variety. It is important that it should not be harvested except at the period of complete maturity. For harvesting purposes certain animals are made use of, such as the dog and hog. These animals have a delicate smell in these matters and only bring out of the soil the ripe truffles while they leave the others. Man is not able to make this nice distinction, and harvests all indiscriminately, from which there results great financial loss. In the harvesting of truffles the ground should be gone over about once in eight days in order that the tubercles may be secured during the whole winter at the proper time of maturity. When the truffles are developed the soil above them is hilled or cracked, especially after rains. These are the places which are selected for the harvesting when it is done by the hand of man.
Harvesting by Means of Flies.--When the weather is warm and clear there is seen above the place where the tubers are lying, a multitude of flies,--these mark the place where the harvest should be made. The best time for this kind of a harvest is about nine o’clock in the morning. Good results are not obtainable from this sign except when the sun rises clear and becomes afterward warm. In order to find the flies the husbandman stoops down near the surface of the soil and looks horizontally over it. The colonies of flies are thus easily distinguished, and below each one of these colonies the truffles are found. This is also an ineffective method because only the overripened tubercles attract the flies while those in their very prime are not thus marked.
Harvesting with Hogs.--The utilization of hogs for harvesting purposes is by far the best and most economical method. It is employed especially in Périgord and Midi. The harvesting can be either in the morning or afternoon. The hogs which are used for harvesting should be previously well fed in order to prevent them from eating the truffles which they dig out of the ground. Each animal is led with a rope. As soon as the hog gets the scent of truffles it pounces upon them and rapidly uncovers them with its snout. When the weather is favorable a hog can easily smell a truffle at a distance of 150 feet. As soon as the animal has brought the truffle to the surface instead of allowing him to eat it he should be recompensed by giving him some suitable food such as maize. If this little attention is neglected the animal soon becomes discouraged and refuses to work any longer. Before leaving the spot the hog assures himself that no other truffles are contained in that neighborhood. When the hog becomes very tired he walks very slowly and with his mouth open. It is then necessary to give him a period of rest before continuing the harvest. If the search for truffles does not bring good results the animal becomes morose, indolent, and refuses to obey. Sometimes when the hog is hungry and wants to eat the truffles it is necessary to give him a smart blow on the snout with a stick. A special race of hogs is used in this harvesting whose parents have also possessed the skill, and thus it becomes hereditary. A good hog is able to engage in the harvesting from the age of two to 25 years but they do their best work at three or four years. A single animal may be able to harvest from six to 40 pounds of truffles per day, according to their abundance in the soil. This class of hogs have a very high value, and are often sold in the south of France for this sole purpose at from $30.00 to $70.00 per head.
Harvesting with the Dog.--The dog is also employed in regions where truffles are produced, and especially in those regions where the yield is not so great and where the area to be gone over is very large. The dog is used especially in the Dauphiné, Champagne, Bourgogne, Provence, and Languedoc, and also in the neighborhood of Paris. These dogs are trained, as in the case of hogs, especially for this purpose and should be rewarded when a find is made, in the same manner as the hog. This recognition of their services should never be forgotten if animals of the greatest skill are to be secured. The dog, as is the case with the hog, locates the truffles by the scent and digs with his four paws until the truffles are laid bare,--the husbandman then draws them out of the soil with long forceps. The hog is preferable to the dog because it does the whole harvesting itself, whereas in the case of the dog the husbandman must finish the operation.
The yield of the truffle farm is naturally extremely valuable, varying with the relative abundance of growth and character of the soil itself. Sometimes the yield drops as low as five pounds per acre and sometimes rises as high as 70 pounds per acre. The average price of truffles is $2.00 per pound. The largest yield is found in the truffle farms from the tenth to the twentieth year.
Properties of Truffles.--It is difficult to describe the properties of truffles. They are, when prepared for the table, black, rather firm in flesh, and have a distinct and most agreeable odor and taste. A good truffle is extremely firm and resists the ordinary pressure of the finger. If it is soft it shows that it is lacking in its best characteristic.
The size of the truffle has a marked influence upon its value because the small truffle loses a large part of its weight in the preparation for eating. Truffles of good size are those which weigh from 40 to 50 grams, those of first choice weighing from 60 to 100 grams. After the truffle passes 100 grams in weight the increased weight does not proportionately increase the value. The truffles which come from light soil are considered superior to those which come from rich soil. If the soil contains a large quantity of iron the truffles are usually of finer quality. All truffles are not black, though the best ones, like those of Périgord, are black. Others are gray or brown.
Adulteration of Truffles.--Commerce in truffles is the subject of considerable fraud on account of the very high price of the genuine article. The principal adulterations are the mixture of the inferior or imperfect varieties with the choicest or best varieties. This adulteration is easily discovered by making a careful examination of the tubercles individually. Another fraud which is very much practiced is the introduction of soil into the cracks or crevices in order to increase their weight. This adulteration, of course, is easily discovered by anyone who prepares the truffles for the table. Another form of adulteration is the mingling with the ripe truffle of those which have not reached maturity. The unripe tubercles have very little flavor or taste and are thus easily distinguished from those which are mature. Also practiced is the pressing together with some kind of a glue of a number of smaller truffles in order to form a large mass, as if it were an entire truffle, and thus securing a larger price. This is also a fraud easily discovered. Still another form of sophistication is the production of artificial truffles made from potatoes and especially those which are partially spoiled which are colored in imitation of the truffle itself. Only those who are ignorant of the texture of the truffle can be deceived by this gross imitation. Another form of adulteration is the sale of the truffle coming from regions less esteemed for their products for those of other more esteemed regions as for instance, the sale of truffles from Sarladais or from Domme for those of Périgord.
Preservation of the Truffle During Transit.--For the purpose of keeping truffles in good condition during transit they may be placed in moss, fine sand, or powdered chalk. They can be kept in this way for a few days during transit, but should not be long preserved in this manner. Truffles may also be preserved indefinitely by sterilization. It is necessary to do this whenever they are to be sent over long distances or kept for a long time. The methods of sterilizing are not different from those described for ordinary vegetables. Truffles are also preserved by desiccation, but in this case they lose something of their odor and taste and are not so highly esteemed. Finally the truffles are sometimes preserved by cooking them and preserving them in wine or olive oil. (Raymond Brunet, “Manuel Pratique de la Culture des Champignons et de la Truffe.”)
=Food Value of Fungi.=--While the mushroom and the truffle are the principal fungi used as food they are by no means the only kinds. Their value, as has already been indicated, is rather condimental than nutritive. Those, however, who have eaten fresh or well preserved mushrooms or truffles, cooked in the best style of the culinary art, are fully acquainted with their value. The fear of poisoning does much to restrict the use of the wild mushrooms. The fields and forests are full of many varieties of these fungi, especially in the autumn. Very few of the varieties are poisonous, but the conservative gourmand hesitates to consume the fruits of his own activity as a collector. In the hills of the Blue Ridge Mountains near Harper’s Ferry I have seen large areas of the forest almost covered with these growths in August and September, but the courage leading to their consumption was wanting.