Cheddar cheese making

Preface To Second Edition

In the past few years great advances have been made in cheese making, and for the old rule of thumb, definite scientific reasons have been substituted.

During the first three years of the Wisconsin Dairy School, the theoretical part of the instruction in cheese making was given by a series of lectures and quizzes along with the practical work.

All books treating on cheese making were either out of date, because of the rapid advance in knowledge on the subject, or were unfitted for use as text books in a school.

The instructor has learned by experience that in order to have the students properly grasp the subject before them, they must have a text book for use along with the lectures and quizzes, in short, with the advent of dairy schools, cheese making in pedagogic form was a necessity.

There are other cheese makers who are not students in dairy schools and it was hoped that they might also find information in the book that would help them. This was proven to be true by the rapidity with which the first edition was exhausted, and the present edition has been revised with a view to more fully meeting the needs of such persons.

Part I deals with the fermentations of milk and the process of making.

Part II deals with the construction and operation of factories.

Part III consists of questions which are answered in the text of parts I and II. The page on which the answer to the question may be found is indicated at the end of the question.

Important Points are indicated by paragraph headings, and usually the answer can be immediately found by glancing at these.

The writer believes that the questions in Part III will not only be helpful to students of dairy schools in mastering the subject, but that they will also be of aid to all students of cheese making.

A careful study of the questions is urged, however simple they may seem, as an accurate knowledge of the details and the reasons why, of the various steps in the process is absolutely necessary in order to master the profession.

Chapter I. Milk

Composition of Milk. Milk is a secretion of mammals for the nourishment of their young. If we examine the milks of different mammals, we will find that they are composed of the same substances, but that these substances vary in their proportions, as will be seen from the following table giving the composition of milks from different origins:

Ash (chiefly Phosphates).... .5 .7 .4 .6 .7 .9

As American cheese is made from cows' milk only, no consideration will be given any of the other kinds of milk.

That we may have a better idea of milk, let us look at the nature of the substances in its composition.

Albuminoids. The albuminoids or protein compounds contain about sixteen per cent, of nitrogen, and are the muscle forming part of the milk.

Milk Sugar. The sugar of milk crystallizes in hard crystals, which are neither as soluble nor as sweet as cane or ordinary sugar. Commercial milk sugar is used largely in the manufacture of lactated foods.

Ash. The ash is the mineral substance left when milk is burned. Chemical analysis shows it to consist largely of phosphates. • The ash is the bone-forming part of the milk.

Water. The albuminoids,* milk sugar and ash are all in solution in the eighty-seven per cent, of water.

Fat. The fat of the milk is not in solution, but in the form of little globules suspended in the liquid portion, which form is called an emulsion.

MICROSCOPIC MILK AS DRAWN FROM THE COW.

The globules vary in size from one two-thousandth to one ten-thousandth of an inch in diameter. By one ten-thousandth of an inch is meant that it would take ten thousand of these little globules placed side by side to make a row an inch long.

*The casein, which is an albuminoid, is thought by some authorities not to be in solution, but in the form of a thin gelatinous mass. This point however is disputed, and for all practical purposes we can speak of it as in solution.

Colostrum Milk. The first milk given by a cow just after calving is called colostrum milk, and is much more viscous than normal milk, sometimes being nearly as thick as syrup. The components of the milk are not in their normal proportions, the albuminoids sometimes amounting to fifteen per cent, of the milk, while the fat may be less than two per cent. Under the microscope, cells which have scaled off from the inside of the udder can be seen floating about, and while these dead particles of tissue are in the milk, it is unfit for cheese. After four or five milkings the milk will appear normal, but it should not be used for a week.

MICROSCOPIC MILK AFTER STANDING A SHORT TIME.

When milk is taken into the calf's stomach, it is digested by the juices secreted by the same. If we take a stomach and soak it in water or brine, two ferments, rennet and pepsin, the active principles in digestion, are dissolved; and if we add this solution to milk, the milk will be curdled. The part of the milk that is curdled is the casein, which is the larger portion of the albuminoids. About one-fourth of the albuminous substance in the milk is like the white of an egg, and is not coagulated by rennet. By heating the whey after the casein has been first coagulated, this part will be precipitated, and therefore seems to be identical with the albumen of an egg, which is also coagulated by heat, as is seen in cooking, and is called lactalbumen.

Whey. In the manufacture of cheese the milk is curdled by rennet, and the curd cut into small pieces from which the liquid portion, or whey, is expelled. The whey then is the major part of the water of the milk, which carries with it nearly all the soluble portions, namely: the albumen, milk sugar, ash, and also a small portion of the fat, as the very small globules break away from the curd in cutting it.

Curd. The curd, or green cheese, is the coagulated casein which holds in its meshes most of the fat, some water, and small portions of the albumen, milk sugar and ash. The water in green cheese is about one-third of its weight. We look upon green cheese and curd as identical, for green cheese is simply curd pressed together.

Fat Necessary for Cheese. While the casein may be said to be the cheesy part of the milk, still the quantity and quality of the cheese produced is greatly affected by the quantity of fat present in the milk; in fact, the real value of milk for cheese is determined by the amount of fat it contains. Without the fat the casein will dry out very rapidly and become very hard. The fat not only helps the casein to hold the water from excessive evaporation, but it seems to increase the capacity of it for absorbing water.

Chapter II. The Fermentations Of Milk

Cheese making a Process of Fermentation. The

process of cheese making is a process of fermentation from beginning to end. It will therefore be necessary to consider the different kinds of ferments, and how they act in the process. There are two general kinds of ferment, namely: organized and unorganized.

Organized Ferments. The organized ferments are so called because they are the result of the growth of minute vegetable organisms. There are millions of these organisms in the milk, and in their growth they decompose the components of the milk, forming varying decomposition products. Nearly all the trouble we have in cheese making is due to the action of definite living vegetable cells that have the power of manufacturing certain decomposition products; on the other hand, we could not produce fine cheese without the presence of certain forms of bacteria that are able to change the milk, producing the fine desired flavors.

Lactic Ferment. The souring of milk is produced by the growth of particular species of organized ferments. These organisms so affect the milk sugar that it is changed into lactic acid. When the lactic fermentation is not properly handled and there is too much lactic acid formed in the curd, we have a sour cheese, and on the other hand when the curd is put to press before the lactic fermentation has run its course, gas is produced, which forms large, round, smooth holes, termed ' 'Swiss holes," so-called because they resemble the holes found in Swiss cheese.

Important Point in Cheese making. The most important point in cheese making is to know how to control the lactic fermentations.

Pinholey Curds due to Bacteria. But the ordinary souring of milk, or lactic fermentation as it is called, is not the only fermentation due to germs or bacteria. Through the action of the lactic ferment the milk sugar is decomposed, but in other fermentations the casein is attacked, and gas formed that collects in little holes about the size of the head of a pin, and such a curd is therefore known as "pinholey."

Butyric Ferment. Bacteriologists have separated quite a number of peculiar ferments that are produced by distinct species of bacteria; for instance, there is the butyric fermentation, in which butyric acid is the decomposition product formed, and the alcoholic fermentation in which alcohol and carbonic acid gas are formed.

Bitter Milk — How Caused. There is also sometimes a bitter taste to milk which usually goes with the butyric fermentation, but bacteriologists have shown it to be the result of a distinct fermentation.

Alkaliue Fermentation. Another peculiar fermentation of milk is the alkaline curdling, in which the milk curdles apparently in the same manner as in or-

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dinary souring, but it shows a distinct alkaline reaction. "Ropy" and "slimy" milk are also fermentations that are brought about by the action of bacteria.

Yeast Plants

Bacteria. It has been said that these fermentations are due to minute living organisms. They are, in fact, little plants consisting of but a single cell, and these little cells live and grow in a similar way as do larger plants that we can see without a microscope.

On the outside is the cell wall which resembles the shell surrounding an egg- Inside of the cell wall is the protoplasm, or living element of the organism. Some of these single cells are spherical in form, and are known as cocci (singular, coccus), others are rodlike, and are called bacilli (singular, bacillus), meaning a rod, and the yeasts or saccharomyces, which grow in sugar solutions and are oval in form, are still another class. The protoplasm or living element inside of the cell wall is sensitive to light and heat just as in the higher order of plants; in fact, these characteristics are the characteristics of life, and anaesthetics, such as chloroform and ether, will cause a cessation of their vital activities, and the fermentation ceases entirely because the protoplasm is killed, or is suspended until the irritating agent is removed.

Difference between Organized and Unorganized Ferments, This is the distinguishing difference between organized and unorganized ferments, the latter class not being affected by anaesthetics. For instance, rennet will curdle^ milk, and its action is hastened or retarded according to the temperature of the milk, the same as organized ferments, but it is not affected by these protoplasmic poisons.

Rennet is a good representative of the unorganized ferments or enzymes, as they are called, with which we have to deal in cheese making.

Enzymes. The enzymes do not seem to be living organisms, but are more like a chemical in their action. On the other hand, they hardly seem to be purely chemical, for a chemical will be used up by entering into another combination, but an enzyme may be used over and over again.

Enzymes sometimes produced by Organized Ferments. While enzymes are distinct from organized ferments, they are often produced as a result of the growth of certain organisms. In the alkaline curdling of milk, mentioned among the organized ferments,

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there is an enzyme produced as a result of the growth of the bacteria, and then the curdling is accomplished by the enzyme in a manner similar to, if not quite identical with that of rennet. Rennet and pepsin, the active part of the rennet extract used in cheese making, are both enzymes.

Rennet, where found. Rennet which was first isolated by Hammersten, is found in the stomachs of calves, lambs and pigs, and also in birds and fishes, and in some plants.

It will be remembered, by referring to the table showing the composition of milk, that there is 0.7 per cent, ash in cow's milk, which is a comparatively small quantity.

Phosphates required. Part of this ash is in the form of phosphates, and though small in quantity, rennet will not curdle the milk without their presence. It is thought that casein forms a chemical combination with the phosphates in the form known as casein tricalcium phosphate, which is soluble, but when rennet is added to the milk, it is changed to calcium phosphate and an insoluble casein compound which is the cheese.

Effect of Salt on Milk. If common salt or magnesium sulphate is added to the milk in sufficient quantity, the casein will be precipitated.

Effect of Heat on Rennet. Rennet will not curdle milk at a very low temperature, but as the temperature is raised it will begin to work and act with increasing rapidity until at a point above iOO° F. it is injured. By putting cold rennet into warm milk it may work faster up to 120 or 130° F. , but when the rennet in weak solutions is heated to 105° F. it begins to be injured. A strong solution maybe held at 150 for fifteen minutes without being entirely destroyed, but it will be rendered much weaker. These high temperatures do not destroy the power of the rennet instantly but gradually.

Rennet does not Exhaust Itself. As has been said concerning enzymes, rennet does not seem to spend its energy, but will act over and over again. If we coagulate a quantity of milk, and apply the whey to a like quantity of milk, the milk will be coagulated; we could do this indefinitely, if it were not for getting a larger volume of whey than we have of milk.

Effect of Acidity on the Action of Rennet. It has

been said that the rapidity in the action of rennet is greatly affected by the temperature of the milk, but we will find, if the temperature of the milk is held constant, the more lactic acid there is in the milk the faster the rennet will act, or if any acid be artificially added to the milk in quantities not sufficient to coagulate it, the action of the rennet will be hastened, and on the other hand if alkali be added to the milk, the action of the rennet will be retarded.

Rennet Extracts not alike. Another cause for varying rapidity of action is the difference in the strength of the rennet extract used. Rennets vary as to the amount of ferment contained in them, and it is next to impossible to get two lots of rennet extract exactly alike.

Rennet is sometimes concentrated in the form of tablets or rennet powder, but even these vary in strength, and they are concentrated to such a degree that it is difficult to measure them closely, and on that account extract is preferable.

What Rennet Extract is. Rennet extract is a solution of rennet and pepsin in strong brine. A rennet, as we buy it on the market, is a calfs stomach, which has been cleaned and filled with salt and allowed to dry. The best rennets come from Bavaria.

How Rennet Extract is Made. Rennet extract is made in the following manner:

Prepare a sufficient number of rennets, say five hundred, by splitting them open so that the water can get into them. Then take an oak barrel and put the rennets into it, and fill with water until they are well covered.

Possibly the barrel might be nearly filled with water, but we should not have more water than is necessary to dissolve the ferment.

A little salt should be added to the water, say three pounds of salt to one hundred pounds of water. The rennets should be stirred up and pounded every day, to facilitate the solution of the ferment, and at the end of a week the liquid should be drawn off and the rennets wrung out with a clothes wringer. They should be put into water again and soaked for another week, and the same operation gone through with. As a usual thing, the ferment has not all been extracted from the stomachs till they have been soaked for four weeks. The liquid that has been obtained by soaking the rennets should be filtered through clean straw, charcoal and sand, and then an excess of salt added to preserve it.

The extract should be clear though of a dark color. The first sign of the decomposition of rennet extract is a muddy appearance.

If extract is ever prepared by the cheese-maker, enough to last the whole season should be made in the spring when the weather is cool, and then it should be kept in a cool place.

Reliable Brands to be Preferred. The surest way of getting extract that can be depended on, is to buy some reliable brand of extract, such as Hansen's.

The practice of preparing extract every few days is wrong, as the strength of each new lot will not be like the last, and if used in about the same quantities the cheese will not cure evenly. The use of whey as a solvent for the rennet is wrong for reasons that are obvious after considering the subject of organized ferments.

A comparison of extracts and their relative value, will be taken up after the rennet test has been explained.

Chapter III. The Rennet Test

Cause of Uneven Cheese. Cheese makers have had trouble in getting their cheese even in quality. If the milk came in cold in the morning and the rennet was added to it immediately on warming it up to the proper temperature, the development of acid was retarded; and if they put it to press before sufficient acid had been formed, they would get a sweet flavored cheese full of "Swiss holes." If the curd was held in the whey long enough for proper development of acid, the chances were that it would become whey-soaked, and a leaky sour cheese would be formed. Or if the milk was over ripe, it would work too fast and the cheese would be sour.

As early as fifty years ago, in England, the cheese makers began to learn that if milk was cold, they would obtain better results by warming it up to 90 F. and allowing it to ripen before adding the rennet; but while it improved the quality of the cheese, it did not always help them out of the difficulty.

Rennet Action dependent on Three Things. It has

been shown that the rapidity with which rennet coagulates milk is dependent on: —

1. The strength of the rennet extract.

2. The temperature of the milk.

3. The acidity of the milk.

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Now if we use the same rennet, at the same temperature of the milk each time, the variation in the rapidity with which it coagulates the milk, must be due solely to the acidity or ripeness of the milk.

J. B. Harris discovers the Rennet Test. About ten years ago J. B. Harris conceived this idea, and used a teacupful of milk from the vat, to which he added a teaspoonful of rennet and noted the number of seconds required to coagulate the milk. When the milk was ripened down to a certain number of seconds, he found that he could foretell approximately the time that it would take for acid to develop.

Rennet a Powerful Agent. But if one stops a moment to figure on it, he will see that rennet is a very powerful agent. If one uses four ounces of extract to one thousand pounds of milk, it is one part of rennet to four thousand of milk, and sometimes the proportion will be as wide as one to sixteen thousand. It will be easily seen that since the rennet is such a powerful agent, it is not likely to be an entirely accurate test where a teaspoon is used for measuring the rennet, for then it would be difficult to measure exactly twice alike. Therefore, in place of the teaspoon, a minim or dram graduate was substituted, and for the tea cup an eight ounce glass graduate such as druggists use. This was much better than the other crude apparatus for making the test.

Glass Graduates for Measuring. But the minim graduate is funnel shaped, and the top being broad in proportion to its volume, the chances for error are i6

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still too great in measuring. In actual practice through haste in making the test, two or three drops of extract were likely to be left in the narrow bot-

\Ocz.

GLIocss GUrccdtcates torn of the minim graduate, and the maker would be confused in not getting the results he expected by depending on it.

J. H. Monrad then proposed a new set of apparatus, which, though not so simple, leaves less chance for error.

The Monrad Rennet Test. The apparatus for the Monrad test, as used at the Wisconsin Dairy School, consists of a 160 c.c. tin cylinder for measuring the

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milk, a 5 c. c. pipette, a 50 c. c. glass flask, and a half pint tin basin. By filling the tin cylinder full it always gives the right measure of milk quickly. Measuring the milk in a- glass graduate is difficult, as it is hard to get the milk just to the mark, and if the glass is covered with white milk it is difficult to see the mark.

MONRAD RENNET TEST.

The rennet is first measured with the 5 c. c. pipette. A pipette (as will be seen by reference to the illustration), is a glass tube with a mark on it indicating the volume of 5 c. c, and the rennet can very easily be measured to the mark, and the tube being narrow makes the measurement accurate. The rennet in the pipette is delivered into the 50 c. c. flask, and what little rennet adheres to the inside of the pipette is rinsed into the flask. This is then filled with water to the 50 c. c. mark on the neck, and the solution mixed by shaking. The milk, the temperature of which should be 86° F. , measured in the tin cylinder, is emptied into the half pint basin, and 5 c. c. of the dilute extract is measured into the 160 c. c. of milk, and the number of seconds required to curdle it noted. If a few specks of charcoal are scattered on the milk and the milk started into motion around the dish with a thermometer, the instant of curdling can be noted by the stopping of the specks. They will stop so suddenly as to seem to start back in the opposite direction.

Use Thermometer to Stir Milk. By using a thermometer, the temperature can be constantly watched; and if the temperature should fall, it can quickly be brought back to 86° F. by setting the basin in a pail of warm water for five seconds.

Ripening the Milk. If the milk is ripened so as to coagulate in the same number of seconds each day, one can tell very closely the time when the whey can be drawn off from the curd. It should be ripened to a point where in two hours from the time the rennet is added to the milk there will be ''one-eighth of an inch of acid " on the curd, as we shall see later on.

With the rennet extract we have been using at the Wisconsin Dairy School, the milk when ripened to thirty seconds works off in about the right time, but the extract is very strong, one ounce being sufficient to coagulate one thousand pounds of milk in twenty minutes. If however our rennet extract was so weak that it would take four ounces of it to coagulate one thousand pounds of the same milk in twenty minutes, it would be only one-fourth as strong as the rennet we have been using, and the milk would then have to be ripened so as to coagulate in one hundred and twenty seconds instead of thirty.

How to Ripen Milk to the Right Point. Starting in with the season's work the cheese maker has nothing to guide him as to the ripeness of the milk, simply because he does not know the strength of the rennet extract at his disposal. The first day he makes cheese, he must make a rennet test of his milk at the time he sets it and then observe how the milk acts. If the milk is too sweet, he can calculate about how much riper it must be to work just right, and in a few days he will have the matter entirely under his control. Cheese makers should never neglect to use the rennet test, for it enables them to judge definitely the condition of their milk.

When a maker is troubled with tainted milk it is often necessary to ripen a little lower than with good milk, for the bad flavor, as we have already learned, is due to some harmful variety of bacteria which choke out the lactic ferments.

Use of a Starter. In such cases it is well to use a starter to make the lactic ferment overcome the other ferment. (See p. 24.)

Comparisons of Rennet Extracts. Sometimes, as has been previously shown, it will take three or four ounces of one kind of rennet extract to coagulate one thousand pounds of milk at the same temperature and time, as it would take one ounce of another extract. Perhaps the weaker extract is offered for sale at a lower price. By using the rennet test to compare the two kinds of extract, one can toll their relative values.

How to compare Milks. In comparing two lots of milk, for that is just what we do with the rennet test, we must have all the conditions other than the milk the same; that is, we must use the same extract, at the same temperature every time, and the test will tell us the strength of acid in the milk.

Now if we want to compare two kinds of rennet extract, we must have all the conditions but the extract the same; that is, we must make the tests at the same temperature, on the same milk, and at the same time, for the milk will be ripening and introducing an error if we wait. When these conditions are followed the test gives us the comparative strength of two kinds of rennet extract, and we can afford to pay for them in proportion to their strength with perhaps a preference for the stronger extract, other things being equal, for the stronger extract will invariably keep better.

An Example in Cost of Extract. Suppose two kinds of extract, A and B, are offered to us and the price of A is $1.50 and B $1. 25 per gallon. On making comparative tests of them, we find that A coagulates the milk in thirty seconds and B in fifty seconds. Which extract is the cheaper?

We simply put the problem into an inverse proportion. 30 : 5o::.r :$i. 50.

The product of the means equals the product of the extremes.

From which we find that we can afford to pay 90 cents for B extract and $1.25 is too much for it.

Aii Example Requiring Time for the Answer.

Let us continue the above example. Suppose after stating the comparative rennet tests of A and B extract the question asked was, if four ounces of A will coagulate 1,000 lbs. of milk at 86° F. in twenty minutes, how long will it take five ounces of B? We cannot compare four ounces of A with five ounces of B directly for they are not of the same strength. The first step will be to find how long it will take four ounces of B, and having found it we can in the next step compare four ounces of B with five ounces of B. When we use 1,000 lbs. of milk and four ounces of rennet, we are simply making a rennet test on a large scale, and A and B will have the same ratio as though 160 c. c. of milk and .5 c. c. of rennet were used.

First step. We put down our first ratio 30 : 50. As x y the time it will take fourounces of B extract, will be greater than twenty minutes, we put x in the fourth place, and our proportion reads 30 : 50 :: 20 : x.

The product of the means equals the product of the extremes

. \ 30^=1,000

jt= 33^ minutes,

the time required for four ounces of B to coagulate 1,000 lbs. of milk.

Second step. If four ounces of B will coagulate the milk in 33^ minutes, five ounces will coagulate it in less time than four ounces. We accordingly make the following proportion:

An example requiring quantity for an answer. Continuing the example how much A extract will be required to coagulate 1,000 lbs. of milk at 86° F. in thirty minutes?