Food industries; an elementary text-book on the production and manufacture of staple foods, designed for use in high schools and colleges

Preface

After many years' experience in lecturing on the processes of food manufacture, the authors feel encouraged to submit the result of their labors as a guide to those who wish to study this most important and interesting subject.

Certainly no branch of general manufacturing has undergone so many and such important changes in the past twenty-five years as the food industries. The public have largely benefited from these changes both in pocket and health.

Unfortunately there still lingers in the minds of many, the impression that food stuffs have not the same dietetic value they possessed in the past, and that manipulation gives them an appearance of quality they do not possess. It is the universal experience of the authors that manufacturers have not only improved the quality of their products in every possible way, but having nothing to conceal except from competitors, are most anxious to enlighten the interested consumer in the processes involved.

Some mistakes have certainly been made in the past, but with no evil intent and largely through ignorance. As time passes these errors are corrected and it can confidently be stated that the public receives to-day better and cleaner material .at a lower price than formerly. The economic improvement is largely due to the general utilization of by-products, many of which do not appear in any list of foods.

The following pages do not claim to deal with any industry from the purely technical standpoint, but aim to point out the most essential parts of each. A knowledge of chemistry and physics is not absolutely essential but is very helpful.

As a pioneer book on the subject any suggestions furnished by teachers would be very gratefully received.

The authors are greatly indebted to Dr. H. C. Humphrey, Dr. W. D. Home, Dr. W. E. J. Kirk, Mr. George S. Ward, Mr. Chauncey E. Foster, Mr. Ernst Mlihlhauser and Mr. R. E. Tomlinson for valuable suggestions in regard to the subject matter of this book and to Mrs. Ellen B. McGowan of Teachers College for reading the manuscript. They wish also to acknowledge the assistance of the many manufacturers who have thrown their plants open for inspection and who have allowed the use of photographs and cuts of machinery.

September, 1914. July, 1916.

Contents

PAGE

Introduction 1-4

Chapter I — Food Principles 5—16

Functions. Conservation of Energy. Elements in Foods. Food Principles. Examples of Each Group. Functions of Each Group. Carbohydrates. Classifi- . cation. Formation. Occurrence Important Properties. Fats. Composition. Occurrence. Properties. Proteins. Composition. Classification. Occurrence. Properties. Importance of Water.

Chapter II — Water 17-37

' Classification of Natural Waters. Water Supply. Historical. Classification of Potable Water. Atmospheric. Surface Water. Subsoil Water. Pollution of Wells. Contamination of Public Supplies. Danger of Impure Water. Diseases from Water. Purification. Artificial Methods. Bacterial Action. Filtration. Use of Sterilizing Agents. .Distillation. Household Methods. Boiling. Use of Domestic Filters. Judging a Water Supply. Ice Supply. Mineral Waters. Natural Mineral Springs. Occurrence. Medicinal Value. Artificial Mineral Waters.

Chapter III — Cereals 38-49

Biological Origin. Geographical Distribution. Use in our Country. Indian Corn or Maize. Origin. Cultivation. Varieties. Early Methods of Preparation. Old Milling Methods. Samp. Hominy and Cornmeal. Modern Milling. Uses. Adulteration. Rice. Origin. Geographical Distribution. Composition. Cultivation. Milling. Adulteration. Uses. Oats. Composition. Oatmeal. Milling. Adulteration. Barley. Origin. Cultivation. Composition. Uses. Mill Products.

Chapter IV— The King of Cereals. Old Milling Processes 5°~^3

Wheat. Origin. Geographical Distribution. Cultivation. Structure of the Wheat Grain. Value of Wheat. Varieties. Old Milling Processes. Handstones. The Pestle and Mortar. The Quern. The Grist Mill. Disadvantages of Old Processes.

CONTENTS V

PAGE

Chapter V— Modern Milling and Mill Products 64-78

Dust Collectors. Fundamental Objects in Milling. Cleaning of the Wheat. Tempering. Separation of the Middlings. Reduction of the Middlings. Advantages of the New Process. Testing of Flour. Wheat Blends. Adulteration. Bleaching. Mill Products. Hard Wheat Flour. Soft Wheat Flour. Prepared Flour. Graham Flour. Entire Wheat Flour. Gluten Flour. Cereal Department. Rye. Composition. Uses. Adulteration.

Chapter VI — Breakfast Foods and Coffee Substitutes. . 79-85 Breakfast Foods. Classification. Uncooked. Partly Cooked. Cooked. Malted Preparations. Adulteration. Comparison of Old and New Cereals. Coffee Substitutes.

Chapter VII- — Utilization of Flour. Breadmaking. . . . 86-112 Primitive Breadmaking. Leavened Bread. Yeast. Leavening Effect of Yeast. Yeast Preparations. Home Brew. Brewer's Yeast. Compressed Yeast Cake. Dried Yeast. Salt Rising. Object in Breadmaking. Steps in Breadmaking. Fermentation. Straight or Off-Hand Dough. Ferment and Dough. Sponge and Dough. Baking. Cooling. A Modern Bread Factory. Souring and Its Prevention. Adulteration. Losses in Fermentation. Aerated Bread. The Cracker or Biscuit Industry. Macaroni.

Chapter VIII — Leavening Agents 1 13-122

Advantages and Disadvantages of Yeast. Chemical Agents. Baking Powders. Tartrate Powder. Calcium Phosphate Powders. Sodium Phosphate Powders. Alum Phosphate Powders. Ammonia Powders. Cream of Tartar. Tartaric Acid. Acid Phosphate of Lime. Bicarbonate of Soda. LeBlanc Method. Solvay Process. Niagara Process.

Chapter IX — Starch and Allied Industries 123-135

Starch. Composition and Formation. Physical Characteristics. Properties. Uses. Source of Supply. Potato Starch. Extraction. Processes in Manufac-

VI CONTENTS

PAGE ture. Tapioca. Corn Products Industry. Processes in Manufacture. By-products and Their Uses. Dextrins. Corn Syrup or Glucose. Processes in Manufacture.

Chapter X — The Sugar Industry 136-158

Source. History of the Sugar Cane. History of the Sugar Beet. Comparison of Cane and Beet Sugar. Properties of Sugar. The Cane Sugar Industry. Growth of the Cane. Production of Raw Cane 1 Sugar. The Beet Sugar Industry. Beet Culture.

Production of Raw Beet Sugar. Refining of Raw Sugar. Granulated Sugar. Block Sugar. Powdered Sugar. Utilization of the By-products. Yellow Sugar. Maple Sugar. Date-palm Sugar. Sorghum. Cane Syrup. Adulteration.

Chapter XI — Fruits, Vegetables and Nuts 159-168

Importance in the Diet. Definition and Classification. Composition. Cultivation. Handling on the Farm. Transportation and Storage. Marketing. Candied Fruit. Jams, Jellies, Marmalade, Fruit Butter. Nuts. Composition. Digestibility. Nut Products.

Chapter XII — Alcoholic Beverages 169-180

Classification. Historical. Fermentation. The Brewing of Beer. Raw Material. Processes in Manufacture. Composition of Beer. Adulteration. Substitution. Kinds of Beer.

Chapter XIII — Alcoholic Beverages (Continued) 181-191

The Wine Industry. Processes in the Manufacture. Champagne. Sophisticated Wines. Adulteration. By-products. Distilled Liquors. Brandy. Rum. Whiskey. Liquers. Cordials. Gin. Cider. Vinegar. Koumiss.

Chapter XIV — Fats 192-204

Extraction. Purification. Butter. Composition. Processes in Butter-making. Renovated Butter. Oleomargarine. Olive Oil. Cottonseed Oil. Peanut Oil. Coconut Oil.

CONTENTS Vll

PAGE

Chapter XV — Animal Foods 205-223

Meat. The Physical Structure and Chemical Constitution. Meat Inspection. Diseases of Animals. Reasons for Cooking Meat. Changes in Cooking. Beef Extracts. Beef Juices. Internal Organs. Fish. Shellfish. Oysters. Clams. Scallops. Mussels. Lobsters. Crabs. Poultry. Eggs.

Chapter XVI — The Packing House 224-232

Historical. Growth and Breadth of the Industry. Processes in the Packing House. Inspection and Slaughtering. Use of By-products. Hides. Fat. The Feet. Bone Products. Tankage. Blood. Mixing Fertilizers. Glue and Gelatin. Canning of Meat. Beef Extracts. Sausages. Minor Products.

Chapter XVII— Milk 233-246

Source. Composition. Importance of the Milk Supply. Diseases from Milk. Necessity for Cleanliness. Safeguarding the Milk Supply. Our Duty to the Producer. Testing of Milk. Sterilization. Pasteurization. Certified Milk. Modified Milk.

Chapter XVIII— Milk Products 247-258

Condensed Milk. Evaporated Milk. Concentrated Milk. Milk Powders. Market Cream. Ice Cream. By-products of the Butter Industry. Skim Milk. Dried Casein. Milk Sugar. Buttermilk. Artificially Soured Milk. Cheese. Historical. Composition. Cheesemaking. Adulteration.

Chapter XIX — Preservation of Foods 259-270

Classification. Drying. Cooling. Sterilization and Exclusion of Air. Sugaring. Salting. Smoking. Use of Fats and Oils. Use of Spices. Alcohol. Use of Preservatives. Artificial Sweetening. Artificial Coloring.

Chapter XX — The Canning Industry 271-278

Historical. Process. Success of Canning. Meat Products. Containers. Advantages and Disadvantages of Glass. Advantages and Disadvantages of Tin. Adulteration.

Vlll CONTENTS

PAGE

Chapter XXI — Tea', Coffee and Cocoa , 279-300

Historical. Cultivation of the Tea Plant. Classification. Processes in Manufacture. Black Tea. Green Tea. Adulteration. Tea as a Beverage. General Rules for Tea-making. Composition of the Beverage. Coffee. Historical. The Coffee Plant. Cultivation. Processes in Manufacture. Adulteration. Coffee as a Beverage. Coffee Extracts. Cocoa. Historical. Cultivation. Processes in Manufacture. Chocolate. Adulteration. As a Beverage. Physiological Effect of Tea, Coffee and Cocoa.

Chapter- XXII — Spices and Condiments 301-313

Salt. Pepper. Mustard. Curry Powder. Vinegar. Spices. Uses. Spices as Preservatives. Cinnamon and Cassia. Cloves. Allspice. Nutmeg and Mace. Ginger. Adulteration. Vanilla and Lemon Extracts.

Bibliography 314-321

LIST OF ILLUSTRATIONS,

PAGE

Sedimentation Basins .25

Section of an English Filter Bed 26

Cleaning London Filter Beds 27

Interior of the East Albany, N. Y., Filter Plant 29

Distillation Apparatus 30

The Berkefeld Filter 31

Carbonic Acid Gas Generator 35

Longitudinal Section Through a Grain of Wheat 55

Section Through Part of a Grain of Wheat 56

Hand-stone 59

The Mortar and Pestle 60

Roughening Burr-Stones 62

Dust Collectors .* 65

Roller Mills 68

Middling Purifier 69

The Modern Sieve or Bolter 70

Bolting Reel 71

Bread Made from Entire Wheat, Patent and Graham Flours 76

Flour Sifter and Blender 99

Dough Mixing Machine 100

Dough Dividing Machine 101

Front View of Dough Divider 102

Machine for Wrapping Bread 103

Bread After Leaving Wrapping Machine 104

Baking Floor Showing Ovens 105

Flour Bolter, Blender and Automatic Weigher 106

Sweet Cracker Machine 106

Sheds and Board for Drying Tapioca 126

Steeped Corn Running to Crushers 128

Crushers 129

Separators 130

Hydraulic Presses for Oil 130

Dripping Boxes 132

Emptying Starch from Drip Boxes 133

Cane Mill, Philippines 139

Cane Crushers, Hawaii 140

Open Pan Evaporators, Philippines 141

Vacuum Pans, Hawaii 142

Multiple-effect Evaporating Apparatus 143

Vacuum Strike Pan ■ 144

Centrifugal Machines 145

The Wild Beet 146

ILLUSTRATIONS

PAGE

The Sugar Beet of To-day 147

Distribution of Beet Sugar Factories 148

The Circular Diffusion Battery 151

Filter Bags 154

Roller Mill for Grinding Barley Malt 174

Filter Presses for Clarifying Wort 175

Copper Boilers 1 76

Filter Presses for Clarifying Beer before Bottling 178

Early Experiment in Cream Separator 195

Improved DeLaval Cream Separator 196

Chilling Butterine 200

Beef Viscera Inspection 226

Lard Boiling 228

Cattle, Burnside Farm, N. Y 233

Bacterial Tests of Creamery Milk 237

Bacterial Tests of Creamery Milk 238

Pasteurization of Milk 243

Holding Tanks 243

Milk Coolers , 244

Milk Bottling Machine 244

Condensed Milk Industry 248

The Sausage Smoke House 266

Stock Boilers 273

Sterilizing Process 274

Can Closing Machines 277

The Tea Plant 280

Young Shoot of Tea Plant 282

Withering Tea Leaves ' 283

Rolling Tea Leaves 284

Coffee Bean 288

Coffee Cultivation and Industry in Brazil 290

Coffee Roasting Room 292

Pods and Leaves 295

Section of Cocoa Fruit 296

Grinding Room 298

Pepper Plantation near Singapore 303

Rolling Cinnamon Bark into Quills 307

Clove Tree of Zanzibar 309

Digging and Peeling Ginger in the Fields 310

Introduction

In regard to the production and manufacture of our food material, there is a prevalent ignorance among women to-day which is in marked contrast to the knowledge possessed on this subject by the old-fashioned housekeeper. The reason for this can readily be seen, for in the early days, and in fact until comparatively recent years, agriculture was very near the home and in the majority of cases the housewife herself was the manufacturer. The spinning-wheel now so highly prized as a memento of the olden times, testifies to the fact that our grandmothers knew full well how to manufacture the clothing for their families. A closer look at these same days will show that they knew equally well how to prepare many food products and materials needed for household work.

As civilization has advanced the tendency toward the massing together of our population in towns and cities has gradually changed greatly the home life of the people. Agriculture no longer is carried on in proximity to the home, and large commercial establishments remote from the household now do the work that at one time was the daily duty of the housewife. Many such examples can be found. In our later study of the history of milling, we will find that among all primitive people the woman was the miller, grinding each day the grain she was to make into bread; the preparation of the meal and breadmaking were practically one operation. Later on in the history of the human family, the making of meal and flour passed into the hands of the village miller, who ground the grain for the producers of his neighborhood, who in turn bought their sack of flour directly from him. As this business grew in size it gradually was moved further and further from the home, until the average housekeeper of to-day knows little of the mighty industry that is preparing the flour for her use. More and more each year, we find that the making of this flour into bread is in like manner passing into the hands of the modern manufacturer of bread. The old-time home-made loaf of bread is still found in isolated districts but seldom in city life. In the preparation of alcoholic beverages we again find this marked change. As late as our own colonial days, every housewife knew how to prepare beer and wines and her reputation as a homekeeper was judged as much by the beer that she could brew, as by the loaf of bread that she could bake. The curing of meat and fish by salting and smoking, the drying of fruits and vegetables are now known only to the housekeeper in isolated sections of our country, for the city woman must depend on the manufacturer's supply. Even the preservation of our food by canning is rapidly passing into the hands of the canning industry.

These marked changes in our food preparation have brought new types of foods on the market and have greatly increased the variety. To the modern housekeeper they have brought both advantages and disadvantages.

Advantages. — I. There has been a great lessening of household drudgery, giving an opportunity for broader interests and for more recreation than was known to our grandmothers.

II. In the majority of cases better products can be obtained for the processes used by the housekeeper were necessarily very crude. Manufacturers for financial reasons must give much study to their particular industry and new and better methods are constantly being sought. This has led to improved sanitary conditions and a standardizing of the quality of the product.

III. In recent years there has been a great extension of the open season; fresh fruits and vegetables are now quite common in the city markets the year round. The variety of food has been also increased by canning.

IV. Great improvements have taken place in the science of agriculture leading gradually to the raising not only of better products but to the increase in the area of production, of products which formerly were obtainable only from a limited section, such as oranges and other fruits, sugar from the beet and wines.

V. New and improved methods of food preservation have been largely studied, such as canning and the use of cold storage.

VI. The co-operation with scientists has led to protection against certain diseases, such as tuberculosis from meat and milk, typhoid from the oyster, trichina from pork, etc.

VII. Articles of food are now put up in better and more sanitary packages and better packing material is being used.

Disadvantages. — I. The cost of living has been greatly increased.

a. Foods may be roughly divided into permanent and perishable material. Among the permanent foods, which include sugar and flour the cost has decreased. The great advance in price of our food material is found entirely in the perishable foods. Such material is now being brought from a long distance, thus adding cost of freight and preservation during transportation. The many hands through which food material must pass also increases the cost.

b. The open market has led to expensive tastes. Luxuries look attractive and the cost is great where such products have been brought from a distance.

II. The women of our country represent about 90 per cent, of the retail buyers in food products. A lack of knowledge and many times of interest have led to great deception on the part of some manufacturers.

a. Until the Pure Food Law went into effect, there was a great amount of adulterated material put on the market and preservatives were most freely used.

b. The substitution of cheaper products with intent to deceive the purchaser was also a common practice. Butter substitutes were sold as butter, cottonseed oil as olive oil, apple jelly as currant, canned herring as sardines, potted veal for chicken, and the like.

c. Following these evils there gradually crept in the custom of printing misleading statements on the outside wrappers as to the effect and food value of the contents. Much advertising was done also giving these false impressions.

Had the modern housekeeper possessed the knowledge of her grandmother as to the production and manufacture of food material she was buying, manufacturers would not have found it advantageous to practice such frauds for so long a period.

The United States Government has for many years been studying and experimenting along these lines, and bulletins have been printed which can be procured free or at a very small cost, yet comparatively few housekeepers seek such information. This lack of knowledge and interest led the faculty of the School of Practical Arts, Columbia University, to introduce many years ago, into its domestic science course, a study of the manufacture of food material, hoping that a more extended knowledge of this subject would lead to greater interest and more intelligent buying on the part of the modern housekeeper.

In connection with the following course of lectures, excursions should be taken as frequently as possible to manufacturing establishments, where processes and methods can be studied and sanitary conditions noted. Wherever such excursions are not practical, illustrative material and demonstrations should be most freely used, accompanied whenever possible by the use of the stereopticon and moving picture slides.

Chapter I. Food Principles

Food principles, sometimes referred to as food stuffs, are types of chemical compounds differing in exact composition but of equal energy value. They are reducible to similar forms by the process of digestion.

Functions. — Food has two important functions : first, to supply tissue for the growth of the young child, and since life's processes are continually breaking down this body structure, to supply needed material for its repair; second, to furnish the organism with fuel which in combustion gives power to carry on life's activities ; the heat produced is utilized to maintain the temperature necessary to the organism.

Conservation of Energy. — Locked up in the resources of nature is a vast wealth of energy. Man has only to seize this energy and convert it into a form which he needs. Thus we find wood, coal, petroleum and natural gas being utilized to give heat and light. Should the energy be contained in a compound which can be finally assimilated by the human body he can accept it as a food.

Elements in Food. — Nature does not always give us these foods in a simple state ; most of them are quite complex in their nature. When analyzed, however, it has been found that even the complicated forms are composed of the most common elements, such as carbon, hydrogen, oxygen, nitrogen, with a small amount of sulphur, phosphorus, iron, calcium, etc.

Food Principles. — Although these elements may be differently combined, they can be divided into groups which are called the four food principles or food stuffs :

1. Carbohydrates composed of carbon, hydrogen and oxygen.

2. Fats composed of carbon, hydrogen and oxygen.

3. Protein composed of carbon, hydrogen, oxygen, nitrogen,

sulphur, generally phosphorus, sometimes iron, etc.

4. Mineral matter, . such as sodium, potassium, calcium, mag-

nesium, iron, sulphur, phosphorus, chlorine, and minute quantities of iodine, fluorine and silicon.

Water formerly regarded as a food principle, although having peculiar and intimate relations with the four accepted types, does not undergo metabolism and hence is excluded.

Examples of Each Group. — Among the carbohydrates we find well-known foods, such as starch, sugar, cereals and vegetables. Fats may appear in different forms, such as liquids, semi-solids and solids, represented by olive oil, butter and suet. Protein in its most concentrated form occurs in the white of egg, large amounts being also found in meat, fish, cheese, eggs and milk. Usually we look to animal life for our protein supply, although it occurs also in the vegetable kingdom, relatively large amounts being found in beans, cottonseed meal, peas, lentils and smaller amounts in wheat, maize and other cereals. The vegetable kingdom supplies mankind with most of his carbohydrate food, animal carbohydrate occurring only in such forms as milk-sugar, glycogen and glucose. Fat occurs frequently in both animal and vegetable life.

Function of Each Group. — Although all of the food principles have nutritive value each group has its own special function. This work may be: first, directly building tissue; second, giving energy and heat; third, making it possible for other groups to carry out their special function. The great work of building tissue and gradually repairing it as it wears away can be performed by protein and inorganic matter, water always assisting in this work. The other food principles cannot build tissue ; therefore protein, mineral matter and water are absolutely essential to life. None of the three is alone sufficient. The work of producing energy is done by all the food principles, although only in a very limited sense by mineral matter. Tissue Builders:

Protein.

Mineral matter.

Energy Producers :

Protein.

Carbohydrate.

Fat.

Protein alone is able to fulfil both of these functions of foods ; for this reason it is of vast importance in the diet. Without protein life is impossible for any length of time for the wear and tear on the tissue must be replaced. With protein assisted by water life can be maintained for some time. CARBOHYDRATES.

In order to obtain the necessary amount of heat and muscular energy it is necessary to supply the body with fuel. This work is done largely by the carbohydrates, a group containing carbon, hydrogen and oxygen. The hydrogen and oxygen occur in the same proportion as in water, and the carbon as six or some multiple of six in most of the forms utilized as human food. The carbohydrates owe their value as a fuel very largely to the carbon which on oxidation gives off much heat energy. They are found in a large variety of foods : flour, meal, cereals, sugar, starch, vegetables and fruits. Sometimes they appear in simple forms which can easily be made use of by the organism ; at other times so complicated is the molecule, that only after many chemical changes do they assume a form simple enough to pass through the membrane of the intestines. From the standpoint of nutrition the alimentary canal must be looked upon as outside the body, the lining of this canal being the outer coating of the body proper. All foods therefore must be reduced to chemical compounds which are capable of passing through the walls of the intestines before assimilation. The most important properties for assimilation are solubility and osmotic power. Those carbohydrates which cannot be reduced to forms having these properties cannot be utilized as food.

Classification. —

Monosaccharids or Simple Sugars, C 6 H 12 6 .

Glucose or grape sugar, formerly called dextrose.

Fructose or fruit sugar, formerly called levulose.

Galactose.

Disaccharids or Double Sugars, C 12 H 22 la .

Sucrose or sugar.

Maltose.

Lactose or milk sugar.

Polysaccharids or Complex Sugars, (C 6 H 10 O 5 )„ . Cellulose.

Starch.

Dextrin.

Glycogen.

Formation of Carbohydrates. — The monosaccharides or simple sugars are built up in the leaf of the plant by the absorption of the carbon dioxide and water of the atmosphere. With the assistance of the chlorophyll cells of green plants and the energy of the sun's rays, the following compounds are formed in the leaf :

Glucose, C 6 H 12 6 , is soluble and diffusible so it can pass from one part of the plant to another. When this material is to be stored as reserve food for the plant, water is withdrawn and starch, an insoluble and colloidal compound, is formed:

Occurence. — Glucose is an important simple sugar widely distributed in nature and is found to a great extent in the same plants as contain sucrose. Grapes contain about 20 per cent., hence the common name grape sugar. It occurs also in sweet corn and most of the garden vegetables and fruits. In animal life it occurs in small quantities in the blood, 0.1 per cent., where it is constantly being burned to produce energy. Where the body has more or less lost the power to burn glucose as in diabetes, it accumulates and is finally eliminated by the kidneys.

Fructose is usually found associated with glucose. It occurs in the juices of sweet fruits, the largest amount being found in honey.

Galactose is not found in nature. It occurs principally in the splitting of lactose or milk-sugar during the process of digestion.

Sucrose is the most important of the sugars as it is the ordinary crystallized sugar of commerce. 'It is found widely distributed in the vegetable kingdom in the fruit and juices of a variety of plants, many times occurring in relatively large amounts as in the pineapple, strawberry and carrot. Sucrose is extracted commercially from the sugar cane, the sugar beet, the sorghum cane, the date palm and the sugar maple.

Maltose never occurs in nature in large quantities. It is the carbohydrate which is formed from starch during the germination of seeds. As a commercial product it plays an important part in the brewing industry, in the so-called malted breakfast foods and in malted milk.

Lactose occurs in the milk of all mammals usually from 3 to 7 per cent, and is the most abundant of the animal carbohydrates.

Cellulose or crude fiber constitutes the framework of all vegetable tissue, so we find it widely distributed throughout the vegetable kingdom. It occurs in wood, linen, cotton, hemp, flax and paper. Much of our food, such as cereals, vegetables and fruit contain cellulose, but as it cannot be made soluble in the organism it has no food value. Other forms of life can utilize it, however, and we find it serving as food for insects and bacteria.

Starch as it is found in nature is also insoluble and indiffusible, hut here we find a carbohydrate which can be changed to a simpler form within the alimentary canal. It is found largely in vegetables amd cereals where it is stored as food for the plant.

Dextrin or, as it is erroneously called gum, is formed from starch by the process of hydrolysis. In nature it occurs in germinating cereals.

Glycogen, often spoken of as the animal starch, although it more closely resembles dextrin, is found to the largest extent in shell-fish, especially the scallop. It is also abundant in the muscle and liver of both higher and lower animals, where it is stored and ultimately utilized as a source of muscular energy. In plants glycogen has a restricted distribution, although it occurs abundantly in certain fungi to the extent of 30 per cent, of the dry weight.

Important Properties. — Among the most important properties of the carbohydrates are found solubility, diffusibility, hydrolysis, crystallization and action on polarized light.

IO FOOD INDUSTRIES

Hydrolysis. — This important property occurs repeatedly in the changing of complicated forms of food material, to such simple forms that they can be utilized by the organism. It has been defined by Alexander Smith as "A double decomposition involving water" and by other well-known chemists as "A simplification with absorption of water." Changes taking place during hydrolysis are always brought about by catalytic agents. These agents may be heat, dilute acid, finely divided metal, enzyme action, etc. The action always takes place in the presence of water, both the water molecule and the complex carbohydrate molecule breaking down to form a new carbohydrate molecule in which the hydrogen and oxygen appear in the proportion as in water.

2C 6 H 10 O 5 + H 2 ^ C 12 H 22 O n , Starch Maltose

Maltose Glucose

Sucrose is a double sugar. When it breaks down under the

influence of a catalytic agent it yields two simple sugars as

A special name has been given to these two molecules, glucose and fructose. They are called invert sugar. This name has been given to them on account of their peculiar behavior toward polarized light. Before hydrolysis a sugar solution will rotate the plane of polarized light to the right, after hydrolysis to the left, hence the name invert sugar and the term inversion.

Hydrolysis also occurs in the digestion of fats and proteins.

FATS.

Composition. — True fats are composed of the elements carbon, hydrogen and oxygen. Little was known of how these elements were combined in the formation of fats, until the investigation by Chevreul in the early part of the nineteenth century. He discovered that they were essentially salt-like bodies formed together with water by the combination of an acid and a base. With the exception of some of the waxes the base is always the same, the triatomic alcohol glycerin, C 3 H 5 (OH) 3 . The acid

FOOD INDUSTRIES II

usually belongs to a series termed fatty acids and varies according to the fat. The three most common fatty acids are oleic, palmitic and stearic acid. Unless a fat or oil contains both glycerin and a fatty acid, it is not a true fat.

C 3 H 5 (OH) 3 + 3 C n H S3 COOH ^ C 3 H 5 (C 18 H 33 2 ) 3 + 3 H 2 0, Glycerin Oleic acid. Olein Water

C s H 5 (OH) 3 + 3 C ]5 H 31 COOH ^ C 3 H 5 (C 16 H 31 2 ) 3 + 3H 2 0, Glycerin Palmitic acid Palmitin Water

C 3 H 5 (OH) 3 + 3 C 17 H 35 COOH ^ C 3 H 5 (C 18 H 35 2 )a + 3H 2 0. Glycerin Stearic acid Stearin Water