Library of Congress Catalog Card Number: 97-73710 International Standard Book Number: 0-913250-94-5 ©1997 by the American Association of Cereal Chemists, Inc. All rights reserved. No part of this book may be reproduced in any form, including photocopy, microfilm, information storage and retrieval system, computer database or software, or by any means, including electronic or mechanical, without written permission from the publisher. Reference in this publication to a trademark, proprietary product, or company name is intended for explicit description only and does not imply approval or recommendation of the product to the exclusion of others that may be suitable. Printed in the United States of America on acid-free paper American Association of Cereal Chemists 3340 Pilot Knob Road St. Paul, Minnesota 55121-2097, USA About the Eagan Press Handbook Series The Eagan Press Handbook series was developed for food industry practitioners. It offers a practical approach to understanding the basics of food ingredients, applications, and processes—whether the reader is a research chemist wanting practical information compiled in a single source or a purchasing agent trying to understand product specifications. The handbook series is designed to reach a broad read- ership; the books are not limited to a single product category but rather serve professionals in all seg- ments of the food processing industry and their allied suppliers. In developing this series, Eagan Press recognized the need to fill the gap between the highly frag- mented, theoretical, and often not readily available information in the scientific literature and the prod- uct-specific information available from suppliers. It enlisted experts in specific areas to contribute their expertise to the development and fruition of this series. The content of the books has been prepared in a rigorous manner, including substantial peer review and editing, and is presented in a user friendly format with definitions of terms, examples, illustrations, and trouble-shooting tips. The result is a set of practical guides containing information useful to those involved in product development, production, testing, ingredient purchasing, engineering, and market- ing aspects of the food industry. Acknowledgment of Sponsor for Dairy-Based Ingredients Eagan Press would like to thank the following company for its financial support of this handbook: Davisco Foods International Eden Prairie, Minnesota 800-757-7611 Eagan Press has designed this handbook series as practical guides serving the interests of the food industry as a whole rather than the individual interests of any single company. Nonetheless, corporate sponsorship has allowed these books to be more affordable for a wide audience. Acknowledgments The author thanks the following individuals for assisting, reviewing, and providing valuable counsel in the preparation of this book: Gint Behrens, Land O’Lakes, Inc., Arden Hills, MN Rulon Chappell, Chappell International, Inc., St. Paul, MN Staff at Dairy Management Inc., Rosemont, IL William Davidson, General Mills Inc., Minneapolis, MN Todd Gusek, Cargill Inc., Minnetonka, MN Loretta Kolberg, General Mills Inc., Minneapolis, MN James Langler, General Mills Inc., Minneapolis, MN Karen Schmidt, Kansas State University, Manhattan, KS Glenn Van Hulle, General Mills Inc., Minneapolis, MN Joseph Warthesen, University of Minnesota, St. Paul, MN Contents 1. Properties of Milk and Its Components • 1 Milk Composition Constituents of Milk: major constituents • minor and trace constituents Physical Properties of Milk: color • flavor • density and specific gravity • surface tension • foaming • viscosity • specific heat • electrical conductivity • freezing point • boiling point • refractivity 2. Basic Milk Processing • 11 Raw Milk Handling and Storage Separation Standardization: fat standardization • standardization of fat and solids-not-fat Pasteurization Homogenization Packaging and Storage 3. Production and Specifications of Milk Concentrates • 23 Concentrated Milk Products: condensed products • dry milk products Whey Products and Lactose: processing techniques • whey products • lactose Milkfat Concentrates: cream • butter and its products 4. Processing and Specifications of Dairy Foods • 41 Cheese and Cheese Products: natural cheeses • process cheese products • other Fermented Milks Ice Cream and Frozen Desserts: formulation of ice cream • soft frozen dairy products 5. Baked Products • 57 Butter in Baked Products: functions of butter • handling of butter in bakeries Hard Wheat Products: pastry and laminated doughs • bread and biscuits Soft Wheat Products: cakes • crackers • other products Role of Dairy Ingredients in Fat Reduction of Baked Foods Troubleshooting v 6. Chocolate and Confectionery Products • 69 Chocolate Products: dairy-based ingredients • manufacturing considerations Confections: dairy-based ingredients • manufacturing considerations New Opportunities in Chocolate and Confections for Dairy-Based Ingredients Troubleshooting 7. Sauces, Dressings, and Dairy Desserts • 79 Cheese Sauces/Dressings:manufacture • quality evaluation Dressings and Dips:dairy salad dressings • sour-cream-based dips Puddings Troubleshooting 8. Snack Foods, Meats, and Other Applications • 89 Snack Foods: collets • chip production • cheese seasonings Meat Products: functional properties of dairy-based ingredients • processing considerations Other Applications: infant formulas • functional foods • dairy biologics • probiotics and prebiotics Troubleshooting 9. Nutrition and Labeling • 103 Nutrients in Dairy Products: vitamins and minerals • protein quality • milkfat • nutritional concerns • milk allergy Food Labeling 10. Regulatory and Safety Aspects • 111 Regulation by the Food and Drug Administration: the Pasteurized Milk Ordinance • standards of identity Analytical Tests Microbiological Safety and Sanitary Practices: good manufacturing practices • hazard analysis and critical control points Appendix A. Origin and Description of Some Off-Flavors in Milk • 119 Appendix B. Typical Composition of Dairy Ingredients • 121 Appendix C. Typical Specifications for Milk Concentrates • 123 Appendix D. Processing Guidelines • 127 Glossary • 131 Index • 135 vi CHAPTER 1 Properties of Milk and Its Components Milk and dairy-based ingredients are used as components of many In This Chapter: food products. Their contributions consist of unique flavor, desirable texture, excellent nutritive value, and a widely accepted “natural” Milk Composition image. In many instances, the success of the product in the market- Constituents of Milk place is significantly enhanced by incorporation of traditional func- Major Constituents tional ingredients familiar to the consumer. Thus, dairy ingredients Minor and Trace provide a consumer-friendly label on packaged foods. Constituents Dairy ingredients contribute a number of characteristics critical to Physical Properties a food product. These include the emulsifying and stabilizing ability of Milk of caseinates, the gelling properties of whey protein concentrates and Color isolates, the water-absorption capacity of high-heat nonfat dry milk, Flavor and the browning of lactose during heat processing. Furthermore, Density and Specific the crystallization characteristics of lactose and the hydrolytic activ- Gravity ity of the enzyme lactase are important in confectionery and frozen Surface Tension products. In addition, butter flavor carryover can be achieved with Foaming enzyme-modified butterfat and various cheese flavors imparted by Viscosity enzyme-modified cheeses. Therefore, a food developer can select an Specific Heat appropriate dairy-based ingredient to create certain desirable attrib- Electrical Conductivity utes in foods. An understanding of the functional properties of dairy Freezing Point ingredients allows food technologists to utilize their potential con- Boiling Point tribution to product characteristics to meet consumer expectations. Refractivity Milk Composition Caseinates—Compounds Milk may be defined various ways. Chemically speaking, milk is a derived by the interaction of complex fluid in which more than 100 separate chemical com- alkali with casein, the major pounds have been found. Its major components are water, fat, lac- milk protein. tose, casein, whey proteins, and minerals (or ash) in amounts vary- ing with the milk of various species of animals. However, for any Whey—The watery liquid remaining after the curd is given species, the range of values for the constituents of milk is fair- formed in the manufacture of ly constant. cheese and fermented or acidi- From a physiological standpoint, milk is the secretion of the nor- fied dairy products. mally functioning mammary gland of the females of all mammals, which is produced for some time following parturition for the nour- Lactose—Milk sugar, com- ishment of the young of the species during the initial period of posed of glucose and galactose. growth. Lactase—The enzyme that In terms of physical chemistry, milk is an opaque, whitish fluid of splits lactose (milk sugar) into multidisperse phases. The true solution contains lactose, vitamins, glucose and galactose. 1 2 / CHAPTER ONE Ash—The residue left when a acids, enzymes, and some inorganic salts. The colloidal phase con- substance is incinerated at a tains casein, calcium phosphate, and globular proteins. Fat exists in very high temperature for the form of an oil-in-water type of emulsion, with fat globules vary- analysis. ing from 0.1 to 22 µm in diameter. As a food ingredient or consumed by itself, milk provides an excel- Parturition—The act or lent nutritional profile in the human diet. Nutrition experts consid- process of giving birth. er milk an exceptionally complete food because it contains signifi- cant levels of required nutrients such as protein, fat, carbohydrates, minerals, and several vitamins. Low-fat and nonfat milks are increas- Colloidal phase—The portion of milk containing dispersed ingly popular in fat-reduced and fat-free food formulations. particles ranging in diameter Worldwide, milk of the cow is by far of more commercial importance from 10–5to 10–7cm. than milk of any other mammal. In the United States, the term “milk” legally refers to cow’s milk. Milk from other species is labeled to indi- Emulsion—A homogeneous cate the type: sheep’s milk, goat’s milk, etc. Milk is the whole, clean dispersion of two dissimilar lacteal secretion of one or more healthy cows, properly fed and kept, immiscible liquid phases. If oil excluding that obtained within 15 days before calving and three to five is dispersed in water, it is an days after. Colostrum, the milk secreted immediately after giving birth, oil-in-water (O/W) emulsion. If is not considered milk from a legal standpoint. The U.S. Public Health water is dispersed in oil, it is a Service’s definition of Grade A milk is “the lacteal secretion practically water-in-oil (W/O) emulsion. free from colostrum, obtained by complete milking of one or more healthy cows, which contains not less than 8.25% milk solids-not-fat Low-fat milk—Milk containing (MSNF) and not less than 3.25% milkfat.” at least 8.25% solids-not-fat and with fat reduced to deliver not more than 3 g of milkfat Constituents of Milk per serving of 8 fl oz. Also termed light milk. Milk is composed of water, milkfat, and MSNF. The MSNF consists of protein, lactose, and minerals. These solids are also referred to as skim solids, or serum solids. The term total solids refers to the serum Nonfat milk—Milk containing at least 8.25% solids-not-fat solids plus the milkfat. and with fat reduced to deliver The major components of commercial raw milk (1–3) are illustrat- not more than 0.5 g of milkfat ed in Figure 1-1. On a dry basis, the composition of milk solids is per serving of 8 fl oz. Also shown in Figure 1-2. The composition of the MSNF portion of milk termed fat-freeor skim milk. is given in Figure 1-3. Colostrum—The first milk MAJOR CONSTITUENTS secreted by an animal just before and after the birth of its The major constituents of milk vary more widely in individual young. cow’s milk than in pooled market milk. Factors affecting the milk such as breed of cow, intervals of milking, stages of milking, differ- Oestrum/Estrus—Period of sexual receptivity (heat) in Casein, female mammals. 2.8% Fat, 3.7% Protein, 3.4% Milk solids, Casein micelles—Large col- 12.6% Whey protein, Milk 0.6% loidal particles that are com- solids-not-fat, Lactose, plexes of protein and salt ions, Milk 8.9% 4.8% principally calcium and phos- phorus. Water, Minerals, 87.4% 0.7% Fig. 1-1.Gross composition of milk, showing major constituents. PROPERTIES OF MILK \ 3 ent quarters of udder, lactation period, season, feed, nutritional Ash level, environmental temperature, health status, age, weather, 5.56% Fat Lactose oestrum, gestation period, and exercise are known to cause variations 29.36% 38.1% in fat, protein, lactose, and mineral levels in milk derived from indi- vidual cows (4,5). In general, these variations tend to average out but display an interesting seasonal pattern in commercial milk used by food processors, which may have an important impact on properties of the finished products. An approximately 10% variation in fat and protein is observed in milk received in July and August (lowest level) compared to that received in October and November (highest level). Casein Whey Protein Variations in protein and fat during the year affect yogurt and cheese 22.22% 4.76% manufacture and whey protein production. For example, appropri- ate adjustments, such as fortification with additional nonfat milk Fig. 1-2. Composition of milk solids, are necessary in yogurt production to ensure uniform viscos- solids of whole milk. ity throughout the year. Milk proteins. Caseins make up approximately 80% of milk pro- teins. The remaining proteins are classified as whey proteins. Milk proteins and their concentration in milk are shown in Table 1-1. TABLE 1-1.Milk Proteinsa Concentration Whey Type Nomenclature (g/L of milk) Protein Casein 7.53% Lactose Casein 24–28 31.18% 52.15% α -Casein 12–15 s1 α -Casein 3–4 s2 β-Casein 9–11 κ-Casein 3–4 γ-Casein 1–2 Whey protein 5–7 β-Lactoglobulin 2–4 Fat α-Lactalbumin 1–1.5 1.08% Ash Bovine serum albumin 0.1–0.4 8.06% Immunoglobulins 0.6–1.0 Proteose peptones 0.6–1.8 Fig. 1-3.Composition of non- fat solids of skim milk. a From: Functional Properties of MilkProteins, by O. Robin, S. Turgeon, and P. Paquin, in: Dairy Science and Technology Handbook, Vol. 1, Y. H. Hui, Ed.  1993 by VCH Publishers. Used by permission of John Wiley & Sons, Inc. Besides having a biological and nutritional role, caseins and caseinates are important because of their structure, charge, and phys- ical properties. Caseins become insoluble when the milk is acidified and the pH is reduced to 4.6, while the whey proteins remain in solution. Caseins exist in milk as particles called micelles, which are made up of calcium phosphate and casein complexes. The micelles are spherical particles varying in size from 50 to 200 nm and con- taining thousands of protein molecules. Caseins are further divided into α , α , β, and κfractions. A γ-fraction is derived from the break- s1 s1 down of β-casein by inherent proteolytic enzymes of milk. Each of 4 / CHAPTER ONE Rennin—A milk coagulatory the casein fractions exhibits distinct chemical properties. For exam- enzyme found in the gastric ple, α and α caseins have eight and 10–13 phosphoserine units, s1 s2 juice of the fourth stomach of respectively. β-Casein has five phosphoserine units. All the casein calves. fractions except κ-casein are precipitated by calcium, whereas κ- casein, which contains one phosphoserine unit, is not calcium-sen- Serum phase—The watery por- sitive. Only κ-casein contains a carbohydrate moiety. Calcium (30 tion of a fluid; the portion of mM) and phosphate (20 mM) are complexed with α , α , and β- s1 s2 milk without fat globules and caseins, whereas κ-casein stabilizes the colloidal particles (micelles) casein micelles. by surface binding. During cheesemaking, the stabilizing κ-casein is cleaved by the enzyme rennin, resulting in destabilization of the Lipids—A class of compounds micelle and subsequent curd formation. found in nature that are soluble Whey proteins are located in solution in the serum phase of milk in organic solvents such as along with minor proteins and enzymes, including lactoperoxidase, ether or hexane. Examples are lactotransferrin, lysozyme, glycoprotein, serum transferrin, and triacylglycerols, cholesterol, and vitamin A. degradation products derived from casein. Caseins and whey proteins are distinguishable from each other by their physical and chemical characteristics (Table 1-2). Caseins have a distinct, disordered molecular structure that lacks stabilizing disul- fide bridges. This characteristic structure makes the casein fraction precipitate in acidic conditions as well as in the presence of di- and polyvalent ions of various salts. Casein molecules exist naturally in an open and extended state. Therefore, heat has little or no effect on them. However, severe heat treatment results in detachment of phosphate groups as well as formation of brown pigments by inter- action with milk sugar (the Maillard reaction). Whey proteins have a relatively more ordered molecular structure, which contains disulfide linkages. Accordingly, they are not vulner- able to precipitation under acidic conditions or by polyvalent ions. Like other globular proteins, they can be heat-denatured, resulting in gel formation. β-Lactoglobulin complexes with κ-casein in milk subjected to rigorous heat treatment. In food systems, milk proteins contribute to properties of the final product. Table 1-3 summarizes the major functional characteristics of milk proteins. Milkfat. The fat in milk occurs in microscopic globules in an oil-in- water type of emulsion. The globules vary in size from 0.1 to 22 µm in diameter. The lipid content of milkfat is 97–98% triacylglycerols, 0.2–1% phospholipids, 0.2–0.4% sterols, and traces of fatty acids, as well as vitamins A, D, E, and K. Milkfat is made up of 65% saturated, TABLE 1-2.Major Physical and Chemical Differences in Milk Proteins Caseins Whey Proteins Strong hydrophobic regions Both hydrophobic and hydrophilic regions Little cysteine content Both cysteine and cystine present Random coil structure Globular structure with helical contents Heat stable Easily heat denatured and insolubilized Precipitate in acidic conditions and insoluble at pH 4.6 Stable in mild acidic environment Precipitated by di- and polyvalent ions