Dairy chemistry textbooks are extensively accessible, with numerous authors being of Western or Indian origin. What purpose does another textbook serve, given this abundance of resources? I have grappled with this question for an extensive period of time before embarking on this project. Traditional Indian milk products are not commonly covered in Western textbooks, despite their significance for Indian students. The majority of books do not address the chemistry of milk and milk products, including the chemistry of conventional milk products, which are typically overlooked. Consequently, students studying dairy chemistry have been compelled to rely on a variety of textbooks. To address this deficiency, I have endeavored to include the fundamentals of milk chemistry, the chemistry of milk products, including traditional Indian milk products, and the sophisticated analytical methods necessary for their analysis.
Each chapter concludes with a list of reference books, which while not covering every detail, will serve as a useful quick reference for students studying dairy chemistry.
Dairy chemistry textbooks are widely available, with many of the authors being Western or Indian. What use does another text book serve, then? I have been putting off this question for a long time before starting this project. The chemistry of traditional Indian milk products is not often covered in Western textbooks, despite the fact that knowledge of this subject is crucial for Indian students. The chemistry of milk and milk products, including the chemistry of traditional milk products are not usually available under one cover. As a result, the students’ study of dairy chemistry has seen them forced to rely on various text books. I’ve made an effort to include the fundamentals of milk chemistry, the chemistry of milk products, including the chemistry of traditional milk products from India, and the sophisticated analytical ideas needed to analyse them. It provides a thorough synopsis of the chemistry of every type of milk product. Both the knowledge development during undergraduate study and the preparation for the postgraduate entrance exam will be greatly benefited by the discussions. The end of each chapter includes a list of a few reference books. Although they don’t cover every detail, these will be useful to students as a quick reference when studying dairy chemistry. My reverend teachers, Prof. A.K. Bandyopadhyay and Prof. P.K. Ghatak, have shown me the way to write volumes of this kind, and for that I am grateful to them. I would especially like to thank Dr. Soma Maji, an Assistant Professor in the dairy technology department at Centurion University of Technology and Management in Odisha, for her invaluable assistance in a number of ways while I worked on this book. I am thankful to my postgraduate students, Payel Karmakar, Ankita Pandit, Chandrakanta Sen, Trisha Roy, Pratigya Pradhan, and Alisha Chhetri, for their assistance in preparing this manuscript. I humbly ask for your forgiveness because I refuse to take on the nearly impossible task of remembering the names of every other colleague who has assisted me, either directly or indirectly, in publishing this book. I am obliged to NIPA Genx Electronic Resources and Solutions P.Ltd, New Delhi, for providing me the opportunity to publish this book volume. I also want to thank NIPA’s very talented and productive publishing team.
Introduction The mammary glands of female mammals secrete milk, a necessary food that is liquid and meets the newborn’s nutritional needs. All mammals consider milk to be a complete food for their newborns. It is considered a necessary food for humans and can be consumed as a product or as liquid milk. It contains almost all essential nutrients except iron, which is very low in milk. In essence, milk is an emulsion of protein and fat in water, supplemented with carbohydrates, vitamins, and minerals. Definition of Milk • Milk is a complex biological fluid that differs from species to species in both composition and physical properties. It is the full lacteal secretion of a mammary gland that is obtained by milking mammals for a minimum of 72 h after calving or until the milk is free from colostrum. • FSSAI defines milk as the normal mammary secretion derived from the complete milking of healthy milch animals. It should be free from colostrum. From a chemical perspective, milk is a dynamically balanced mixture that comes in different forms such as emulsion, colloidal suspension, and true solution. It also contains varying amounts of proteins, fats, carbohydrates, salts, and water. Gross Composition of Milk Milk composition varies among different mammals. The average chemical composition of milk in various species is given in Table 1. Buffalo milk and sheep milk contain higher amounts of fat, while human milk comparatively has the highest lactose content. Human milk has lower protein content as compared to milk of other species.
Bovine milk contains an average of 3.5% protein. The concentration of protein changes significantly during lactation. The first few days of lactation exhibit the main change in protein concentration. The main changes occur in whey protein fraction. Distribution of Protein in Milk 80% casein and 20% whey protein (β lactoglobulin- 10%, α- lactalbumin- 5%, serum albumin, and immunoglobulin- 5%). Fractionation of Milk Proteins Fractionation of milk protein is mainly done by acidification at pH 4.6 around 30 °C. Almost 80% of the bovine milk protein precipitates at pH4.6, and this fraction yielded by precipitation is called casein. The remaining soluble part of the protein is referred to as whey protein/serum protein/ non- casein protein. Wide variation is observed in the casein- whey protein ratio in different types of milk(protein synthesis is independent of animal diet) Significant Difference Between Casein and Whey Protein 1. Casein precipitates at pH 4.6 but does not precipitate whey protein at that pH. This property of milk protein is commercially exploited for the preparation of industrial casein and certain varieties of cheese. 2. Chymosin or other proteolytic enzymes produce specific changes in casein resulting in coagulation in the presence of calcium. Whey protein does not undergo this type of coagulation. 3. Casein is very stable to high temperatures. They can withstand heating up to 140 °C for 20 minutes but whey protein is relatively heat labile. They are completely denatured by heating at 90 °C for 10 min. 4. Casein is a phosphoprotein containing an average of 0.85% phosphorous while whey protein does not contain any phosphorous. The phosphate of casein is an important contributor to remarkably high heat stability and calcium- induced coagulation of rennet- altered casein. 5. Casein contains very low sulfur (0.8%) whereas whey protein is relatively rich in sulfur (1%). The principle casein contains only methionine but whey protein contains a significant amount of cystine, cysteine, and methionine. These sulfur- containing amino acids are responsible for many changes in milk on heating. 6. Casein is synthesized only in the mammary gland and no other sources in nature. Some of the whey proteins β lactoglobulin, and α- lactalbumin are synthesized in the mammary gland but bovine serum albumin and immunoglobulin are not synthesized in the mammary gland but derived from blood. 7. The whey protein is dispersed in solution and has a simple quaternary structure. Casein has a complex quaternary structure and exists in milk as large colloidal aggregates.
Carbohydrates are polyhydroxy derivatives of aldehydes or ketones and undergo all the organic reactions common to the carbonyl groups and hydroxyl groups. The principal milk carbohydrate is lactose. It is a disaccharide. Hydrolysis of lactose with enzyme β-galactosidase yields glucose and galactose. Lactose is the major carbohydrate present in all types of milk. The first record of isolation of lactose was in 1663, by Bartolettus by evaporation of whey. Milk contains only trace amounts of other sugars, including glucose, fructose, glucosamine, galactosamine, neuraminic acid, and neutral and acidic oligosaccharides. Lactose plays a significant role in milk and milk products that are • It plays a major role in the production of fermented dairy products. • It contributes to the nutritive value of milk and milk products • It affects the texture of certain concentrated and frozen products; • It is involved in heat-induced changes in the color and flavor of highly heated milk products. Status of Lactose Lactose content varies extensively in the milk of different species. Breed of animal, individuality factors, udder infection, and especially the stage of lactation regulates the lactose content in milk. The lactose concentration in milk decreases gradually and significantly during lactation; this behavior contrasts with the lactational trends for lipids and proteins, which, after a decrease during early lactation, increase significantly during the second half of lactation. Lactose synthesis is hampered during mastitis. Lactose, along with sodium, potassium, and chloride ions, plays the principal role in controlling the osmotic pressure of the mammary system. Thus, any change in lactose content is compensated by a change in the soluble salt constituents. The osmotic relationship between lactose and soluble salts during the secretion of milk partly explains the presence of high lactose in milk with a reduced ash content and vice versa (Table 1).
Milk lipids or milk fats exist as an emulsion of small spherical droplets called milk fat globules. These globules are very small in size but very large in number. The diameter of the milk fat globules ranges between 0.1 and 22 µm and the number varies between 1.5 and 3.0 billion globules/mL. The average size of milk fat globules ranges from 2 to 5 µm. The average fat globule size in cow and buffalo milk are 3.4 and 4.5 µm, respectively. The surface of the milk fat globules is coated with an adsorbed layer of material known as the milk fat globule membrane (MFGM). MFGM contains phospholipids and proteins in a complex form. MFGM has two main functions (a) fat globule stabilization and (b) preservation of the fat globule’s identity. General Composition Triacylglycerols (triglycerides) represent 97–98% of the total lipids in the milk of most species. The diglycerides probably represent incompletely synthesized lipids in most cases. Although phospholipids represent less than 1% of total lipids, they play an important role in being present mainly in the MFGM and other membranous material in milk. The principal phospholipids are phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin. Trace amounts of other polar lipids, including ceramides, cerebrosides, and gangliosides, are also present. Phospholipids represent a considerable percentage of the total lipid of buttermilk and skim milk reflecting the presence of proportionately larger amounts of membrane material in these products.
The salts of the milk include those constituents that are present as ions or in equilibrium with ions. The main salts of milk are phosphates, citrates, chlorides, sulfates, carbonates, and bicarbonates of sodium, potassium, calcium, and magnesium. Approximately 20 other elements are found in milk in trace quantities including copper, iron, lead, boron, manganese, zinc, iodine, etc. These ions are more or less associated with themselves and with proteins. Some metals act as catalysts in the oxidation of milk fat leading to oxidative rancidity and certain metals like Ca, P, Mg, Mo, Co, Fe, etc. are components of metalloproteins such as lactoferrin, lactoperoxidase, xanthine oxidase, and parts of phospholipids. Distribution of Salts Between Casein Micelles and Serum The phosphorus is present as orthophosphate, but part of it is bound to organic components like serine and threonine residues of casein, molecules of hexoses and glycerol, phospholipids, etc. Phosphorus is also found in the hydroxyapatite structure of the colloidal calcium phosphate in the micellar structure of casein. The sulfur content of milk is about 0.36 g/kg, but most of it is in the amino acid residues methionine and cysteine of the proteins. About 10% is present as inorganic sulfate. Physical Equilibria Among Salts Milk contains several elements but all of them are not entirely in a soluble state. Some minerals exist in colloidal and ionic states at the normal pH of milk. The compounds that are in soluble condition play an important role in keeping various milk constituents in stable condition. A balance exists between the components that are in a soluble state and those which are in colloidal state.
Types of Enazymes in milk 1. Endogenous and 2. Exogenous. Three sources of enzyme in milk: 1. The blood via defective mammary cells. 2. Secretory cell cytoplasm. Some of which are occasionally entrapped with fat globules by the encircling MFGM. 3. The outer layer of MFGM is probably the principal source of endogenous enzymes in milk. The outer layer of MFGM is derived from the apical membrane of the secretory cell which in turn originates from the Golgi membrane and acts as the principal source of enzyme in milk. General Characteristics of Milk Enzymes 1. Deteriorative character e.g. lipase (commercially most important enzyme in milk), proteinase, acid phosphatase, xanthine oxidase. 2. Preservative enzymes. e.g. superoxide dismutase, sulfhydryl oxidase. 3. As an indicator of the thermal treatment history of milk. Related enzymes are alkaline phosphatase, ϒ glutamyl transpeptidase, and lactoperoxidase. 4. Mastitis infection indicator. Related enzymes are catalase, n-Acetyl-β D-glucosaminidase, and acid phosphatase. 5. Antimicrobial activity. 6. Commercial source of ribonuclease and lactoperoxidase Common Milk Enzymes and their Role in Dairy Industry
Chemistry of Creaming After being drawn from animals, normal milk will form a cream layer on standing. Because of the difference in density between fat globules (920 kg m−3 at room temperature) and milk plasma (density 1030 kg m−3), the granules tend to rise. This causes creaming, which we often want to prevent and it enables milk to be separated into cream and skim milk. Creaming is much enhanced when the globules have been aggregated into flocculates, clusters, or granules. Cream Ripening This unit operation serves as an intensive preparation of the cream for the churning process. It is divided into two categories. 1. Physical ripening; 2. biochemical ripening The following criteria are influenced by the cream ripening: • Consistency, firmness, and spreadability of butter. • Basic water content of butter during the manufacturing process (bound water in butter, which cannot be removed by any mechanical treatment). • Buttermilk fat content, which has to be minimized. The melting and solidification behavior of fat depends on the attached fatty acid, which indicate the hardness of the butterfat. Natural hardness is caused mainly by seasonal feeding of the milk animals. Winter feed with a great deal of dry feed or roughage yields a hard butterfat with a high percentage of saturated and short-chain fatty acids and few double bonds in the fat molecules. Summer feeding (green grass) results in fat with longer chains and a higher percentage of unsaturated fatty acids with many double bonds. We therefore distinguish between summer fat and winter fat or summer cream and winter cream.
Cheese is made from milk, with the addition of cream, buttermilk, and/or whey. This basic raw material is also called cheese milk. Cheese consists mainly of casein (the major protein of milk), other milk proteins, fat, other milk components, and a certain percentage of water, which is bound. Proteins are precipitated by enzymes and/or acidification as well as heat and are separated by suitable processes from the aqueous phase. (whey, serum). Cheese is most often molded, pressed, and salted and has fungal and bacterial culture additions. colorants, herbs, spices, and other non-dairy ingredients are also added to the cheese. It is consumed either fresh or at different stages of ripening. Worldwide, there are more than 2000 types of cheese, sometimes made by very different manufacturing processes. A classification can be based on several aspects and is done in different countries according to different criteria. A general classification can be made for three major groups: a. Rennet or natural cheese: manufactured straight from milk by using proteolytic enzymes (rennet) and acid, with a more or less pronounced ripening process. b. Fresh cheese or non-ripened Cheese: Quarg, fresh cheese, and white cheese are examples. Its manufacturing process is similar to that of rennet cheese manufacturing, but it has a high degree of acidity and is not subjected to a proteolytic ripening process. c. Long-life cheese (processed cheese): it is more often made from rennet cheese and is textured by thermal treatment and made shelf-stable.
Commercially, one of the most significant milk products is ice cream. It is a frozen product which is usually made from milk or cream that has been f lavored with fruits like peaches or strawberries, and spices like vanilla or cocoa, or with sugar or a substitute. Stabilizers are sometimes combined with food coloring. Ice cream mix typically contains 10.0% milk fat, 11.0% solids not-fat, 14.0% added sugar, and 0.3% additives like an emulsifier, stabilizer, f lavor, and color substances. Standard of Ice Cream According to FSSA (2006), ice cream, kulfi, chocolate ice cream or softy ice cream means the product obtained by freezing pasteurized milk prepared from milk and/or other products derived from milk with the addition of sweetening agents and fruit products, egg products, coffee, cocoa, ginger, and nuts. It may also contain chocolate, and bakery products such as cake or cookies as a separate layer and/or coating. It may be frozen hard or frozen to a soft consistency. It shall be free from artificial sweeteners. It shall have a pleasant taste and smell free from flavor and rancidity. It may contain food additives. It shall conform to the microbiological requirements as given in FSSA (2006).
Concentrated milk products are obtained through partial removal of water which increases the dry matter content of milk. The increase in dry matter content in concentrated milk is proportional to the degree of concentration. The milk concentrate may be prepared from either full-cream whole milk or fat-free skim milk. Depending on the nature of raw material and other non-milk additives concentrated milks are classified into four broad categories. 1. Sweetened condensed milk 2. Evaporated milk or unsweetened condensed milk 3. Sterile milk concentrate 4. Reconstituted concentrated milk Sweetened Condensed Milk One of the earliest dairy products to be produced industrially is sweetened condensed milk. According to FSSA (2006), sweetened condensed milk is the product obtained by partial removal of water from the milk of cow/buffalo with the addition of sugar or a combination of sucrose with other sugars or by any other process that leads to a product of the same composition and characteristics. The fat and/or protein content of the milk may be adjusted by the addition and/or withdrawal of milk constituents in such a way as not to alter the whey protein to casein ratio of the milk being adjusted. It shall have a pleasant taste and flavor and be free from off-flavor and rancidity. It shall be free from any substance foreign to milk. It may contain food additives. It shall conform to the microbiological requirement as laid down by FSSA. The said product shall also conform to the following requirements
The process of making dried milk involves eliminating water from milk, primarily through spray or roller drying. It is regarded as a significant sector of the dairy industry and is made from whole cow, buffalo, or standardized milk. Skim milk powder (SMP) is made from milk after the fat has been removed whereas whole milk powder (WMP) is made from whole cow or buffalo milk FSSA (2006) Standard Of Milk Powder According to FSSA (2006), Milk powder is the product obtained by partial removal of water from the milk of cows and/or buffalo. The fat and/or protein content of the milk may be adjusted by the addition and/or withdrawal of milk constituents in such a way as not to alter the whey protein to casein ratio of the milk. It shall be of uniform color and shall have pleasant taste and flavor, free from off-flavor and rancidity. It shall also be free from vegetable oil/fat, mineral oil, thickening agents, added flavor, and sweetening agents. It may contain food additives. It shall conform to the microbiological requirements prescribed by FSSA (2006). Water activity, high storage temperatures, longer than usual storage times, high product moisture content, high processing temperatures, and container headspace are some of the variables that affect the Maillard reaction in dried milk. Casein and whey proteins are the major proteins present in milk. Unlike casein, whey proteins are heat-labile. Whey protein fractions present in milk are α-lactalbumin, β-lactoglobulin, bovine serum albumin, immunoglobulin, euglobulin, and lactoferrin. β-lactoglobulin and κ-casein interact during heat treatment. When milk is refrigerated for longer than 24 h, it forms γ-casein and protease-peptone fractions.
One of the most consumed and well- known milk products in the Indian subcontinent is ghee. It is a by- product of tradition, prepared both at organized dairy plants and the household level for a well- established market. Ghee is traditionally made from the milk of cows or buffalo. The tetrapyrrole pigments biliverdin and bilirubin are responsible for the distinctive color of buffalo ghee. On the other hand, ghee is golden yellow due to the presence of carotenoids in cow’s milk. Ghee’s composition changes according to the kind and feeding habits of the animal and can differ from place to place and season to season. In addition to, being a substantial source of fat- soluble vitamins, essential fatty acids, and other growth- promoting components, ghee is a rich source of energy. Its value as food for humans is enormous. Additional attributes related to medicine are present in ghee. Ghee can improve one’s physical and mental attributes and treat eye conditions like ulcers. Ghee is used in religious and ceremonial rites in addition to being consumed. Composition Ghee is a complex lipid composed of mixed glyceride which makes up 99–99.5% of its total content. In addition, it has trace amounts of calcium, magnesium, phosphorus, iron, copper, and fat- soluble vitamins, tocopherols, carbonyls, hydrocarbons, carotenoids, free fatty acids, phospholipid, sterols, and sterol esters
Being an essential component of the rich Indian past, traditional dairy products and a sophisticated classification of confections have played a significant role in the Indian economy. Depending on how it is processed, it has significant social, cultural, and economic significance. These products have been developed over a long period using a combination of experience, traditional wisdom, and culinary skills. India is emerging as the highest milk- producing country in the world with an annual production of 221.1 million tons in the year 2021–22 (Source: Basic Animal Husbandry Statistics, MoFAHD, DAHD, GoI). An estimated 50% of the milk produced in India is used to make a range of traditional dairy products, including paneer, dahi, ghee, khoa, and shrikhand. The product is not only well- established in the Indian market, but it also has significant export potential due to the large Indian diaspora living all over the world. All native milk products that have developed over time using locally accessible technologies are referred to as traditional Indian dairy products or Indian indigenous milk products. The Indian masses’ economic, social, religious, and nutritional well- being are greatly influenced by traditional dairy products. Classification of Traditional Indian Dairy Products Traditional dairy products in India are typically made, packaged, and/or sold using time- honored methods without the use of machinery or meticulous documentation of the procedure. These products do, however, have several technological advantages, including their widespread appeal, reduced cost of production, straightforward manufacturing process, adoption at the rural level or collection center, large profit margin, and abundance of employment opportunities. These products are categorized according to the manufacturing principle.
The terms “cultured dairy foods,” “cultured dairy products,” and “cultured milk products” are other terms for fermented dairy products. Lactobacillus, Lactococcus, Leuconostoc, and other lactic acid bacteria, along with yeasts in certain products, are used to ferment milk to make these dairy products. The product’s shelf life is extended through fermentation, which also improves the product’s taste and milk’s digestibility. There is a wide variety of fermented milk products available, each with unique flavors and attributes. The following categories apply to fermented milk products, based on the type of fermentation. Changes in Nutrients Resulting from Fermentation Fermentation lowers the lactose content in fermented milk products; however, if the starting milk is concentrated or fortified, the finished product’s lactose content may be higher than that of liquid milk. The composition and content of protein and total amino acids are comparable to those of raw milk. Casein degradation is small compared to cheese, accounting for not more than 1% of the total protein. While some products of casein degradation are used by the starter microorganisms, others build up as free amino acids in the fermented kinds of milk. The amounts of free amino acids that build up differ depending on the species. Generally, proline is increased in large quantities, followed by serine, alanine, valine, leucine, and histidine. As a result of continuous starter culture activity, the level of free amino acids increases during storage. A limited degree of lipolysis occurs during the manufacture of fermented milk. The amount varies depending on the type of species, but the pattern and concentration of free fatty acids are both impacted. During fermentation and the breakdown of amino acids, trace amounts of volatile fatty acids are also produced.
Food adulteration is a global issue, and because there are insufficient regulations and oversight, developing nations are more vulnerable to it. But in many nations, food adulteration has gone unnoticed. Contrary to popular assumption, milk adulterants can, regrettably, present major health risks that result in fatal diseases. Modern milk adulteration involves increasingly complex techniques, necessitating state- of- the- art research to identify the adulterants. Because milk contains so many nutrients that are needed by both adults and infants, it is referred to as the ideal food. In terms of protein, fat, carbohydrates, vitamins, and minerals, it is among the best sources. Regretfully, milk adulteration is a very common problem worldwide. Potential causes could be the gap between supply and demand, the perishable nature of milk, the low purchasing power of the consumer, and the absence of appropriate detection tests. Because there is insufficient oversight and inadequate law enforcement, the situation is substantially worse in developing and underdeveloped nations. While quantitative detections of adulterants in milk are varied and complex, qualitative detections can be carried out simply using chemical reactions. The type of quantitative detection methods used depends on the milk’s adulterants. Typical Adulterants in Milk The addition of vegetable protein, milk from different species, whey addition, and watering are the main adulterants in milk that are known to be economically motivated. There is no serious health risk associated with these adulterations. Some adulterants, though, are too dangerous to ignore. Urea, formalin, detergents, ammonium sulfate, boric acid, caustic soda, benzoic acid, salicylic acid, hydrogen peroxide, sugars, and melamine are a few of the main adulterants in milk that have been shown to have serious negative health effects.
Electrophoresis The mobility of ions in an electric field is the basis for the separation method known as electrophoresis. Ions that are negatively charged move toward a positive electrode, while those that are positively charged move toward a negative electrode. Usually, one electrode is biased either positively or negatively, and the other is at the ground for safety reasons. Ions can be distinguished from one another based on their size, shape, and overall charge, which determine their migration rates. Poly Acrylamide Gel Electrophoresis (PAGE) Introduction Electrophoresis is an electrochemical process in which substances with a net electric charge migrate under the influence of an electric current. This migration occurs in an agar gel or a liquid- filled buffered matrix such as cellulose acetate. Positively charged substances travel toward the cathode (negative electrode), while negatively charged substances go toward the anode (positive electrode). Different substances move at different rates depending on their charge. This movement is called electrophoretic mobility. Proteins are charged molecules. They have a positive as well as a negative charge. Among proteins, particularly caseins, they have different contents. The charge density also varies depending on the molecular weight. Proteins have a net negative charge at a pH above 4.6, and hence they move towards the anode (positive electrode) when subjected to an electric field under alkaline conditions. Due to differences in the charge of individual protein fractions, their migration rates also differ and are hence separated into distinct bands. These bands are stained with the dye amido- black, destained with 7% acetic acid, and observed for the electrophoretic pattern.
The primary constituents of milk are water, fat, protein, sugar (lactose), minerals, vitamins, and enzymes. Milk is a thin emulsion made up of two phases: A continuous aqueous colloidal phase and a dispersed phase of oil or fat. It is an opaque white liquid containing fat in an emulsion, protein, and a few minerals in a colloidal suspension, and lactose along with soluble proteins and a few minerals in a true solution. The physical characteristics of milk are comparable to those of water, but they are altered by the degree of dispersion of the colloidal and emulsified components as well as the presence of different solutes, such as salts, lactose, and protein, in the continuous phase. Physical Appearance, Color and Optical Properties Fat globules and casein micelles scatter light, giving the appearance of turbid and opaque milk. The way that molecules scatter light has an impact on optical characteristics. When the wavelength of light and the particle’s magnitude coincide, light scattering happens. Consequently, light with shorter wavelengths is scattered by smaller particles and vice versa. Because casein micelles scatter blue light more than red light at shorter wavelengths, skim milk appears slightly blue. Cow’s milk has a creamy color because of beta- carotene, a carotenoid precursor to vitamin A. The greenish tinge in whey is due to the presence of riboflavin. Turbid and opaque due to scattering of light mainly by protein micelles and fat globules.
Vitamins are naturally occurring, vital nutrients that are needed in small amounts. They are important for bone and tissue health, wound healing, growth and development, immune system function, and other biological processes. These vital organic substances serve a variety of biochemical purposes. Vitamins, like minerals, are not biosynthesized by the body. Consequently, in order to maintain our health, we must obtain them from the food we eat or, in rare circumstances, supplements. Vitamins in Milk Together with water- soluble vitamins like vitamin C and B complex and provitamins, milk also contains a variety of fat- soluble vitamins like A, D, E, and K. Some of these vitamins do, however, have very low concentrations. Vitamin A (Retinol) Plant foods contain carotenoids, which are the precursors of vitamin A, whereas animal foods provide preformed vitamin A in the form of retinyl esters.
A Acetyl number 123, 124 Acid number 124 Acid phosphatase 15, 71, 72, 77, 78 Acidity 3, 10, 11, 67, 68, 84, 88, 92, 114, 116, 129, 131, 133, 134, 135, 136, 137, 138, 141, 221, 222, 224, 225 Adsorption chromatography 29, 165, 166, 172, 184 Affinity chromatography 177, 178, 183, 184, 193 Age Thickening 109, 110 Age Thickening 109, 110 Amino acid composition 27, 28, 29, 31, 107 Ascorbic acid 9, 133, 220, 221, 228, 239, 240
