eChapters

Background
Milk is known as a whole food for human consumption. It is the first food of the newly born human mammals. Milk contains almost all the nutrients required for the patients, the elderly, pregnant mother and new born baby. There is no doubt that milk plays a significant role in human development. We can prepare many physical forms of milk like cheese, yogurt, ghee, and milk powder. The calcium content is higher in buffalo than in cows. Buffaloes are the second largest source of milk and produce 15 % milk. Higher biological value proteins, fat, soluble vitamins, fatty acids, amino acids, water-soluble vitamins, and calcium are all present in milk. The main antioxidant components of milk and milk products are sulfur, phosphate, zinc, and amino acids like cysteine (necessary to produce collagen).
Milk somatic cells are normal cells found in milk in small amounts (epithelial cells), some of which are leukocytes (white blood cells). When mastitis is infected or injured, leukocyte production rises. Milk with a low SC level produces superior milk products that last longer. Better milk management, better cleanliness, and correct nutrition all contribute to a decrease in milk SC, which indicates poor milk production hygiene and a cause of mastitis. Milk somatic cells are made up of both immunological and milk-producing cells. In terms of defense, somatic cells are the second line. During the routine process of milking, these cells are secreted in milk. Somatic cell count is a good tool for evaluating farm cleanliness in bulk milk and is utilized worldwide as an indication of udder health in individual milk. The most prevalent condition affecting dairy buffalo production and their health and well-being is mastitis. The somatic cell count consists of immune cells (75%), such as neutrophils, macrophages, lymphocytes, erythrocytes, and epithelial cells (25%). Investigators have made different attempts to exploit milk somatic cells as a potential non-invasive sample to diagnose early pregnancy udder health in bovines.

Physical Properties of milk
Procedure: Collect different types of market milk samples and study the  properties of milk. Boil the milk and note down the properties given in table 1 and record the observations

Milk is the one food for which there seems to be no adequate substitute. It constitutes almost the entire diet for the young of all mammals. Each species produces milk that is especially adapted to the growth of its own young, but milk from one species may be used as food for others. Since animals were domesticated centuries ago, the milk from various species such as cow, buffalo, goat and camel, has been used in the diets of people throughout the world. Only cows milk is of commercial importance in the United States, although small amounts of goat’s milk are sold.

Whole cow’s milk is approximately 88 percent water, 5 percent carbohydrate, 3.5 percent protein and 3.3 percent fat. Its nutrient content varies from species to species, from breed to breed, seasonally and even from the beginning of the milking to the end of the process. In the United States it is cow’s milk that is used commonly as a beverage and in food preparation. Therefore the milk discussed throughout this chapter is cow’s milk.

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

Abstract

Vitamin D or “sunshine vitamin” is an essential fat soluble vitamin required for healthy bones. It is responsible for enhancing intestinal absorption of calcium and phosphate. Its deficiency leads to osteoporosis and osteomalacia in adults and rickets and other bone deformities in children. Vitamin D deficiency is being reported to be quite common these days due to modernization accompanied with changes in lifestyle and environmental pollution which limit sun exposure for several individuals. Inadequate sun exposure results in reduced vitamin D synthesis and ultimately poor vitamin D status necessitating compensation through dietary intake. Dietary vitamin D intake is very low in India because of low consumption of vitamin D rich foods, absence of fortification and little use of supplements. It is becoming a major public health problem, needing immediate attention. Fortification of milk and milk products is the safe and effective approach to deal with widespread vitamin D deficiency as milk is consumed and liked equally by all age groups. This paper highlights the importance, sources, recommended allowances and other relevant issues related to vitamin D fortification and its health effects.

Homogenization is now a widely used industrial process in dairy production, essential for stabilizing milk and other liquid dairy products. Its main purpose is to prevent fat from separating out of the milk, ensuring a smooth, consistent, and uniform product. Milk is a complex emulsion comprising water, fat, proteins, carbohydrates, minerals, and vitamins. Among these constituents, fat plays a critical role in determining the texture, flavor, and overall sensory quality of milk and dairy products. In its natural state, milk fat exists in the form of globules of varying sizes, surrounded by a thin membrane that stabilizes them in the aqueous phase. These fat globules typically range in size from 2 to 10 μm and have a lower density than the surrounding water-based phase of milk. This difference in density causes the fat globules to rise and form a cream layer when milk is left undisturbed, leading to an uneven texture and separation during storage.
Homogenization is a mechanical process applied to milk to modify fat globules by forcing the milk under high pressure through a tiny orifice. This reduces the average size of the fat globules while increasing their number and surface area. Practically, this greatly minimizes the tendency of fat globules to rise and form a cream layer. The enhanced stability of homogenized milk is due to three key factors: the reduction in the average diameter of fat globules, as described by Stokes’ Law, which slows their upward movement; the uniformity in size distribution, which ensures globules rise at similar speeds, preventing clustering; and the increased density of fat globules caused by the adsorption of a protein membrane, bringing their density closer to that of the surrounding liquid. Additionally, heat pasteurization complements homogenization by breaking down the cryo-globulin complex, which otherwise promotes clustering and cream formation.
The smaller and uniformly dispersed fat globules create a smoother, creamier texture and enhance the mouthfeel. This process also contributes to the visual appeal of milk, making it appear whiter and more uniform. Homogenization is, therefore, an essential step in modern dairy processing, ensuring the stability, quality, and consistency of milk and other dairy products, while addressing the challenges posed by the inherent properties of milk fat and its lower density.

Milk impaction in neonatal calves is a condition characterized by the improper digestion or accumulation of milk in the abomasum, leading to digestive disturbances, discomfort, and potential health complications for the calf. This condition is most commonly seen in newborn or very young calves; typically within the first few days to weeks of life, as their digestive systems are still developing and may be more susceptible to dysfunctions. Causes of milk impaction
Several factors can contribute to milk impaction in neonatal calves. Understanding these causes is essential for prevention and treatment. The primary causes are:
1. Overfeeding or undigested milk: One of the most common causes of milk impaction is overfeeding, where the calf is fed more milk than it can digest properly. Overfeeding can overwhelm the capacity of the
abomasum, leading to a backup of undigested milk. Undigested milk in the stomach can ferment, creating an acidic environment that may disrupt normal digestion and lead to impaction.
2. Inappropriate milk temperature: Milk fed to calves should be at the proper temperature, usually between 38-39°C (100-102°F). Milk that is too cold can cause a delay in the digestive process and lead to impaction, as it may not be digested as quickly as milk at the ideal temperature. Similarly, milk that is too hot can cause digestive stress or irritation.

The first use of milk in a solid chocolate product is commonly attributed to Daniel Peter in 1875. Milk chocolate is the most popular type of chocolate, and milk ingredients are critical in delivering the highly desired properties and taste profile to consumers. Milk ingredients also have a significant effect on chocolate processing.

Milk is one of the most complex raw materials used by the food industry. A typical bovine whole milk has a solids content of about 13.5%, comprising about 3.4% protein, 4.6% fat, 4.7% lactose and 0.7% minerals.

Milk proteins can be classified as either caseins or whey proteins - typically found in milk

Introduction

There are manypeople all over the world who have a certain level of sensitivity or intolerance towards milk and milk products. The reactions to milk which involve the immune systemare termed as milkallergy, whereas, difficulty in the digestion of the milk and milk products is known as milk intolerance. Milk intolerance occurs due to malabsorption of milk sugar (lactose) in intestine, a condition in which lactose is not digested into its monomers (galactose and glucose) due to lower activity or insufficiency of lactase enzyme. Inability to digest lactose, which is a disaccharide present only in milk, is specifically known as lactose intolerance. However, hypersensitivity involves the adverse immune reaction(allergic reaction) inthe body causeddue to the ingestion of milk proteins. Milk and milk products are major source of basic as well as essential nutrients and cannot be skipped from the diet of the individual. It is a rich source of calcium,which is essential for the growth and reformationof bones. The decline in calcium may lead to thin, fragile bones that break easily, a condition called osteomalacia or osteoporosis in women. Thus, it is a matter of concern for both children andadults whoare allergic or intolerant towards milk and milk products and not getting enough calcium and other nutrients in diet. This chapter would provide more insight about milk intolerance and milk allergy/hypersensitivity and how to deal with it.

India

Milk legislation and regulations are designed to prevent fraud and adulteration. But they now cover many factors that affect sanitation and public health. Milk generally is classified into grades according to the care with which it is produced.

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 primary objective of dairy plant hygiene is to ensure the consistent daily turn-out of safe and clean products which comply with pure-food and public health laws. A secondary and commercially important aim is to preserve the keeping quality of dairy products and so enhance consumer confidence in them. An integral part of a dairy is the quality control laboratory. Continuous testing is necessary for many purposes, including equipment hygiene. Bacteriological standards of dairy products can be maintained only if the raw product is of good bacteriological quality and is protected against contamination from the equipment with which it comes in contact during all stages of processing. 
Many factors may influence the maintenance of dairy equipment in a hygienic condition; the most important are the dairy buildings, the materials and construction of the equipment, personnel, water supply, cleaning procedures, and laboratory control. It is quite impossible to place these points in order of importance, efficient control of dairy plant hygiene being dependent on proper attention to all factors.

10.1 Introduction

Milk is a unique substance in that it is both consumed, as fluid milk with minimal processing and it is the raw material used to manufacture a wide variety of products. From the nutrition point of view, milk is an almost ideal food and considered to be perfect food. The human body needs more than thirty distinct materials in its food supply. No single food stuff supplies all of them but milk supplies nearly all. Since milk by its nature is perishable and an ideal product for bacterial growth, so it must be carefully handled, both during production and while processing. This chapter focuses on the technological (processing) aspects of the transformation of milk into its various consumer products, including beverages, fermented products, concentrated and dried products, butter and ice cream.

Milk production in India is a subsidiary activity of agriculture in contrast to the organized dairy sector in the western countries. Farmers and landless labour maintain one to five milch animals. As a result, small quantities of milk are produced in a scattered manner. Due to this reason, milk procurement models from western countries, such as bulk cooling and bulk transportation are not applicable under Indian conditions. Collection of small amounts of milk is scattered over long distances and, therefore, poses a formidable challenge in maintaining the quality attributes and keeping costs down.

3.1. Rural Milk Collection

A systematic approach to rural milk collection suitable for the tropical climate and techno-economic conditions prevailing in India has been developed, based on the indigenous experience gained over the past few decades. In the first phase, extensive surveys are undertaken in the milkshed areas, where the milk plant is to be established. The second phase involves ‘route planning’ taking into account, availability of quantities of milk, access to roads for plying vehicles and distance from the site of dairy plant. Then zones are identified, representing equal costs of collection and transportation. In the third phase, planning is done for locating the primary collection centres as well as chilling centres, where, milk can be cooled to 4ºC before transporting to the milk plant. Milk may be collected from individual producers either by the contractor or by forming village level cooperative societies.

The goat milk has several peculiarities, being a food of high digestibility and high nutritional value.Goats can hardly compete with cattle or buffalo in milk production ability. Goats produce approximately 2% of the world’s total annual milk supply. Neverthless, goat is an important source of animal protein for the landless and marginal farmers of tropical countreis, in areas where other classes of livestook cannot possibly survive and for several classes of people allergic to cow milk. Goats contribute about 4 % of the total milk produced in India. Goats and sheep producing milk for people start with the beginnings of domestication. For thousands of years they have provided sustainance for the people. During the last 150 years genetic selection and better feeding conditions led to several superior goat and sheep breeds in some countries in terms of milk and solids productivity, proving a great potential for evolution in both species, and responding to an increasing market demand and popularity. Some sheep breeds can produce more than 1000 kg milk in one lactation and several goat breeds more than 2000 kg milk, but in physiologically comparable terms of 4% fat-corrected milk both species can be equal. Goat milk production leaders have been capable of producing 10 kg milk per day of lactation.

Goat has been referred to as the Poor mans cow or wet nurse in Europe. Goat provides the cheapest source of milk to the poor both in rural and urban areas. The milk of goats is sweet, nourishing and medicinal. Goat milk is white in colour. Goat milk is whiter than whole cow milk. Butter and cheese made from goat milk are also white, but may be colored during processing. Exploitation of goats as a source of milk for human beings dates back from antiquity. Goat milk has been acknowledged as an ideal food for the aged, the sick and convalescent as well as for infants and growing children. Ever since Cleopatra filled her bathtub with goat milk , fresh goat’s milk has been revered for its superior moisturizing properties.

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.

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.

The livestock sector, particularly the dairy sector, plays a vital role in India’s economy and contributes significantly to the country’s milk production. The continuous growth and development of this sector have led to India becoming the world’s largest milk producer. It has seen significant growth, with a Compound Annual Growth Rate (CAGR) of 13.36% from 2014-15 to 2021-22. This sector’s contribution to the total Gross Value Added GVa in agriculture and allied sectors has risen from 24.38% in 2014-15 to 30.19% in 2021-22, accounting for 5.73% of the total GVA in 2021-22. The country’s livestock population, as per the 20th Livestock Census, includes approximately 303.76 million bovines (cattle, buffalo, mithun, and yak), 74.26 million sheep, 148.88 million goats, 9.06 million pigs, and about 851.81 million poultry. The dairy sector stands as the single largest agricultural commodity, contributing 5% to the national economy and directly employing more than 8 crore farmers.

12.1. Introduction

Milking is the crucial operation in a dairy farm, as milk is the main source of revenue of a dairy farm. Milking is a labour intensive operation. About 50-60 percent of the total time of farm operation is required for milking and allied activities. Milking is an art which requires skill, patience, efficiency and experience. It should be handled quietly, quickly, gently, cleanly and completely, by avoiding any type of pain, annoyance or inconvenience to the animals. Possession of high yielding animals or good managemental conditions will not generate profit if the milking operation is inefficient.

Letting the cow to release its milk so the dairy farmer can extract it for personal use or to sell is the procedure of milking. Consequently, it is not totally a natural process. The natural process must be manipulated by the dairy farmer to his advantage. Therefore, in order to control the natural process, one must first understand it. The process of producing milk from blood-derived basic materials by alveolar cells and storing it in the alveolar cavity is known as milk secretion. Only when the alveolar cavity is full and the pressure on the alveolar cells prevents further secretion does this continuous process come to an end.