Principles of Dairy Science and its Products PDF

Introduction Why does milk have a science called Dairy science? Milk is that wonderful food that God endowed with advantages and characteristics unlike any other food. Milk is considered the best food on earth and one of the rivers of paradise. Milk is a complete food for infant...

Introduction Why does milk have a science called Dairy science? Milk is that wonderful food that God endowed with advantages and characteristics unlike any other food. Milk is considered the best food on earth and one of the rivers of paradise. Milk is a complete food for infants and a semi-complete food for other ages. 1  Milk or Dairy !!!!! What is the source of "dairy"? Or when was the word dairy invented? Origin 1250–1300 (Middle English daierie and other forms), from dey (“dairymaid”) + -ery. Therefore, the word “Dairy” is more comprehensive in meaning than the word “milk”. The Basics of Liquid Milk First: Definition of milk: It is the natural secretion of the mammary glands of mammals that is obtained from the complete, regular, clean milking of one or several animals, from one or several milkings, without any of its components removed or added to it. Milk is suitable for human nutrition. The most important of which are cows and buffalo, goats, sheep, camels, horses, and human milk. All mammals are characterized by secreting the milk for feed their young. The milk of all mammals is similar in the composition of the substances contained in it, but they differ only in the proportions of these components. Second: biosynthesis and secretion of milk: Drops of milk are created in special glands called mammary glands. The udder is an oily skin formation. The number of mammary glands in mammals varies according to their 2  species, as their number is proportional to the number of births that each species gives birth to in one period. In humans, sheep, goats, and horses, there are only two, while in cows and buffalo, there are four. As for the dog, there are eight to twelve. Inside the udder of animals, there are milk production units called alveolus, which in turn consist of a single layer of epithelial secretory cells wrapped around it forms a storage area called the lumen, which is connected to a system of channels. The epithelial cells of the vesicles are surrounded by another layer of other cells called Myoepithelial cells and Surrounded by blood capillaries (see illustration). The raw materials that make up milk are transported through blood carriers to the secreting epithelial cells, and it takes 400–800 liters of blood to produce one liter of milk. https://www.youtube.com/watch?v=Zvjw9OLHf24 3 The most important substances that are created or formed inside these epithelial cells are: Proteins: They consist of amino acids in the blood. After that, casein begins to assemble in the Golgi vesicles inside the epithelial cells. Lipids: Fatty acids containing 4–14 carbon atoms are created inside epithelial cells, while fatty acids containing 16 carbon atoms and higher are formed as a result of the hydrogenation process inside the stomach of ruminant animals and are transported directly into the blood. Lactose: The osmotic pressure of milk is balanced with the blood and is controlled by lactose, potassium, sodium, and chlorine, as lactose synthesis regulates the amount of milk excreted. 4  Third: The nutritional value of milk: Milk contains many compounds such as fat, protein, sugar, mineral, and vitamins in proportions appropriate to the body’s needs, so milk is called a complete food. In addition, its digestibility rate is very high compared to other foods. While the digestible percentage of milk is (98–99%), the digestible percentage of other animal foods is (95–97%), while grains and bread are digested (85–90%). As for vegetables and fruits, they are digested (83–90%). The components of milk are characterized by special characteristics, which we summarize as follows: 1-Fat: Milk fat contains essential fatty acids that are necessary for the human body, such as linoleic and arachidonic, which the human body cannot produce. Milk fat is characterized by special natural characteristics, such as its melting point suitable for the human body. It also contains other 5  compounds such as phospholipids, sterols, and carotenoids, and these substances have a vital role. 2- Proteins: Milk proteins are considered to have a high biological value and are even considered a protective food through their amphoteric properties (neutralizing excess acidity and alkalinity). Mother’s milk contains 1.8% protein, which is small, while cows contain 3.7%, while dog milk contains 7.3%. The higher the percentage of protein in the milk, the faster the infant grows. So a human infant doubles its weight within 180 days, a calf doubles its weight within 47 days, and a dog doubles its weight within only 9 days. 3- Milk sugar (lactose): Lactose is considered a source of energy, as each gram of sugar (as well as protein) generates 4 calories. Lactose is characterized by its low sweetness and low solubility, which helps not to strain the senses of taste and not get bored from eating it frequently. It is also characterized by its weak absorption in the digestive system, so most of it passes into the large intestine creates more suitable conditions for acidic fermentations that reduce putrefactive fermentations. This sugar also helps increase the assimilation of calcium, phosphorus, and magnesium and preserve them in the tissues. 6 4-Minerals: Milk is considered an excellent source of calcium, as it is relied upon to compensate for the deficiency in other foods that are poor in calcium, such as grains. Chlorine is involved in the formation of hydrochloric acid, which is an essential part of the digestive gastric juice, and sulfur is involved in the formation of skin, hair, and nail cells. Some mineral ions, such as potassium and calcium, play an important role in regulating the heartbeat and nerve sensitivity. 5- Vitamins: These are substances that the body needs in small quantities for normal metabolism, and they protect the body from many diseases of malnutrition. Milk is characterized by containing most of the known vitamins and is considered an important source of vitamins A, B2, B1, and a good source of vitamin E, given the insufficient amount of vitamins C and D. Fourth: milk production: At birth, the udder begins to secrete milky fluid called colostrum. It is known for its salty and yellowish color. It contains large amounts of whey proteins and a fair amount of antibodies to help protect the infant until its immune system acquires natural protection. Within 72 hours of birth, 7  the colostrum begins to transform into the natural composition of milk, which is used as a source of nutrition. During the period of milk production, which lasts on average for 305 days, the amount of milk produced is about 7000 kilograms (for high-yielding foreign livestock). This quantity of milk is considered more than the needs of the infant animal, as it needs 1000 kilograms for growth. The highest rate of milk production reaches during the 2–3 months after calving, giving 40–50 liters/day. It is noted that the cow reaches the highest rate of milk production in the third milking season, and it can maintain this rate until the fifth or sixth milking season. Fifth: The milking process: The milking process is stimulated either by calves suctioning the teats during feeding, washing the udder with a warm cloth, or manual massage (cuddling), as such processes lead to the release of a hormone called oxytocin from the pituitary gland located below the brain to begin the process of producing milk. As a result of this stimulation process, the muscles begin to put pressure on the alveoli so that the milk flows from them to the udder quarters storehouse and from there to the udder storehouse. This is called a “Reflexive drop". The milk is forced to descend to the teat storehouse and then to its canal during the milking process due to the suction of the milk machine. The 8  effect of the Reflexive drop is reduced as the level of oxytocin decline within 4–7 minutes; after that, it becomes difficult to continue the milking process. Types of milking: Manual milking Automated milking (machine milking) Sixth: Milk of various animals: Each type of milk contains the same components but in varying proportions. For example, horse milk is considered the highest milk in the percentage of water (90.5%), the percentage of fat in buffalo milk is twice that of cow’s milk, and human milk is considered the highest in the percentage of lactose (6.8%). The next table shows that rabbit milk contains a high percentage of protein, fat, and minerals, and this is proportional to the speed of the newborn’s growth, as the rabbit’s weight doubles after six days. While this period increases to 180 days for a human newborn, and thus the percentage of protein and fat decreases to suit this slow growth of the newborn. For a cow newborn, it takes 47 days and 15 days for sheep to double their weight. 9 * Factors affecting the composition of milk: 1- Type and breed of animal : The composition of the milk, as well as the amount of secretion, varies depending on the type of animal, and it is always noted that the animal with high secretion has a low percentage of fat in its milk. 2- The lactation season: Dairy cattle begin to milk on the day immediately following birth, and the composition of the milk in the first three days (clostrum milk) is very different from that during the lactation season. At the end of the lactation season, the percentage of some compounds, such as sodium chloride and non-fat solids, increases. 10  3- Age of the animal: Milk production increases as the animal ages (the lactation season) until the fourth or fifth lactation season is reached, then production decreases until the tenth lactation season, and the percentage of fat decreases as the animal ages. 4- Season of the year: The temperature and humidity in the air vary depending on the season of the year, and it has been found that the percentage of fat and protein in milk increases with a decrease in air temperature, and the amount of milk decreases in extreme heat or extreme cold. 5- Animal health: Mastitis disease causes a noticeable change in the composition of milk, as the milk is close in composition to blood serum, so the percentage of chlorides and whey proteins increases and the percentage of lactose, casein, and fat decreases. 6- Nutrition system (feeding): Starving the animal leads to a decrease in milk production and a decrease in non-fat solids. Feeding green forage also leads to an increase in the amount of carotene in cow’s milk and an increase in the percentage of unsaturated fatty acids. As for increasing the percentage of protein in the diet, it does not lead to an increase in milk, while it may increase the percentage of non-protein nitrogen. 11  7- The effect of the milking process: Increasing the length of the period between milkings leads to an increase in the amount of milk and a decrease in the percentage of fat. The process of complete milking and completely filtering the milk from the teats (distillation) leads to an increase in the amount of milk as well as the percentage of fat. * Mammalian milk can generally be divided into: 1- Milk that forms a hard coagulated when cured with acid or rennet. This includes the milk of sheep, buffalo, goats, and cows. 2- Milk forms a very soft curd when coagulated with acid or rennet. This includes human and mare milk due to its low content of casein and its high content of albumin, globulin, and non- protein nitrogenous substances. If we compare the types of milk with each other, taking cow’s milk as a basis for comparison, we find that by comparing it with mother milk, while both contain similar percentages of solids. As for the type of reaction, we find that cow's milk is amphoteric (neutral), while mother's milk is alkaline. As for buffalo milk, it differs from cow’s milk in its white color and the increase in solids, especially fat and protein. 12  As for goat milk, it is very similar in its chemical composition to cow’s milk. The most important differences are a slight increase in the percentage of mineral salts and a decrease in the percentage of protein and sugar in goat milk. Cow milk is also distinguished by containing the carotene. Sheep milk is also similar to buffalo milk, but the difference between them is in the higher percentage of protein and ash in sheep milk than buffalo milk. As for the milk of the donkey and the mare’s milk, they are much closer in their characteristics to mother’s milk than to cow’s milk. Mother's milk has a higher percentage of sugar and a lower percentage of protein and minerals than cow’s milk. * Factors that affect the percentage of fat in milk: 1- Type of breed of livestock: The milk of Jersey cows contains a higher percentage of fat than the milk of Friesian cows. 2- Individual livestock: This is due to genetic factors. 3- Age of cattle: The percentage of fat increases gradually until the fourth or fifth birth and then gradually decreases in subsequent births. The decrease in the percentage of fat in milk is the basic change that occurs in its composition as a result of the ageing of cattle. 13  4- Milking season stage: The percentage of fat in milk decreases during the first two or three months after the start of milking and then increases gradually until the end of the milk season, especially in the last weeks. 5- Season of the Year: The percentage of fat in milk varies depending on the season of the year, and this is due to the effects of temperature and humidity. The percentage of fat in milk increases by about 0.2% whenever the temperature decreases by 10°F in the range between 72 and 77°F. 6- Feeding The quantity or type of feed has no effect on the minimum percentage of fat in milk as long as the animal gets the feed that meets its needs. However, if the livestock does not get enough feed, the amount of milk produced decreases while the percentage of fat increases. It has been found that the abundance of feed is poor. Fiber may result in lower milk fat. 7- The period between the milking: The longer the period between milkings, led to increase the amount of milk and the lower percentage of fat in the milk, and vice versa. 8- Stages of the milking process: The first parts of the milk contain a lower percentage of fat than the end of milking. Therefore, care must be taken to 14  completely empty the udder of milk, as it is rich in fat. This process is known as distillation or scattering. 9- Condition of livestock during birth: If the cattle are in good condition and not emaciated or sick during birth, the percentage of milk fat will be high. 10- Livestock discomfort and drug: Changing milkers or fear of annoying noises often causes cattle to hold on to part of their milk, causing the amount of milk produced to decrease. Some drug that may be given to cattle also affect the percentage of fat in milk. If drugs cause cattle to abstain from eating, the resulting lack of milk is accompanied by an increase in the percentage of fat. * Factors that affect the percentage of non-fat solids in milk: Every increase in the percentage of fat by 1% is accompanied by an increase in the percentage of non-fat solids by 0.4%, as the percentage of non-fat solids is affected by the same factors that it affects the percentage of fat in the milk. Seventh: Abnormal milk: A - Colostrum: It is the milk produced by livestock after giving birth, and it differs significantly from natural milk. The animal continues to secrete it until it returns to secreting normal milk about 4–7 days after birth. Colostrum is characterized by a strong odor and a slightly bitter taste, and there is no harm in consuming it except that it causes some trouble. 15 * Colostrum milk differs from natural milk in the following: 1- Colostrum milk contains a high percentage of proteins, especially albumin and globulin, so it becomes curdled when heated. 2- The high percentage of iron in colostrum milk is about 17 times that of natural milk. 3- Reducing the percentage of lactose in colostrum milk. 4- The percentage of mineral salts in colostrum milk is high, so its taste is slightly salty. 5- Colostrum milk is more viscous in consistency, so it may clog the separators when it is skimmed. 6- The color of coarse milk is yellowish, as its fat contains 8 times the percentage of carotene in cow’s milk, and it also contains 6 times vitamin A and twice vitamin D. B - Mastitis: It is a medical condition that results from the entry of some types of microbes into the mammary glands through a wound in the udder, which results in inflammation in those glands, which leads to the secretion of milk containing a large number of microbes that cause inflammation, white and red blood cells, and epithelial tissue cells. The disease is characterized by the presence of congestion and redness in the mammary glands. The udder may be accompanied by an increase in the animal's temperature, psychological tension in the animal's case, and pain when touching the udder or the animal. As the condition progresses, fibrosis and ossification of the tissue occur, a change in the shape of the udder occurs, and the endocrine glands may lose their ability to secrete milk. * Changes that occur in milk produced from cattle infected with mastitis: 1 - Decrease in the amount of milk produced. 16 2- A change in the apparent and sensory characteristics of the milk, as it is bloody and purulent, has a pungent odor, and may be bluish and watery. 3- The total number of bacteria in milk exceeds 10,000 microbes per milliliter. 4- Increase in white and red blood cells and epithelial tissue cells. 5- The milk reaction changes from acidic to alkaline (the pH increases from 6.6 to 7.4). 6- The chemical composition of the milk changes as non-fat solids, casein, lactose, citric acid, and phosphorus, calcium, potassium, and magnesium salts decrease, while the percentage of albumin, globulin, fat, sodium salts, chlorine, and sulfur increases. It is noted that this increase in some compounds and their decrease in others work to stabilize the osmotic pressure of the milk. * Harmful effects of using milk produced from cattle infected with mastitis: 1- From a health perspective: The presence of hemolytic streptococci microbes leads to an infectious sore throat or scarlet fever. The presence of staphylococcal microbes that cause food poisoning produces toxins that cause food poisoning in humans, despite boiling the milk before drinking it. 2- From a manufacturing standpoint: - The weak ability of milk to withstand heat, as it is prone to curdiness when boiled, and thus it is not suitable for making dairy products that are heated to high temperatures, such as sterilized or concentrated milk. - Difficulty in using starter culture in the manufacture of yoghurt or cheese, because some types of microbes that cause mastitis secrete biological substances that counter the activity of the starter culture’s lactic acid 17 bacteria. - Increasing the softness of the resulting curd by adding rennet. - Spoilage of the cheese resulting during processing as a result of the increase in the number of unwanted bacteria in the milk, many of which affect the protein in a way that creates an unacceptable taste and unpleasant odors in the cheese. 18  Part Two: Dairy chemistry and physics First: The natural state of the basic milk compounds: From a natural perspective, milk is a complex liquid that contains many components that exist in many natural forms or states, including the emulsion, the colloidal, and the true solution. * Fat: Fat is found in natural milk in the form of tiny globules whose diameter ranges between 0.1 and 15 micrometers (micrometer = micron = 10-3 millimeters), surrounded by a membrane that makes it spread in the milk in the form of an emulsion. The density of fat at 20°C is 0.915 g/cm3 and is the index of refraction at 15°C is 1.459– 1.462, the melting point is between 28 and 33°C, and the degree of solidification is between 19 and 24°C. * Proteins: 1- Casein protein: It exists in the form of fine grains with a diameter ranging between 10-300 nanometers (nanometer = 10-6 millimeters). It is distributed in milk in a colloidal form, and its average density is 1.11 g/cm3. 2- Whey proteins: It exists as a single molecular form or aggregated in a few, forming very fine grains with a diameter of 3-6 nanometers, and its average density is 1.34 g/cm3. * Lactose sugar: It exists in a dissolved state, and it is a real solution that can be separated into a crystalline form when the whey is concentrated. Its average density is between 1,540 and 1,589 g/cm3, depending on its natural form, and its degree of sweetness is 25% of the sugar lactose. 19  *Minerals: Some of them exist in a dissolved form, such as sodium and potassium, and some are distributed between the dissolved and colloidal forms, such as calcium, phosphorus, and citrate. Second: Chemical composition of milk: Mammalian milks contain the same ingredients; the only difference is in the proportions of these ingredients to suit the newborn’s needs for growth and movement. Milk contains more than a thousand chemical compounds, each of which has its own nutritional importance and impact on the characteristics and properties of various milk products. * Milk compounds are divided according to their percentage in milk into: 1- Major components: They include water, fat, proteins, sugar, and mineral. 2- Minor components: These include vitamins, enzymes, flavour compounds, and others. 20  * We will explain in detail the most important properties of milk components and their relationship to the dairy industry: 1. Water: Water is the largest part of milk, and its percentage is about 87% in cow’s milk and 83% in buffalo’s milk. Most of the water is in its free form, and a small percentage of it (3-5%) is bound to casein, whey proteins, and the surfaces of fat granules. Water has technological importance. In various chemical reactions and fermentations in milk and its products. 2. Milk fat: * Chemical properties of milk fat: Fat is found in milk as an emulsion, dispersed in milk serum in the form of fine spheres surrounded by a thin coating that has properties different from milk fat and plasma. The milk fat is in an emulsified state, which prevents it from gathering and forming an oily layer on the surface. This membrane is composed of a group of proteins, enzymes, and phospholipids. The membrane of the fat granule may be exposed to many cases of change and damage, partially or completely, as a result of heating, cooling, or shaking. * Components of the fatty substance: Milk fat consists of a mixture of triglycerides, among which fatty acids are distributed through hundreds of random exchangeable structures, as well as substances associated with the fat (phospholipids, sterols, carotenoids, and vitamins) in addition to the coating layer (proteins, phospholipids, and enzymes). When one wants to determine the physical properties of fats, it has been observed that small amounts of mono- and diglycerides and fatty acids are present in free form in freshly milked milk, which could be the result of premature fat decomposition or incomplete synthesis. 21  * Triglycerides: Triglycerides are created within milk-secreting cells and represent 98.3% of milk fat. These triglycerides are composed of the combination of a glycerin molecule with three different fatty acids. Fatty acids constitute about 85.5% of the weight of milk fat, while glycerol is 12.5%. Deterioration of milk fat Hydrolytic rancidity: It occurs as a result of the hydrolysis of milk fat by the enzyme lipase and the release of short-chain fatty acids, especially butyric acid. The 22  source of the enzyme is either the milk itself or some of the microbes that reach it. The pasteurization process leads to the elimination of the enzyme and stops its activity, and the lack of moisture hinders the occurrence of hydrolysis. Oxidative rancidity: This type of rancidity occurs as a result of the oxidation of fatty acids by the action of oxygen, aided by exposure of milk to direct sunlight A- Ketonic Rancidity It arises as a result of the oxidation of some low-molecular-weight saturated fatty acids and forms volatile compounds such as methyl ketones, which give the product a taste similar to the rancid taste of coconut. B- Oxidative rancidity: It arises as a result of the oxidation of unsaturated fatty acids by oxygen, especially linoleic acid, and the formation of peroxides. Its rapid appearance is aided by exposure of milk to direct sunlight, contamination of milk and its products, especially fatty ones, with metals such as copper, or the presence of traces of old, previous fat in the ghee storage container. 3. Milk proteins: Milk contains a group of nitrogenous compounds, most of which consist of proteins and a small portion of non-protein substances. 23 24 25  * Milk proteins are divided into: A - Proteins that coagulate with rennet or precipitate by direct acidification of milk at pH 4.6, and these include casein. B - Proteins that do not coagulate with rennet and do not precipitate by acidification at pH 4.6. These include whey proteins, which are divided into: - Proteins that precipitate by heating at 85°C: They include albumin and globulin. - Proteins that do not precipitate by heat: they include protease peptone. * Caseins: Casein represents about 80% of milk proteins. Casein consists mainly of alpha (αs1), alpha (αs2), beta (β) and 26  kappa (κ). The distinctive feature of all casein fractions is that they are proteins often linked to phosphate groups in an esterified form with the amino acid. Both alpha (αs1) and alpha (αs2) are considered to be well sensitive to calcium. Likewise, beta (β) can be precipitated, but it is less sensitive than them. As for kappa-casein, it is considered the most resistant casein radical to calcium. kappa casein consists of a hydrophobic part called "para kappa casein" and a hydrophilic part called "glycomacropeptide" (GMP), or more precisely, "casinomacropeptide" (CMP), and kappa casein is split by the Renin enzyme when the bond between phenylalanine (105) and methionine (106). * Enzymatic coagulation: This is done through two stages: the first is enzymatic, and the second is non-enzymatic, as shown in the following illustration: 27  - Enzymatic stage: In this stage, the rennin enzyme (extracted from the fourth stomach of suckling calves) is adsorbed onto the surfaces of casein molecules and then begins to attack kappa-casein (the protective coating that protects the casein radicals from being affected by calcium ions) at the bond between phenylalanine (105) and methionine (106). In the peptide chain of kappa casein, it is hydrolyzed, and two parts are formed: Para- casein and Glycomacropeptide. - Non-enzymatic phase: In this stage, casein micelles accumulate due to calcium ions in the form of a three-dimensional network, forming the curd, between which the remaining components of the milk are trapped. The intensity of the cohesion of the curd depends on the available calcium ions in the medium. The temperature and time of coagulating are considered important factors for 28  both stages of coagulating, as they increase the reaction rate at 40°C. * Acidic coagulation: Casein is found in milk in the form of a hydrogen-calcium caseinate complex bound to tricalcium phosphate and surrounded by a halo of negative charges. If acid is present, whether from the fermentation of lactose as a result of microbial activity: Or if the acid is added intentionally, the following happens: -The acid combines with the calcium bound to the casein and also with tricalcium phosphate to form a soluble calcium lactate salt and a soluble calcium hydrogen phosphate. -The release of hydrogen ions and their neutralization of negative charges lead to a decrease in the pH to 4.6, which corresponds to a percentage of acidity (0.50-0.65%) as lactic acid. This is known as the isoelectric point of casein (at which the number of positive charges equals the number of negative charges). 29  -Adding excessive amounts of acid leads to a decrease in the pH to less than 4.6, and then the casein begins to acquire positive charges, and upon reaching pH 2.5, the casein begins to spread again. * Uses of casein: 1. As food, as it is added to fortify some foods or feed 2. Covering and weighing the leaves 3. Manufacture of plastics, buttons, glasses hangers, and electrical insulators 4. Manufacture of synthetic fibers used in the textile industry 5. Manufacture of some adhesives * Whey proteins: The most important components of whey proteins are β- lactoglobulin, α-lactalbumin, blood serum proteins (BSA), and immunoglobulin. 30  4. Lactose: Lactose (milk sugar) is a disaccharide made up of two different types of monosaccharides (glucose and galactose). 5. Milk minerals (ash): Milk contains all the mineral elements necessary for human nutrition. 31  6) Vitamins: Vitamins are organic substances essential for many life processes. Milk contains fat-soluble vitamins such as A, D, E, and K. Vitamin A is derived from beta-carotene. Milk is also an important food source of water-soluble vitamins: B1: Thiamine B2: Riboflavin B3: Niacin B5: Pantothenic acid B6: Pyridoxine B12: Cyanocobalamin. In addition of vitamin C 32  7. Milk Enzymes: Lipoprotein lipase Plasmin Phosphatase Peroxidase Catalase Lactase Lipase Protease 8- Dyes and gases: Pigments in milk include those that are soluble in fat, such as carotene and xanthophyll, which are reddish-yellow in color and cause the milk to be yellow, and those that are soluble in water, such as riboflavin, which color the whey a greenish color. Third: Physical properties of milk: 1) Density and specific gravity: Density is the weight of a given volume of a substance at a temperature of 20°C. Specific gravity is the weight of a certain volume of a substance relative to the weight of the same volume of water at a temperature of 20°C. 33  2) Boiling and freezing point: The boiling point of milk is105.5°C as the presence of lactose sugar and minerals. The freezing point of milk is ranges between -0.512 and - 0.550°C. 3) Acidity: There are several types of acidity in milk: Natural acidity: It is caused by the components of fresh milk (0.16-0.18%), half of which is due to the effect of acidic salts such as sodium hydrogen carbonate (NaHCO3) and free organic acids such as citric acid, and the rest of the acidity is due to the effect of casein and whey proteins (albumin and globulin). Developed acidity: It is called lactic acidity, and it results from the fermentation of lactose sugar and its conversion into lactic acid. 34