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Milk; Definition, Composition and Nutrition (Detailed Explanation)

Milk is a porcelain-white liquid with a distinctive smell and taste secreted by female mammals to feed their newborns. It begins to be secreted after the calf is born and continues to be secreted in varying amounts and for a period depending on different parameters, especially species and breed.

To define milk for food experts, milk is a polydisperse food in which the fat phase is in emulsion, the proteins are in colloidal dispersion, and the lactose and minerals are in a saturated solution.

*The term “milk” refers to “cow’s milk”; by milk, we mean cow’s milk unless another animal species is specified.

The milk secreted within the first 1-2 days immediately after birth is called colostrum, which has a very different appearance, characteristic and nutritional value from milk. The first milking colostrum is the highest quality colostrum. As time progresses, the quality of the colostrum decreases; Finally, 24-48 hours after milking, regular milk begins to be expressed. (For more detailed information about colostrum, see Colostrum; Composition, Properties and Health Benefits)

When milk is mentioned, a food with a standard structure or composition should not come to mind. For example, human milk’s structure and composition differ from cows, sheep, or other mammals. Or the milk of one breed of cow has a different composition ratio than the milk of the other. Or a cow’s milk has different composition ratios and properties in different seasons. These examples can be multiplied.

The structure and composition of milk are highly variable, and as far as it is known today, more than ten factors affect the composition and amount of milk.

Composition of Milk

As far as is known today, milk contains about 500 different components. Major components such as water, carbohydrates, lipids (molecules such as fat and fat-like) and protein make up more than 99% of milk. Components such as minerals, vitamins, hormones, and gas are diverse and comprise the remaining 1%.

In some sources, components that makeup 99% are called “major components“, and components that make up 1% are called “minor components.”

On the other hand, some sources separate the components of milk as water and dry matter. Dry matter is evaluated separately as “fat-free dry matter” and “fat.” In general, the composition of milk is as follows;

Composition of milk

The composition of the milk is generally as in the graph. However, the amount and ratio of these components in milk can vary greatly depending on the mammalian species. In the table below, the compositions of milk of some species are given;

Milk composition of different species

*Ash term; refers to the amount of ash remaining after burning milk. Not all of the ash is “usable mineral for the body,” but it is used to express the amount of mineral since most are “usable minerals for the body.”

1. Water

Generally, the water content of milk varies between 65% and 88%, depending on the species. The water content of human milk is approximately 87.6%, cow’s milk 87.4% and sheep’s milk 81.2%.

2. Carbs (Lactose)

Milk contains only lactose as a carbohydrate. Another name for lactose is “milk sugar.” The term lactose comes from the Latin word “lac,” meaning milk and the French word “ose“, meaning carbohydrate building blocks. Lactose is a disaccharide formed by combining a galactose and a glucose molecule.

Different animals’ milk contains different amounts of lactose. For example, human milk contains an average of 7%, while cow’s milk contains an average of 4.7% lactose. This value is, on average, 1.8% in whale milk.

Considering the lactose ratio in dairy products, a small portion of the lactose contained in milk in yogurt is used by microorganisms. The addition of milk powder during production causes an increase in the lactose ratio of yogurt. However, it is known that lactose-intolerant individuals can digest the lactose in yogurt easier than in the same amount of milk.

Most cheeses are lactose-free, except some fresh and soft cheeses. This is because lactose is dissolved in the water phase of milk; during cheese making, the lactose in the milk is removed from the cheese mass along with the whey. Therefore, lactose-intolerant individuals can easily consume most cheese, except some fresh and soft cheeses (such as feta cheese and curd).

3. Protein

In fact, milk proteins are a very comprehensive and complex subject, and a 200-page book could easily be written on it. Therefore, I will explain fundamentally and as easy to understand as possible.

Human milk generally contains an average of 1% protein, while cow’s milk contains 3.4%. This rate is 5.5% in goat milk, 2.2% in donkey milk and 12.2% in dog milk. These ratios may not seem important. However, considering the puppies’ birth weight doubled in 9 days, a calf in 50 days and a baby in 180 days, it is understood how significant these slight differences are.

When milk proteins are mentioned, one type of standard protein should not come to mind. Milk has many different types of proteins with different structures and properties. Milk proteins can be classified as follows;

I. Casein

I.a. κ-Casein

I.b. β-Casein

1.c. αs-Casein

II. Serum proteins

II.a. albumins

II.b. Globulins (Immunoglobulins)

II.c. Proteose-peptones

III. Minor proteins

*As it is known, the most distinctive feature that distinguishes proteins from other nutrients, such as fat and carbohydrates, is that proteins contain nitrogen (N). In addition to the proteins classified above, milk also contains nitrogen-containing but non-protein components such as ammonia, urea and creatine. While 95% of the nitrogenous components in milk are proteins, 5% are non-protein components (ammonia, urea, uric acid, creatine, nitrate, free amino acids, choline and phosphatide).

Classification of milk proteins


Casein is the type of protein with the highest percentage of milk proteins (about 80% of the protein in milk is casein). It is found only in milk and dairy products. Casein is also called “milk protein” because it is found only in milk and is the predominant protein of milk.

It is interesting to note that the word “protein” was first used by Mulder in 1838, while the word “casein” was first used by Braconnet in 1830. This shows that while human beings could not understand proteins yet, we started to work on casein to understand and make sense of it.

Casein is found in the milk in a structure that we can liken to a rope or cable. This “rope” consists of four different types of casein; αs1-Casein, αs2-Casein, β-Casein and κ-Casein. Each of them has different characteristics and structures. κ-Casein is concentrated in the outermost layer of the “rope” and, unlike other casein fractions, also contains glucose. Calcium phosphate is also present in “the rope”, along with the casein fractions.

In food chemistry, this rope structure of casein is called “casein micelle.” However, it is also called “colloidal calcium caseinate,” “calcium caseinate,” “calcium caseinate-calcium phosphate,” or “caseinate miscella”. Approximately 1014-1016 casein micelles are in one milliliter (1 mL) of milk.

Casein is important in terms of the processing of milk into the product as well as nutrition. As a matter of fact, “casein micelle” can lose its structure with acid, heat, or enzyme effect and become “coagulated” in technical terms. What we call milk curdling colloquially is the coagulation of casein micelles.

This feature of casein enables us to produce foods that we call “cheese” today, which has a significant place in our diet. As a matter of fact, all other cheeses, except curd cheeses produced from whey, are actually made by coagulation of casein.

On the other hand, coagulation of casein micelles, curdling of milk, means that milk cannot be processed into products such as drinking milk, yogurt, or buttermilk.

Serum Proteins

Serum proteins are another protein group in milk and are divided into three different types; albumins, globulins and proteose-peptones. Serum proteins are more valuable in nutrition than casein because serum proteins contain high amounts of essential amino acids in their structure.

If we look at the quality of the protein types, the quality score of milk proteins on the protein quality scale is 92. This value is the average of the quality score of the protein types in the milk. Essentially, the protein quality score of casein is 73, and serum proteins are 104; a score of 92 is given as the average of the quality score of the protein species.

On the other hand, globulins, a type of serum protein, are very beneficial for the immune system and have protective effects on the immune system. Therefore, globulins are also called immunoglobulins (Ig). Immunoglobulins are present in small amounts in milk (approximately 0.8 g/litre) and very high amounts in colostrum (approximately 58 g/litre).

Serum proteins are very sensitive to heat and coagulate into fine clots when milk is heated. (Generally, at temperatures above 60oC, coagulation of serum proteins begins) However, these clots are invisible. When milk is boiled, the part that sticks to the pot is mostly serum proteins.

On the other hand, during cheese production, serum proteins do not remain in the cheese mass and are removed from the cheese along with the whey. In this context, it should be said that “curd” produced from whey has very high-quality protein. It can be noted that “curd produced from whey is the milk product with the most valuable protein.” Likewise, whey powder consumed by individuals in bodybuilding sports also contains serum proteins.

At this point, another classification for milk should be mentioned. As mentioned before, the proportions of the components in milk vary according to the mammalian species.

While the milk of some mammalian species has a higher casein content, the milk of some species has a higher albumin content. Generally, milk is called “albumin milk,” which has albumin more than 1/3 of its total protein and milk is called “casein milk,” which has casein more than 2/3 of total protein.

While human, horse, donkey and dog milk are classified as “albumin milk”; cow, sheep, goat and buffalo milk are classified as “casein milk.”

Minor Proteins

Examples of minor proteins found in milk are transferrin, lactoferrin, β2-microglobulin, and glycoprotein-α. The most important of these is lactoferrin.

Lactoferrin is a protein involved in the transport of iron. Lactoferrin, which is loaded with iron, gains an antibacterial character. Human milk contains ten times more lactoferrin than cow’s milk. The presence of excessive amounts of lactoferrin in cow’s milk is accepted as an indication that the animal from which that milk is being milked has an infection.

On the other hand, as a result of the proteolysis activity of microorganisms in milk (secreting protein-degrading enzymes and breaking down proteins), peptides of many different types and characteristics emerge.

While some of these peptides are useful and desirable, some are undesirable in taste and smell. Similarly, peptides with adverse effects on health, such as “biogenic amines,” may also occur. Peptides formed as a result of proteolysis is a very detailed subject. Therefore, it will not be discussed further in this section.

Note; Some sources also evaluate enzymes in the protein title. I and many other sources consider enzymes in the title “other components”. Therefore, the title of enzymes is given under the title of “other components.”

4. Lipids

On average, 3.7% of milk consists of fat and fat-like molecules in the lipid class. However, it should be known that this rate is highly variable and many factors are effective.

Milk fat is extremely important because of its unique flavor and high nutritional value. So much so that, in the dairy industry, the milk accepted by the factory is usually valued according to the amount of fat it contains. On the other hand, milk fat is significant because of the raw material of cream, cream, butter and ghee.

Since the density of milk fat is lower than water, a high percentage of it gathers on the surface of the milk and forms a layer we call cream.

In the dairy industry, especially in drinking milk and yogurt production, the “homogenization” technique is applied for minimizing the fat droplets volumes, preventing the fat from collecting on the surface and ensuring that the milk is evenly distributed throughout.

Lipids are the class in which fat and fat-like molecules are collected (For more detailed information on Lipids, see Lipids; Fatty acids, Fats and Oils). Milk fat contains triglycerides, diglycerides, monoglycerides, lecithin, cephalin, sphingomyelin, cholesterol, lanosterol, free fatty acids, carotenoids, vitamins A, D, E and K from the lipid class.

Triglycerides, fat molecules, make up about 99% of milk fat, while the remaining components make up about 1%. After triglycerides, the most abundant lipid type in milk is diglycerides and monoglycerides.

As it is known, triglycerides consist of the combination of a glycerol molecule with 3 fatty acid molecules, and as it is known, fatty acids can be of many different kinds.

Milk fat is the richest fat on earth regarding its fatty acid diversity. As a matter of fact, studies have found over 400 different fatty acids in milk fat. However, approximately 20-25 of them constitute 99% of the fatty acid content of milk fat, while the remaining varieties are present in trace amounts.

*Since I worked on butter in my master’s and doctoral thesis, I also determined this situation with my studies. The fatty acid composition of milk fat is quite wide. Fatty acid diversity and the characteristics and nutritional value that this diversity brings to milk fat is a very important issue, and many other points need to be clarified.

The most abundant fatty acids in milk fat are as follows;

The fatty acid profile of milk

*The average values in the table are the data I obtained in my doctoral thesis. As I mentioned before, these rates are variable. The range of variation consists of data obtained from different studies.

The fatty acid composition of milk fat is highly variable and is affected by many factors, especially the animal’s diet, season, species, breed, age and lactation period. Changes in fatty acid composition affect the structure of milk fat.

This situation is best observed in butter. As it is known, butter produced in winter is harder than butter made in summer. (Summer butter’s unsaturated fatty acid ratio is higher than winter butter’s. The melting points of unsaturated fatty acids are lower, and as the percentage of these acids increases, the structure becomes softer. This is due to the seasonal changes in animals’ diets.)

Of these fatty acids, fatty acids with less than 12 carbon atoms in their structure are volatile and are highly critical in the formation of the characteristic flavor and aroma of milk fat.

As mentioned in the “enzymes” section below, the lipase enzyme naturally found in the structure of milk breaks down triglycerides and liberates fatty acids. A small amount of free fatty acids with less than 12 carbon atoms provide the unique flavor of butter.

However, when the lipase enzyme continues its activity and the ratio of free fatty acids increases, the unwanted “bitterness,” which we call “ransite taste,” and “goat-like” taste and odor occur. Butyric acid with four carbons is responsible for bitterness, while caproic, caprylic and capric acids with 6,8 and 10 carbons are responsible for a goaty odor. Essentially, “caprin” in French means “goat.” These fatty acids likely got their name for this reason.

Fatty acids containing more than 12 carbon atoms in their structure do not affect taste and odor. Bad taste and odor formation can also be caused by β-oxidation of saturated fatty acids by enzymes produced by molds.

Another class of lipids found in milk fat is phospholipids. Lecithin, cephalin, sphingomyelin and phosphatidylcholine are the main phospholipids found in milk fat. Phospholipids are present in amounts ranging from 200 mg to 1 gram per liter of milk. Although relatively few in amount, phospholipids have very important for body functions.

As a matter of fact, phospholipids are one of the primary building materials of bone, brain, nervous tissue, heart muscles, liver and sperm. Phospholipids can also be produced in the body, but studies have shown that dietary lecithin can help improve learning ability, strengthen memory, and effectively heal nervous disorders.

The main sterol found in milk fat is cholesterol. Apart from that, small amounts of lanosterol and 7-dehydrocholesterol are found. While there are about 15 mg of cholesterol in 100 mL of cow’s milk, it can be found between 10-40 mg in human milk. The importance of cholesterol in terms of health and nutrition is mentioned under the title of “Milk and Nutrition; Nutritional value of milk.”

Free fatty acids are released also due to the breakdown of glycerides, or by the effect of mechanical processes applied to milk as well as in the natural structure of milk. As mentioned before, the presence of free short-chain fatty acids in milk has a significant impact on taste and flavor. While a certain amount of these fatty acids provides the desired flavor, excess of this amount causes an undesirable taste.

Another group of lipids found in milk are carotenoids. β-carotene is the most abundant carotenoid in milk and is important in two respects. First, β-carotene can be converted to vitamin A in the body. Therefore, it is of great importance in terms of nutrition. Because of this feature, another name for β-carotene is provitamin A. Secondly, β-carotene is a coloring substance particularly effective on butter’s “yellow” color.

Squalenes and waxes, other classes of lipids, are found in trace amounts in milk.

Note: Vitamins A, D, E and K are lipid molecules and should be included under the lipid heading. However, it has been examined under the title of vitamins to provide a more comprehensive expression.

5. Minerals

On average, cow’s milk contains between 0.7% and 0.9% of minerals. This value represents the amount of ash remaining from the incineration process. The amount of ash also includes sulfur and phosphorus in the structure of proteins, as well as oxides and carbonates remaining from organic salts, citrates and carbon dioxide, in addition to the minerals present in the serum phase of the milk as ions.

This means; for example, methionine, the amino acid, contains sulfur, and methionine is often used as a building block in the body without being broken down. Therefore, it is not rational to consider the sulfur left over from methionine as a “mineral that the body can benefit from.” The fact is that sulfur is not used as a mineral by the body in its free ion form.

However, the majority of the ash amount is “mineral usable by the body.” Therefore, the amount of ash is generally used to express the mineral substance content.

The mineral content of milk is affected by many factors and is, therefore, highly variable. The most abundant minerals in milk are potassium, calcium, chlorine, phosphorus, sodium and magnesium. Iron, zinc, aluminum, copper, nickel, cobalt, iodine, fluorine, molybdenum and manganese are minerals found in trace amounts in milk. The average amounts of minerals found in cow and human milk are given in the table below;

The mineral content of milk

As mentioned earlier, minerals can vary considerably depending on many factors. These factors include race, species, disease, season, and diet. For example, the Jersey breed contains more calcium and phosphorus in its milk than the Holstein breed.

When dairy products are evaluated in terms of minerals, the amount of mineral substances in cheese is relatively high compared to milk. The main reason is that cheese becomes a more concentrated food because it contains less water than milk.

Another reason is the addition of calcium in the form of calcium chloride (CaCl2) to give structure and the addition of salt (NaCl) for flavor to milk during cheese production. In this case, the amount of calcium, sodium and chlorine in cheese increases significantly.

Heat treatment applied to milk causes the calcium in the structure of casein to pass into the serum phase. Adding calcium to milk is an essential process to obtain a cheese. For this purpose, 200 grams of calcium chloride is usually added to 1 ton of milk. On the other hand, salt is usually around 4% in cheese, although the salting method is different.

6. Vitamins

Milk is very rich in vitamins, but the fact that vitamins are sensitive components and suffer a severe loss during the applied processes prevents us from fully benefiting from vitamins. Vitamins are susceptible to heat and light and suffer severe losses when exposed to these factors.

The vitamin content of milk

There is no question of a person consuming cow’s milk raw; the milk needs to be boiled or pasteurized. In this case, more or less loss of vitamins occurs and the expected benefit cannot be fully achieved.

The most obvious example of this situation is vitamin C. Vitamin C is the most abundant vitamin in milk. However, unfortunately, same time, one of the most heat-sensitive vitamins is vitamin C and its structure brokes up to 90% depending on the degree of heat treatment.

From this point of view, although vitamin C is the most abundant vitamin in milk, it is not possible to consider milk as a source of vitamin C. However, there is no loss of vitamins with breastfeeding.

Another vitamin affected by heat treatment is vitamin B12. While there is a 30-50% loss in vitamin B12 with boiling, this loss is around 10% in pasteurized and UHT milk.

Besides heat and light, another vitamin loss causes are interaction with heavy metals or oxygen.

On the other hand, when dairy products are examined in terms of vitamins, it is seen that butter contains high amounts of fat-soluble vitamins A, D, E and K. Similarly, high-fat cheese varieties contain higher amounts of these vitamins than milk.

7. Other Components

Organic acids

The primary organic acids found in milk are citric acid and lactic acid. Citric acid makes up about 90% of total acids.

Citric acid is very critical for the stability of the casein. In the presence of sufficient citric acid in milk, casein does not coagulate during heat treatment. Citric acid is present in milk at 0.9-2.3 grams/liter. The milk of grass-fed animals contains less citric acid, while the green-grass-fed milk contains more.

Lactic acid is another critical component for the stability of milk. Under normal conditions, it is accepted that newly expressed milk does not contain lactic acid. However, lactic acid is formed due to the microorganisms in the milk breaking down the lactose over time, and the amount increases as this situation progresses.

The accumulation of lactic acid in milk threatens the integrity of the casein. When the amount of lactic acid reaches a certain level (approximately 6 grams per liter), casein coagulates when milk is heated, which we observe as “milk curdling” when boiling milk at home. When the lactic acid amount is too high (approximately 10 grams per liter), the milk coagulates without needing heat treatment.

Other organic acids found in milk are neuramic acid, pyruvic acid, uric acid, orotic acid, deoxyribonucleic acid (DNA), ribonucleic acid (RNA), benzoic acid, hippuric acid, indoxyl sulfate and α-liponic acid.


Carbon dioxide (CO2), oxygen (O2) and nitrogen (N2) gases constitute approximately 7% of milk by volume. The most abundant gas in milk is carbon dioxide. A liter of milk contains an average of 100 mg of carbon dioxide, 15 mg of nitrogen and 7.5 mg of oxygen gas. As a result of the activities of microorganisms in milk, the amount of carbon dioxide increases.

While carbon dioxide and oxygen have significant effects on the properties of milk, nitrogen has no positive or adverse effects. Carbon dioxide and oxygen have a positive impact on the flavor of milk. On the other hand, the presence of oxygen triggers oxidation and causes losses in vitamins A, E and C. Similarly, oxidation of unsaturated fatty acids causes bitterness.


Enzymes are components with a protein structure, and while some sources classify enzymes as other components, some authorities classify them as proteins. Although enzymes are components in protein structure, since their functions are more critical than their structure, it is necessary to evaluate enzymes not in protein class but in other components class. That’s why I considered the enzymes in “other components.”

Approximately 60 types of enzymes in milk pass through the animal in which it is milked. The main enzymes found in milk are lysozyme, lactoperoxidase, lipase, alkaline phosphatase, protease, ribonuclease and xanthine oxidase.

The lactoperoxidase enzyme has an antibacterial effect against some microorganisms and is important in this respect. However, it should be noted that this effect is quite limited.

The enzyme lysozyme has a similar antibacterial effect. The enzyme lysozyme is found in high amounts in camel milk and the antibacterial effect of lysozyme is more pronounced in camel milk.

Lipase enzyme is the factor that causes bitterness (ransite taste), especially during cold storage of butter. The fact that it does not lose its activity even at -40oC causes this effect. Lipase breaks the bond between glycerol and fatty acids in the triglyceride molecule and liberates the fatty acids.

Another important enzyme naturally found in milk is alkaline phosphatase. It loses its alkaline phosphatase activity at pasteurization temperature. Due to this feature, alkaline phosphatase test is applied to determine whether pasteurization is done in the industry or is done effectively.

A positive result of the alkaline phosphatase test means that pasteurization doesn’t occur or isn’t done effectively. Another possibility is that pasteurized milk was mixed with unpasteurized milk.

Proteases can be found in the natural structure of milk or produced by microorganisms found in milk. Proteases produced by psychotropic bacteria (bacteria that grow in cold, such as Pseudomonas fluorescens) in milk that has been kept in the cold (4-7oC) for a relatively long time are extremely heat resistant and cause severe problems in the production of UHT milk and cheeses. Proteases produced by psychotrophic bacteria cause gelation in UHT milk, undesirable bitterness in aged cheeses and loss of efficiency in fresh cheeses.


Since some of the hormones are involved in milk production in the udder, they pass into the milk, albeit in a small amount (at the level of nanograms-10-9 grams per milliliter and picograms-10-12 grams) during production. However, it should be noted that the amounts of these hormones are very low and therefore have no effect on human metabolism and are insignificant.

The main hormones in milk are estrogens, prolactin, progesterone, cortisol, prostaglandins and somatotropin.

Somatotropin (STH), one of these hormones, has industrial importance and is used effectively in dairy cattle. Up to 40% increase in milk yield can be achieved by injecting STH into the animal.

Somatic cells

Somatic cells are epithelial cells that pass from the mammary tissue of the animal and leukocytes, erythrocytes and lymphocytes that pass from the blood to the milk. In general, there are 10,000-400,000 somatic cells in 1 milliliter of milk, which is natural.

As a result of infection in the animal’s udder, the number of somatic cells that pass into the milk increases. Especially in mastitis disease, the number of somatic cells in milk may reach up to 1 million units/mL. Of course, when these numbers are reached, milk is no longer milk and its structure, taste and appearance become unacceptable.

In this context, control of somatic cell numbers becomes extremely important. Mastitis, also known as mammary inflammation, is a disease frequently seen with the effect of heat, especially in summer, and can be transmitted to other animals quickly if it is not controlled.

In the first stages of mastitis, although the milk quality changes a little, if no precautions are taken, the milk quality becomes unacceptable and It causes effects that can lead to atrophy of the udder. As a result, it can cause decreases in both quality and yield. Somatic cell count is the most critical parameter in the control of mastitis.

Most countries have set limits on the number of somatic cells. In the European Union and Turkey, the condition that the milk to be accepted into the business must have a maximum of 400,000 units/mL of somatic cells, which is 750,000 units/mL in the United States.

If I’m not mistaken, it was 2008 and I was interning at a dairy farm. The farm with 650 dairy animals had an average somatic cell count of 250,000/mL, and I struggled to cope with mastitis. While I was busy administering CMT (California Mastitis Test) to every udder of 650 animals, milk from a farmer subordinate to us had an average somatic cell count of 8,000/mL in mid-July.

This situation aroused great curiosity, and I asked the milk-collecting worker, “Who is this peasant farmer?” The worker told me, “That farmer is an agricultural engineer.” For me, this was an indicator of how effective and valuable it is to do your job deliberately.


Microorganisms are not generally classified as a component of food. However, although in insignificant amounts by mass, they are of the utmost importance in terms of effect and should be considered a component of foods from this point of view.

Dairy microbiology is a vast subject, and since it will disintegrate the topic here, “Microorganisms Found in Raw Milk; Types, Effects and Importance” is explained in detail in the article.

Foreign Matters

What foreign matter mean in milk is to express substances that are not in the nature of milk and should not be present in milk.

The main foreign matters found in raw milk are visible coarse dirt. We see this in our homes when we run raw milk through a cheesecloth or cloth before boiling it. In the dairy industry, coarse dirt is removed with devices called “clarificator.”

Another foreign matter that can be found in milk is metals. When accumulates enough lactic acid in milk after a certain period, it becomes corrosive to metal equipment. Due to this effect, using aluminum tools, equipment and jugs in the dairy industry is prohibited.

Another contamination way of metals is the water used in the business. Therefore, specific standards exist on the metal ions and concentrations that the water used in the dairy industry may contain.

Substances such as detergents and disinfectants may also be found in raw milk if an effective rinsing is not performed during the cleaning of the dairy.

Pesticides, antibiotics and aflatoxin are the most important foreign matters that should not be present in milk.

As it is known, pesticides are substances used in feed agriculture to protect plants against harmful organisms. These substances can also pass into the milk of animals fed with feed containing these substances. There are very serious inspections and standards on pesticides.

Pest control drugs applied to barns or animals to protect animals from lice and ticks can also pass through the skin and blood of the animal into the milk. Therefore, when the barn is applied, the times when the animals are not inside should be chosen and the animals should be taken inside after the barn is ventilated for a while.

Antibiotics are administered to the animal for treatment when the animal is sick. However, these applied substances can pass into the milk of the animal. The presence of antibiotics in milk makes it impossible to process milk into a fermented product such as yogurt and is extremely harmful to human health (Presence of antibiotic in milk is one of the major reason for the development of antibiotic resistance).

 Therefore, the animal’s milk treated with antibiotics is not used and consumed unless 72 hours have passed since the last dose. During this process, milk is milked, but it is discharged to the sewer.

On the other hand, Aflatoxins are toxins produced by some mold species in feed if feeds are not stored properly. These toxins also pass into the milk of the animal consuming the meal. Aflatoxin is a carcinogenic substance and its control and standard are very strict.

Unlike these, substances such as carbonate or hydrogen peroxide, which are added for cheating, are unfortunately sometimes found. The use of these substances is, of course, prohibited and subject to penalties.


In the structure of milk, besides all these components, there is also a tiny amount of defined or unidentified molecules. But, in terms of expressing the general scope, the given components are sufficient.

Milk and Nutrition; Nutritional Value of Milk

Only two foods on earth can be sufficient for a living thing to come into existence or for a newborn creature to grow and develop; milk and eggs. The egg contains all the food necessary for the fertilized egg cell to become a chick.

Similarly, milk contains all the components that a newborn creature needs to grow and develop and continue its life activities. From this point of view, it is understood that milk and eggs have all the building blocks that a living thing needs.

Seeds (grains and legumes) are the foods closest in nutrition to eggs and milk. The seed’s nutrients are sufficient for its embryo to become a complete sprout. Its embryo needs only water, besides the nutrients it provides from the seed.

However, the components required by animals and plants for their formation and development differ, and it should be taken into account that the human race has a metabolism closer to animal metabolism. From this point of view, milk and egg are one step ahead.

Milk can be consumed as drinking milk, and it is also extremely important as it is the main raw material of foods such as yogurt, cheese, kefir, ice cream, or butter. In particular, foods such as village-type yogurt, cheese, kefir or butter containing probiotic microorganisms add value to the value of milk. Or a unique food such as moldy cheese is produced by using milk as a raw material.

Incidentally, some plant milk, such as almond and coconut milk, which have become popular recently, have nothing in common with milk other than appearance. These foods are commercial products for vegan individuals, with a completely different structure and composition than milk.

The protein contained in milk is precious in terms of nutrition. As a matter of fact, milk proteins are very high-quality proteins. This quality is because milk proteins have all of the essential amino acids (amino acids that cannot be produced in the body and must be taken from the diet) at a sufficient level.

On the scale where the quality of egg proteins is evaluated as 100 points, the quality of milk proteins is 92 points. (The quality score of wheat flour protein is 45, potato is 69, and beef is 78. For more detailed information, see Proteins; Functions in the Body, Quality and Daily Needs )

Among the amino acids that function in human metabolism, only hydroxyproline is not present in the structure of milk proteins. Hydroxyproline can already be produced in the body and is not an essential amino acid.

The fatty acid richness of milk fat has been mentioned before. Indeed, when viewed as fat, milk fat is very valuable because it also contains essential fatty acids. Therefore, foods such as butter made from milk fat, cream and ghee (the traditional butter of India) are also precious fats. (For detailed information on butter, see All About Butter; Composition, Properties and Health Benefits)

Although it is stated that fats cause weight gain, consumption of essential fatty acids is mandatory for the body. Therefore, even if you are on a diet, consuming 20-60 grams of fat daily is beneficial, depending on the body. Butter and olive oil are the good options for oil consumption. (For more detailed information on the nutritional importance of fats, see Fats and Oils; Functions in the Body and Daily Needs)

From the 1970s to the beginning of the 2000s, there was a lot of news that milk fat and especially butter were unhealthy, but this was a great injustice. As a matter of fact, in the 2000s, the reputation of milk fat and butter was restored and they were declared to be healthy.

The cover of the 183rd issue of Time magazine, published on June 23, 2014, headline is “Eat butter!”

*source; time magazine

The feared side of milk, especially butter, was that it contained cholesterol and could cause heart and vascular diseases. However, cow’s milk and butter do not have high cholesterol. Approximately 15 mg cholesterol contains 100 mL milk; 100 grams butter contains around 250 mg of cholesterol.

In other words, if you drink a glass of milk, you will take approximately 30 mg of cholesterol; if you consume an average of 20 grams of butter a day, you will take an average of 50 mg of cholesterol to the body. The recommended daily take limit of cholesterol is 300 mg per day. Therefore, it is not possible to approach the daily cholesterol consumption limit with an ideal milk and butter consumption.

Whereas for decades, people were frightened by it, and for years they were estranged from the wonderful nutritiousness of milk and butter.

Lactose is broken down in the digestive system by the enzyme lactase. Some individuals may have the absence or deficiency of the lactase enzyme. When these individuals consume milk or dairy products containing lactose, they cannot digest lactose and some health problems occur, such as bloating, stomachaches and diarrhea. This condition is called “lactose intolerance.”

Lactose-free milk and dairy products for lactose-intolerance individuals are found on the market today. In fact, these products are products whose lactose is broken down by adding lactase enzyme.

Since glucose and galactose molecules occured when lactose is broken down are sweeter than lactose, these “lactose-free” products feel sweeter than standard products. Essentially, calling these products “lactose-cracked” is more consistent than “lactose-free“.

Milk is a food rich in vitamins. The necessity of consuming milk after heat treatment causes a loss in vitamin content. However, pasteurized, UHT, or boiled milk is rich in B12, B2, B1, Pantothenic acid, and Folic acid and is precious in terms of nutrition. (For detailed information on vitamins, see All Vitamins; Functions, Daily Needs and Rich Foods)

However, if milk is drunk directly from the mother through breastfeeding, it is possible to fully benefit from vitamins, since there is no loss. For example, a newborn calf receives full vitamin benefit from the milk it sucks from the mother cow. Likewise, the baby fully benefits from the vitamin in the breast milk.

In terms of minerals, it is known by almost everyone today that milk and dairy products are calcium-rich foods. In particular, the amount of calcium in cheese is 5-6 times higher than in milk. On the other hand, calcium absorption in yogurt is higher than in milk.

In addition to calcium, milk and dairy products are good sources of also phosphorus, magnesium, iodine and zinc. (For detailed information on minerals, see All Minerals; Functions, Daily Needs and Rich Foods)

In conclusion, milk is a miraculous food that nature offers us. Its composition is rich and in terms of nutrition, it is an excellent food. Milk obtained from healthy animals by conscious producers and kept under the right conditions is extremely valuable.

Although some experts have expressed negative opinions against UHT and pasteurized milk recently, it should be known that UHT and pasteurized milk are also very healthy and nutritious products. On this subject, I wrote an article titled “Raw Milk, Pasteurized Milk or UHT Milk?” I recommend that you read my article.

I dedicate this article to my Ph.D. supervisor, dear Prof. Dr. Mustafa ŞENGÜL. With endless gratitude…

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