I. protein and protein peptides
The content of protein in milk is 3.0-3.5g/ 100g. Because its amino acid composition ratio is very close to that of protein synthesized by human body, and its digestion and absorption rate is as high as 98%, it is considered as one of the protein with the highest nutritional value.
There are four kinds of milk proteins: β-lactoglobulin, γ-whey protein, whey protein and casein. Among them, casein contributes the most to milk protein, accounting for 80%, and contains 10% phosphorus, which plays a vital role in promoting brain development; Whey protein molecules are smaller than casein and easier to digest; Lactoglobulin is mostly bioactive substances in milk, such as immunoglobulin, lactoferrin and lysozyme.
Immune substances in milk are mainly immunoglobulins, including IgG, IgA and IgM, among which IgG is the most abundant. It has the ability to resist invading pathogens such as bacteria and viruses, and can activate immune response in vivo and resist external factors. In addition, immunoglobulin in milk also helps to regulate intestinal flora and maintain intestinal health. The immunoglobulin content of bovine colostrum is the highest in all milk.
In addition, milk also contains a small amount of peptides, whose molecular weight is much smaller than that of milk protein, which is the enzymatic hydrolysis product of natural milk protein. This is an active factor with health care function in milk, for example, it can promote the growth of Bifidobacterium and regulate the immune response of the body, thus having a health care effect on the body.
Second, fats and fatty acids.
The fat content in whole milk is 3.0-3.5g/ 100g, and its fatty acid composition is dominated by medium-chain fatty acids, which is very easy to digest and absorb. The disadvantage is that the content of polyunsaturated fatty acids (PUFAs) in total fatty acids is very low, which will have adverse effects on the body. Therefore, people with hyperlipidemia should control the intake of milk fat, mainly skim milk.
But the fat in milk plays a great role: all the aroma components exist in milk fat, and skim milk has no milk fragrance; Secondly, both fat-soluble vitamins A and D in milk contain fat, which greatly improves the health of the body. In addition, conjugated linoleic acid contained in milk has a positive effect on inhibiting cancer and preventing diabetes.
Third, carbohydrates and functional sugars.
The carbohydrate content in milk is 4.5~5.0g/ 100g, of which more than 95% is lactose. This is a disaccharide, which is the best carbohydrate that can be absorbed and utilized in the early life of human beings. With the growth of age, grains have played a role in providing the main source of carbohydrates for the human body, and lactose in milk has just withdrawn from the stage. However, lactose can promote calcium absorption.
Milk also contains a small amount of other sugars and oligosaccharides, such as galactose, sialyllactose, lactose -N- neotetraose and so on. These sugars can participate in the synthesis of glycoprotein or other components on the surface of intestinal cells, and play a role in inhibiting the combination of intestinal pathogens and intestinal cells, thus achieving the role of protecting the body.
There are many other ingredients in milk. With the deepening of its research, people will find more and more new functions of milk. Of course, it does not rule out that it is not suitable for some people, such as milk with high fatty acid saturation, and it is not suitable for patients with hyperlipidemia. Therefore, it is necessary for nutritionists to popularize food nutrition knowledge and let consumers make more targeted choices.
Article editor: ugeri
Article source: