Milk has five nutrients: protein, fat, carbohydrates, vitamins and inorganic salts.

I.? Supply life nutrition protein

Milk contains about 3.5% of the protein (human milk about 1.25%), which is casein-based, followed by milk white eggs and lactoglobulin. They all contain all the essential amino acids of the human body, and their relative content is similar to that of egg protein, with a higher digestibility of 96.1%. Casein accounts for about 86% of the total amount of protein, lactalbumin accounts for about 9% of the total amount of protein, lactoglobulin accounts for about 3% of the total amount of protein, and other serum white, immunoglobulin and enzymes.

Two, the human body energy carrier fat

Milk contains fat 3.4% -3.8% (human milk contains about 3.7%), is a microscopic fat particles (diameter 2-5μm) highly dispersed in the milk, so it is easy to be digested by the human body, and its digestibility of 97%. The composition of the fat is dominated by saturated palmitic acid and stearic acid, accounting for about 40%, saturated short-chain fatty acids such as butyric acid and has been about 9.0%, unsaturated oleic acid accounted for 30%, linoleic acid and linolenic acid accounted for only 3.0%, and the rest of the lauroic acid and myristic acid and so on.

Three, regulating metabolic vitamins

The content of vitamins in milk is related to the feed of cows, cows eat more grass in the summer, so milk vitamin A content is also higher. Summer sunshine time is long, the content of vitamin D is higher. Each 100g of milk contains riboflavin 160μg, thiamin raise 45μg. milk vitamin C, vitamin D content is not much, so the milk as food for infants to pay extra attention to vitamin C, vitamin D supplementation or fortification of milk.

Four, involved in a variety of cellular activities of carbohydrates

Milk carbohydrates are mainly lactose, the content of 4.6% -4.7%, compared with human milk lactose (content of 7.0% -7.8%) less, milk feeding infants, can be diluted and add the appropriate amount of sucrose, to ensure that adequate caloric energy, and human milk equivalent sweetness and protein. Lactose has the effect of regulating gastric acid, promoting gastrointestinal peristalsis and secretion of the digestive glands, promoting the propagation of certain lactic acid bacteria in the intestines and inhibiting the growth of spoilage bacteria. It can also provide heat energy and promote the absorption of metal ions such as calcium, magnesium, iron, zinc, etc., which is very important for the intellectual development of infants, in addition to the degree of absorption of calcium is directly proportional to the amount of lactose, rich in lactose content, can play a role in preventing rickets.

Fifth, inorganic salts involved in the metabolism of substances in the body

Cow's milk contains inorganic salts 0.7% -75%, goat's milk is 0.9%, and especially rich in calcium, phosphorus, potassium. 1L of milk can provide 1g of calcium, and the ratio of calcium and phosphorus in milk is 1.2:1, close to human milk (human milk is 1:1), high rate of digestion and absorption, so it ensures that infants on the needs of calcium. Iron in milk is very little, only 0.2mg/100g, 1/5 of human milk, milk-based feeding of infants, but also need to add iron and vitamin C-containing foods in a timely manner for supplementation, such as egg yolks, pureed liver, pureed vegetables and so on. In addition, milk also contains copper, zinc, manganese, iodine, molybdenum and other trace elements.

Extended information:

Nutritional value of milk

Milk contains carbohydrates in which the most abundant is lactose, which makes calcium easily absorbed.

Milk contains good quality proteins, including casein, a small amount of whey protein, whose biological value is 85. Milk includes all the amino acids needed for human growth and development, which is incomparable to other foods.

Milk has a reasonable ratio of protein to calories, which ensures that the drinker does not consume "pure" calories.

The calcium content of milk is easily absorbed, and the combination of phosphorus, potassium, magnesium and other substances is also very reasonable.

The fat contained in milk has a low melting point, small particles, and is easily digested and absorbed by the human body, and its digestibility reaches 97%.

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