The first is protein, which provides life and nutrition.
Milk contains about 3.5% protein (human milk is about 1.25%), in which casein is the main component, followed by white eggs and lactoglobulin. They all contain all amino acids necessary for human body, and their relative content is similar to that of egg protein, with high digestibility of 96. 1%. Casein accounts for about 86% of total protein, whey protein accounts for about 9% of total protein, lactoglobulin accounts for about 3% of total protein, and others include serum albumin, immunoglobulin and enzyme.
Second, the fat of human energy carrier.
Milk contains 3.4%-3.8% fat (about 3.7% in human milk). Fat is highly dispersed in milk as fine fat particles (2-5μm in diameter), so it is easy to be digested and absorbed by human body, and the digestibility reaches 97%. Fat is mainly composed of saturated palmitic acid and stearic acid, accounting for about 40%, saturated short-chain fatty acids such as butyric acid and caproic acid account for about 9.0%, unsaturated oleic acid accounts for 30%, linoleic acid and linolenic acid only account for 3.0%, and the rest are lauric acid and myristic acid.
Third, vitamins that regulate metabolism.
The vitamin content in milk is related to the feed of dairy cows. In summer, cows eat more grass, so the vitamin A content in milk is also higher. In summer, the sunshine time is long and the vitamin D content is high. Every 100g milk contains 160μg riboflavin and 45μg thiamine. The content of vitamin C and vitamin D in milk is not much, so babies who eat milk should pay special attention to the supplement of vitamin C and vitamin D or strengthen milk.
4. Carbohydrates involved in various cell activities
The carbohydrate in milk is mainly lactose, and its content is 4.6%-4.7%, which is less than that in human milk (7.0%-7.8%). When feeding milk to infants, appropriate dilution and sucrose can be added to ensure sufficient heat energy, which is equivalent to the sweetness and protein of human milk. Lactose can regulate gastric acid, promote gastrointestinal peristalsis and digestive gland secretion, promote the reproduction of some lactic acid bacteria in the intestine and inhibit the growth of spoilage bacteria. It can also provide heat energy and promote the absorption of metal ions such as calcium, magnesium, iron and zinc, which is very important for the intellectual development of infants. In addition, the absorption of calcium is directly proportional to the amount of lactose, and rich lactose content can prevent rickets.
5. Inorganic salts participate in substance metabolism in human body.
Milk contains 0.7%-75% inorganic salts and 0.9% goat's milk, especially rich in calcium, phosphorus and potassium. 1L milk can provide 1g calcium, and the ratio of calcium and phosphorus in milk is 1.2: 1, which is close to human milk (human milk is 1: 1), and the digestion and absorption rate is high, which can ensure the baby's need for calcium. The iron content in milk is very small, only 0.2mg/ 100g, which is 1/5 of human milk. Feeding your baby with milk as the staple food requires timely supplementation of foods containing iron and vitamin C, such as egg yolk, pork liver paste and green vegetable paste. In addition, milk also contains trace elements such as copper, zinc, manganese, iodine and molybdenum.