The chemical composition of milk is very complicated, with at least 100 species. The main ingredients are water, fat, phospholipids, protein, lactose and inorganic salts. The main chemical components of ordinary milk are:
There are 20 kinds of amino acids that make up human protein, 8 of which are not synthesized by human body. These amino acids are called essential amino acids. If the protein we eat contains all the essential amino acids, this protein is called total protein. Protein in milk is whole protein.
Inorganic salts in milk are also called minerals. Milk contains cations such as Ca2+, Mg2+, K+ and Fe3+ and anions such as PO43-, SO42- and Cl-. In addition, there are trace elements I, Cu, Zn, Mn and so on. Most of these elements play an important role in human development, growth and metabolic regulation. Calcium is the most abundant inorganic salt in human body and the main component of bones and teeth. 90% of calcium in human body is concentrated in teeth and bones. Children and adolescents need adequate calcium for their growth and development, as do pregnant women, adults and middle-aged and elderly people. Calcium deficiency will affect the normal development of teeth and bones, leading to rickets. Calcium in nature exists in a bound state. Only when it is passively absorbed by plants to form bioactive calcium can it be better absorbed and utilized by human body. Milk is rich in active calcium, which is one of the best sources of calcium in human body. 1 l fresh milk contains about1250mg of active calcium, ranking first among many foods, which is about 10 1 times of rice, 75 times of lean beef and10/0 times of lean pork. Good absorption is especially critical for calcium supplementation. Therefore, the saying that "milk can supplement calcium" has its scientific reason.
For middle-aged and elderly people, milk also has a great advantage, that is, compared with the high cholesterol of many animal proteins, the cholesterol content in milk is lower (milk:13mg/100g; Lean meat: 77 mg/100 g). It is worth mentioning that some ingredients in milk can also inhibit the amount of cholesterol produced by the liver, so milk can also lower cholesterol.
Second, the consumption of dairy products in countries around the world and China
In fact, before China put forward the "Student Drinking Milk Plan", many countries and nations regarded milk as a magic weapon to improve their physical fitness. At present, a global "school milk plan" is being launched around the world. When talking about the reconstruction of Europe after World War II, former British Prime Minister Winston Churchill once said: "Nothing is more important than providing milk to children!" . After World War II, the Japanese even put forward the slogan "A glass of milk makes a nation strong", which greatly improved the physical quality of the post-war generation. Historically, American residents have also solved the problem of calcium nutrition through the "three cups of milk" campaign. Dairy products have become the main food for westerners.
At present, the average annual consumption of dairy products in the world is 100kg, while that in China is only 6 kg, which is less than one tenth of the world average. This is related to China people's eating habits and their understanding of milk. To this end, we launched a survey. The subjects of the survey are mainly the parents of classmates around them and some of their neighbors and relatives (attached: questionnaire), which can not represent all of them, but it can also explain the problem to some extent. The survey results show that in the past 80% families did not drink milk often, and 20% families never even drank milk. Only 20% families have the habit of drinking milk. Many families said that they only used milk as their children's staple food in infancy, and then they stopped emphasizing drinking milk when they were a little older. Regarding the question "How do you supplement your children's nutrition?", 60% of parents choose to buy expensive nutrition and health care products, and 75% choose to buy some advanced foods. Only less than 10% of parents choose to give their children a glass of milk every day. These are mainly due to ignorance of milk nutrition. Do you know the nutritional value of milk? In the answer, 30% "do not know"; 60% "know a thing or two"; Only 10% "knows".
Third, how to buy dairy products?
Since dairy products are a kind of food that can accompany human life, how to choose and drink them correctly is also worthy of attention. At present, dairy products in the domestic market can be roughly divided into two categories. One is liquid milk, including sterilized milk, ultra-high temperature sterilized milk, yogurt and lactic acid beverage. The other is milk powder.
Liquid milk is mainly fresh milk, and it is also one of the most popular dairy products for consumers. According to the survey, 60% people like to drink fresh milk. Since it is fresh milk, it is expensive in a fresh word. Its freshness and quality inspection are particularly important. The survey also found that many people don't know how to identify and choose. Here are some simple ways to identify the freshness of fresh milk:
Methods 1 Sensory identification: fresh milk (sterilized milk) is milky white or yellowish, with the inherent fragrance of fresh milk, no peculiar smell, uniform liquid, no precipitation, no coagulation, no impurities, no foreign bodies and no stickiness.
Method 2: Drop milk into clear water, and it will be fresh milk if it does not melt; If it melts, it is not fresh milk. If it is bottled milk, it is not new milk as long as thinning phenomenon is observed on the upper part of the milk or precipitation is observed at the bottom of the bottle.
Method 3: Boiling test: Take about 10ml milk sample in a test tube (or a transparent glass) and put it in boiling water for 5 minutes to observe. If there is coagulation or floc, it means that the milk is not fresh or has gone bad.
Fourth, drink milk scientifically.
Everyone knows that drinking milk is good, but there are many stresses about drinking milk. If you don't drink it properly, milk will not only help your health, but also cause some harm: