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:

Humidity: 87.5%

Fat: 3.5%

Protein: 3.4%

Lactose: 4.6%

Inorganic salt: 0.7%

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".

The lack of knowledge makes people generally think that milk is only a dispensable food, and the consumption of dairy products is seriously insufficient, which directly leads to the serious shortage of daily dietary calcium intake of Chinese residents. The results of many nutritional surveys show that the average daily dietary calcium intake of Chinese residents is only about 400 mg, while the average daily dietary calcium intake recommended by the World Health Organization is 800- 1200 mg, which is two to three times that of China. At the same time, the survey shows that the calcium intake of infants, children, teenagers, middle-aged and elderly people, pregnant women and other people who need calcium most is also less than 60% of the standard. This shows that residents in China are generally short of calcium. Calcium deficiency will not only lead to rickets, osteomalacia, senile osteoporosis and other common diseases, but also affect the full development of bones.

Teenagers are an important period for the healthy growth of life. During this period, a reasonable diet and adequate nutrition will surely lay a good foundation for future physical and intellectual growth. Give your child 250 ml of fresh milk or 30-40 g of milk powder every day. 300 mg of calcium, 7-8 g of high-quality protein and quite a few trace elements can be obtained. If we persist in this way, the child's physique, physical quality and intellectual development will be fundamentally changed in 5 to 10 years or longer.

Fortunately, our survey results also show that in recent years, with the improvement of people's living standards and the deepening of health awareness, people have gradually realized the nutritional value of milk under the propaganda of various media, and more and more families have begun to consciously incorporate milk into their daily recipes like my family. For the sake of health, the habit of a glass of milk every day for the whole family is taking shape. We also specially visited several supermarkets and asked about the sales of dairy products. They all said that the sales of dairy products, especially fresh milk, have been rising in the past two years. Fresh milk that just arrived in the afternoon is usually sold out at noon the next day. According to the prediction of experts from China Dairy Industry Association, the consumption of dairy products in China will increase substantially in the next five years, and the annual growth rate is expected to reach more than 15%.

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.

In addition, we should pay attention to the difference between pure milk and milk-containing drinks: pure milk is also called fresh milk, pure fresh milk. As can be seen from the ingredient list of the product, there is only one ingredient in this product, namely fresh milk. There are two main indexes to distinguish the quality of pure milk: total dry matter (also called whole milk solids) and protein. The contents of these two indicators are generally stated on the packaging bag of the product. The higher their content, the higher the nutritional value of milk, and generally speaking, the higher the price. In addition, yogurt popular with consumers is fermented from pure milk, so yogurt is also pure milk.

Milk-containing drinks are allowed to be mixed with water. As can be seen from the ingredient list, in addition to fresh milk, the ingredients of this milk beverage generally include water, sweeteners, fruity agents and so on. And water is often ranked first (the state requires the ingredients in the ingredient list to be listed in the order from high to low). According to the national standard, the milk content of milk-containing beverages should not be lower than 30%, that is to say, the water content should not be higher than 70%. Because milk-containing beverage is not made of pure milk, its nutritional value cannot be compared with pure milk.

It is worth noting that there are some vague names such as "active milk" and "fresh milk" written in big letters on the packaging bags of milk-containing drinks in the market. If you look closely, you will find that there is a line of small print "milk-containing drinks" next to it, but there is not even this line of small print for individual products. Only one "water" is added to the ingredient list, which needs to be read carefully to distinguish clearly.

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:

1, don't drink raw milk, drink fresh milk and heat it at high temperature to prevent the disease from entering the mouth;

Some people are used to drinking milk on an empty stomach, which is unscientific. Because eating on an empty stomach will make the intestines move quickly. And the protein in milk will be quickly converted into energy and consumed. Nutrients in milk can't be digested and absorbed, so they are discharged into the large intestine, which virtually causes waste. It's best to eat something before drinking milk or drink it while eating.

3. 80% protein in milk is casein. When the pH value of milk is lower than 4.6, a large amount of casein will agglutinate and precipitate, which is difficult to digest and absorb, and even lead to indigestion or diarrhea in severe cases. Therefore, it is not advisable to add acidic drinks such as fruit juice to milk.

Some people like to take medicine with milk instead of boiled water. In fact, milk obviously affects the human body's absorption of drugs. Milk is easy to form a covering film on the surface of drugs, which makes calcium, magnesium and other minerals in milk react with drugs to form water-insoluble substances, thus affecting the release and absorption of drug effects. Do not drink milk before and after taking the medicine 1 hour.

5, it is not appropriate to drink more cold milk, because cold milk will affect gastrointestinal peristalsis, causing mild diarrhea, so that most of the nutrients in milk can not be absorbed and utilized by the human body.

6. It is not advisable to cook at high temperature for a long time. Protein in milk will change from sol state to gel state under the action of high temperature, which will lead to precipitation and reduce its nutritional value.

It can be seen that milk is really nutritious, and it is a convenient, affordable, economical and nutritious food, which is worth popularizing. Unexpectedly, ordinary milk also has so much knowledge! Actually, it's not just milk. Everything in the world contains a lot of knowledge, waiting for us to discover and explore!