Why does milk have a crust when heated?

This "skin" is caused by the fat and protein in the milk. Milk contains a variety of nutrients that dissolve or are evenly dispersed in water at room temperature to form a stable system. However, after the milk product is processed, there is an enzyme called lipase left in it.

During the storage of milk, these lipases break down the fat globulin (a type of protein) in the milk, releasing free fat globules. Since the density of fat globules is lower than that of water, the density of proteins is higher than that of waterAs a result, this breakdown causes the fat globules to float, and the remaining fat globule membrane proteins on the balls to float as well.

Once the milk is heated, the situation is different. When a liquid flows, friction occurs between its molecules, and the macroscopic manifestation of this friction is the viscosity of the liquid, and its strength can be characterized by the magnitude of the viscosity coefficient. When the temperature of the liquid increases, the molecular motion of the liquid intensifies, and its viscosity coefficient decreases accordingly.

Therefore, after heating the milk, the above-mentioned decomposition reaction accelerates, the viscosity coefficient of the milk also decreases, and at the same time, the upward resistance of the fat globules is also reduced, which leads to the rapid accumulation of some fat globules in the milk and the remaining proteins on the balls.

Due to the temperature difference between the surface of hot milk and the air, the moisture of the milk skin on the surface will evaporate quickly, and fat, protein and other substances will be exposed to the air, a coagulation is formed, which is the layer of milk skin.

It is mainly composed of fat and protein, and the protein is mainly lactalbumin, which shows that its nutritional value is still very high.

In order to prevent the formation of "milk skin", the only way to prevent the formation of "milk skin" is to constantly stir and constantly change the surface state during the heating process.

"Milk skin", just a little water evaporation, not to talk about the problem of nutrient loss. However, it is necessary to pay attention to the temperature and time of heating, too strong will cause nutrient loss.

That's the fat that converts into that layer of skin. So it's milk paper or grease.

Because when the milk is heated, certain substances in the milk will evaporate and remain on the surface.

Milk is a very popular beverage because it is rich in nutrients.

This is because some substances in milk react with heat, so they will peel.

Milk is rich in fat, protein, lactose and other nutrients. When the milk is boiled, the viscosity decreases, and nutrients such as fat will partially float, and in the process of evaporation and cooling, these floating nutrients form a film on the surface, commonly known as milk skin.

Because when milk is heated, its nutrients change qualitatively.

Because there will be something in raw milk that changes when it is heated.

This is because their material is very special, so this phenomenon happens.

This layer is basically made up of proteins, and when heated, the structure changes.

Because some of the things on the surface of the milk are digested, it will peel.

Summary. In fact, the skin on the surface of hot milk is coagulated protein. Milk is rich in fat, protein, lactose and other nutrients, some of which are dissolved in water and some are dispersed in water to form a stable system.

When the milk is heated above 40 degrees, due to the continuous evaporation of water from the liquid surface, the protein in the air and milk liquid surface is affected by the concentration and gells into milk skin, the main components are more than 70% milk fat and 20-25% protein.

Why do some milk have a layer on top of the skin when heated, and some have no or very little milk?

In fact, the skin on the surface of hot milk is coagulated protein. Milk is rich in fat, protein, lactose and other nutrients, some of which are dissolved in water and some are dispersed in water to form a stable system. When the milk is heated above 40 degrees, due to the continuous evaporation of water from the liquid surface, the protein in the air and milk liquid surface is affected by the concentration and gells into milk skin, the main components are more than 70% milk fat and 20-25% protein.

When the milk is boiled, the viscosity decreases, and in the static cooling process, nutrients such as fat will partially float up, and in the process of evaporation and cooling, these floating nutrients form a film on the surface, commonly known as milk skin. "Milk skin" is mainly formed by the floating of fat, but it is not only made up of fat. During the heating process of milk, the milk fat expands and the viscosity of the emulsion decreases, and these reactions promote the rise of the fat, causing the fat to accumulate on the surface of the milk.

As the heating continues, the fat globulin proteins are denatured, resulting in unstable fats that can easily coagulate together.

At the same time, these coagulated milk fats will also adsorb casein and whey protein in milk, reduce the tension on the surface of milk, and finally form a more stable film, which is what we see as "milk skin". Therefore, in terms of composition, there is fat in the "milk skin", and there are also some proteins adsorbed, which can be eaten, but it is not much nutritious.

The Mengniu pure milk I bought did not have a layer after heating, so does that prove that I bought a fake?

According to the staff of the "Mengniu" manufacturer, there are ways to identify real and fake "Mengniu" dairy products. The second is that the code is printed below the production date of the outer packaging of dairy products, and the shelf life date is printed on counterfeit dairy products. The third is that the production date of the "Mengniu" pure milk plastic packaging bag should be printed with embossing.

I didn't see a seal on what I bought.

I bought it on Tmall.

Tmall also has fakes.

That's a fake.

Yes dear. All right.

Milk is rich in nutrients such as fat, protein, lactose.

After the milk is boiled, the viscosity decreases, and in the process of static cooling, it will rise partially, such as fat and other nutrients in the process of evaporation and cooling, these floating nutrients form a film on the surface of milk, commonly known as milk. In fact, this layer is what we often hear about milk matching, the main components of milk are fat and protein, you can eat more, but the nutrition is not high.

With the improvement of people's living standards, many people now like to buy fresh milk, the nutritional value of fresh milk is very high, and there are no additives, but buy fresh milk to boil before drinking, when we go home when we boil the milk will find a layer of film floating on the surface of the milk, what kind of film is this? Is it OK to eat? It turns out that milk contains high-quality protein and calcium, which can only be killed by bacteria after boiling.

Floating ** is a coagulated protein, also known as milk**. Protein coagulation when heated, hard-boiled eggs coagulate because the protein in the egg coagulates, and the protein in milk coagulates because of the heating and becomes more nutritious.

Therefore, this membrane is milk skin, which can be eaten, but it should be noted that if the color of the milk is visibly grayish-yellow, do not consume it, which indicates that there are too many artificial additives in the gel and milk, which causes the milk to change color, and consumption is harmful to the body. For people who don't sleep well, it is recommended to drink a bag of milk every day before going to bed, which is good for promoting sleep, but do not drink milk on an empty stomach.

When milk is heated, a layer of epidermis forms on the surface, a phenomenon that is not only present in milk but also in soy milk. So why is there this layer of milk? This layer** is heating soy milk.

In the process of milk, the surface water evaporates, and the resistance of the fat globules to rise is correspondingly reduced, resulting in the rapid accumulation of some fat globules and remaining proteins on the surface of the milk. In other words, milk husks are actually moisture caused by the temperature difference between liquid proteins, fats, and sugars on the surface and the air, and after rapid evaporation, substances such as fats, proteins, etc., are exposed to the air to form a solidified substance.

When the milk is warmed, a layer of skin appears on top of it and can be eaten, which is caused by the fat and protein in the milk rising.

Milk contains a variety of nutrients that provide the following benefits: Protein supplementation: Milk is rich in a variety of amino acids, providing the body with a large amount of high-quality protein.

Some components in milk can inhibit cholesterol production, and regular milk consumption can lower blood pressure and reduce the risk of heart disease and stroke. Milk also has the effect of whitening and enhancing immunity. Calcium supplement Zen sells:

Milk contains a variety of mineral elements, which are easily absorbed by the human body, and drinking more milk can supplement calcium for the human body, enhance bone mass and prevent osteoporosis. The iodine, zinc and lecithin in milk can greatly improve the work efficiency of the brain and enhance the fatigue resistance of the heart and nerves. Vitamin supplements:

Milk is rich in vitamin D, vitamin B and other vitamins, which are conducive to the health of the human body.

It should be noted that drinking milk on an empty stomach will dilute gastric acid, affect digestion and absorption, and easily lead to abdominal pain and diarrhea, so it is not advisable to drink milk on an empty stomach.

This is because when the milk is heated, the temperature inside the milk is completely different from the temperature in the air, so a layer of cream will be formed.

Because during the heating process, the protein is denatured, so that the fat accumulates, so this layer of skin is produced.

The membrane on top of the hot milk is the milk skin

It is a thin skin formed on the surface of fresh milk after boiling and cooling, which is white or yellowish. The outer sides of the milk skin are made up of proteins, and the inner side is a thick layer of fat. The outer protein layer protects the inner fat from oxidation or delays oxidation.

Among them, 10%-20% protein, 40%-50% fat, less than 10% water, and the rest are carbohydrates and minerals.

Milk skin

The preparation method of milk skin is to put the fresh milk into the pot and cook, control the fire, bake over a slight fire, and stir constantly, so that the water slowly evaporates, the milk is concentrated, and it is condensed into a round yellow milk cake at the bottom of the pot, and it is dried in a cool place. The milk skin is pure yellow and white, with oil stains and dots, honeycomb sand holes are all over, the entrance is creamy and fragrant, crispy and soft, not greasy, and rich in nutrition.

It can not only be used for daily consumption, but also is the best quality for New Year's festivals, welcoming relatives and marrying women, and it is also a gift for visiting relatives and friends and condolences to elderly patients. The elderly like to cut the milk skin into small pieces and soak them in milk tea to eat. If it is cut and served on a plate, it is a great creamy snack as a dried fruit gummies.

1. Add an appropriate amount of water to the flour, starch and baking powder (two teaspoons) and stir well, add a little salad oil, and stir into a crispy paste; 2. Cut the prepared milk skin into diamond-shaped pieces; 3. Add salad oil to the pot on the heat, wait for the oil temperature to rise to 4 to 5 hot, hang the crispy paste on the milk skin and fry it to set, remove and drain the oil, and when the oil temperature rises to 5 to 6 percent, then put it in and fry it until golden brown and set aside.