Why can milk have a layer of skin on its surface after heating
Sihai network: most people like to drink hot milk in winter. When the milk is heated and cooled, there will be a layer of skin on the surface. Many people do not know what it is. Some people say it is milk, the essence of milk. Some people say that impurities in milk can not be eaten. What is it? Let's look at you next.
During the heating of milk, the expansion of milk fat and the decrease of emulsion viscosity promote the floating of fat and the accumulation of fat on the surface of milk. With the continuous heating, the fat globule membrane protein denaturation, losing the fat film of the fat ball is unstable, and it is easy to coagulate together. At the same time, the milk fat that coagulates together will adsorb casein and whey protein in milk. Reduce the surface tension and finally form a more stable skin film, which is what we see as "milk skin" (note that boiling milk skin does not mean that there is no fat in the remaining milk).
Therefore, the milk skin is mainly composed of fat and a small amount of protein, while the so-called "nutrients are boiled out" is not reasonable.
There is nutrition in the milk skin, so you don't have to abandon it
Although the main component of milk skin is fat, from the perspective of nutrition, the fat and protein contained in milk skin are also essential nutrients for human body. When people drink milk, if they do not need to control the fat intake, they can eat the milk skin together.