The principle of soup white is that lecithin is at work. Lecithin contains lipophilic groups and hydrophilic groups. Generally speaking, it can carry a drop of water in the left hand and a drop of oil in the right hand. If it carries enough oil, the soup we see is white due to the refraction of light. This is called "emulsification".

Frying sheep bones in oil and then flushing them is an "emulsification" exercise;

When the soup is cooked with strong fire, the oil on the surface is rolled into the soup, and lecithin can be carried to the oil. This is also an "emulsification" movement. The so-called big fire boiled white and small fire boiled clear.

But be careful not to always have a big fire. Cooking soup should take a long time with a small fire, otherwise the white is white and the soup is not fresh. Note: The principle of soup freshness is that protein is converted into amino acids (the main component of monosodium glutamate is amino acids). During the fire, protein quickly solidified and amino acids could not be fully converted, so the soup is not fresh. This is why braised pork needs a small fire and stew slowly to be delicious; Stir-fried pork slices certainly don't taste like braised pork. That's why.

Animal raw materials such as mutton, fish and shrimp are rich in lecithin. In addition, soybean oil and pig oil also contain a lot of oils and fats, so it is effective to use them to make white soup when frying.