Fish meat is often accompanied by the dissolution of certain substances during heating. Dissolved substances usually include free water in meat, but also contain a small amount of sarcoplasmic substances such as fat, sarcoplasmic protein and elastin, which are dissolved by muscle fiber cells and melted by hot melting. Gelatin formed by collagen dissolves. The reason why the soup is milky white is that during cooking, the fat in the meat overflows, some water-soluble protein in the muscle tissue and lecithin in the bone dissolve, and collagen in the skin hydrolyzes into gelatin molecules.

Meanwhile, due to heating, the soup will continue to boil in the pot. Boiling will crush adipose tissue into fine particles. Lecithin, gelatin molecules and some protein with emulsifying properties will be used as emulsifiers. Particles are stably and evenly dispersed in water to form an oil-in-water emulsion, which makes the soup as white as milk. Therefore, the milky white fish soup is mainly due to the optical effect caused by the fat in the fish soup being wrapped by emulsifier or soluble protein and emulsified and suspended in water.

The whiter the fish soup, the higher the fat content. Therefore, "three highs" and pregnant women should not eat frequently. If the fish soup is milky white and black, it is likely that the fish itself has a high fat content or has been fried in oil before cooking the soup. It is difficult to avoid eating too much fat in milk fish soup. Therefore, people who are obese and suffer from hyperlipidemia, hypertension, hyperglycemia, hyperuricemia and gout need to avoid eating them frequently.

In fact, the concentration of fish soup has nothing to do with its nutritional value. Many people "don't drink soup" largely lead to nutrient loss. Due to cooking, the ingredients themselves are not completely dissolved in the soup. Usually what we call soup is actually the function of fat. But thick soup is lighter than light soup, so it is whiter.