It just contains more fat droplets.
People believe the milky white color of broth represents nutrition, but the truth is that the milky white color is simply an emulsification phenomenon where fat droplets are evenly distributed in water. When light encounters these tiny droplets, it scatters, creating a visually milky appearance. Milk is milky white for this exact same reason.
In fact, the fat in milk is pale yellow; you can see this from butter. However, after emulsification, it becomes milky white, such as in the case of light cream. The milky white color of fish soup, meat soup, duck frame soup, and pig's trotter soup is for the exact same reason. As long as you have three components, you can create "milk soup": fat droplets, an emulsifier, and water. In these soups, there are ingredients rich in fat. Under the action of boiling and churning, the fat forms droplets, which are then enveloped by an emulsifier, creating a stable emulsified system that is evenly dispersed in the water. So, where does the emulsifier come from? It comes from the soluble proteins in the ingredients. Proteins have certain emulsifying properties; they coat the outside of the fat droplets, allowing the fat, which is completely incompatible with water, to be evenly dispersed in it.
From this, you can understand that whether you can successfully make a milk soup has little to do with its nutritional value. However, making a milk soup does require some technique; that is, the operation must fully meet the various conditions for forming an emulsion.
Key Points for Making Milky White Soup
To successfully make a milk soup, you need to provide ingredients rich in fat and ingredients rich in soluble protein. For example, crucian carp is an ingredient rich in soluble protein but low in fat. If you only use crucian carp to make soup, you won't get the milk soup effect. How to supplement the fat? You need to pan-fry the fish in oil. When this fried oil is added to boiling water, it forms small fat droplets. However, these droplets are still too large, and without an emulsifier to help them, as soon as the water calms down, they will clump together and fail to form a milk soup.
Therefore, you need to simmer over medium heat to keep the soup constantly boiling, so that the small fat droplets are continuously broken up and cannot clump together. At the same time, during the simmering process, the soluble proteins from the fish gradually dissolve out, coating the outside of the fat droplets to form the milk soup. Once it becomes milky white, you can continue to simmer over low heat.
Therefore, the key points for making a milk soup are completely different from those for making a clear soup. A clear soup requires no added oil and no obvious boiling process. To make a milk soup, you must use ingredients rich in fat, or add cooking oil, and pay attention to maintaining a boil. You can only add boiling water, not cold water.
If you want to make a milk soup simply, you only need one simple ingredient: mayonnaise (pale yellow or milky white salad dressing). Egg yolks are rich in lecithin, which is an excellent natural emulsifier. Salad dressings and mayonnaise are products made using the emulsifying properties of egg yolks. By adding mayonnaise to boiling water and stirring, you can easily get a milky white soup.
To control your weight, you should drink milk soup less often.
From this, you can understand an important fact: milk soups are all soups that contain a considerable amount of fat. Therefore, for people who are not deficient in fat and protein, drinking milk soup may not be nourishing, but it will definitely lead to the intake of a lot of fat.
When drinking soup with floating oil on top, people are usually very vigilant and often skim the oil off before drinking. However, when drinking milk soup, people are often complacent, not realizing it contains a lot of fat. Because it tastes delicious, they think it is very nourishing and often drink several more bowls.
Therefore, it is necessary to remind people that if you want to control your weight, you should not make milk soup frequently, and you should also pay attention to the quantity when you do. Compared to this, drinking clear soup is a safer bet.