If there is a small amount of yolk in the egg white, it is difficult to make it. Long-term use of electric egg beater can still be done, but it cannot be done manually. Because egg yolk contains lecithin and oil, both of them can play the role of defoaming, which will affect the passing of time. If there is only a little, the high-speed transit time may be foamed for a long time. If the yolk drips too much, you can't send it away.

The composition of protein is composed of 90% water and 10% protein, and a little protein is the key factor. Protein is curly. After stirring hard, it will spread out and intertwine with each other. At the same time, stirring will make the liquid form many tiny bubbles, and the protein chain will form a stable net outside the bubbles, and then it will become more and more robust. The bubbles formed by stirring will be wrapped by protein net to form protein foam.

In the process of making cakes, it is often required that the protein must not have egg yolk, and the basin and beater should be water-free and oil-free, because egg yolk and oil will directly combine with protein molecules, thus interfering with the formation of protein chains, and it is difficult to form a protein net outside bubbles, so it is necessary to separate the protein from the egg yolk to avoid sending it away.