Yeast can loosen products, improve the flavor of products, and increase nutrition. However, yeast does not have the effects of drugs. 1. Loosening and improving the flavor of products: (1) Yeast can produce a large amount of carbon dioxide after fermentation in the dough, and a large amount of carbon dioxide stays in the gluten network organization, which can make the food organization loose and porous, and increase the volume. (2) In the process of dough fermentation, after a series of biochemical reactions, it can produce a unique fermentation flavor. 2. Increase nutrition: the main component of yeast is protein, but also contains essential amino acids, including lysine, which is more lacking in cereals, and also contains a large number of vitamins, especially B vitamins and niacin, which can improve the nutritional value of fermented foods.