1. Pickled bean curd. After boiling the tofu base with water, add salt to marinate it, put it in a jar and add auxiliary ingredients, and ferment it into fermented bean curd. The characteristics of this processing method: the tofu base is directly put into the jar without fermentation (no pre-fermentation), post-fermentation is carried out, and it matures relying on the microorganisms brought in the auxiliary materials. Its disadvantages are insufficient protease, long fermentation time, low amino acid content, and poor color and aroma, such as 4 Tangchang fermented bean curd and Hunan Zili mold-free bean curd.

2. Mucor fermented bean curd. Mucor is cultured on tofu base, which is called pre-fermentation. The white mycelium grows all over the surface of the tofu base, forming a tough skin film, accumulating protease, and creating conditions for later fermentation in the pickling jar.

Mucor requires lower temperatures for growth, and its optimal growth temperature is about 16°C. Generally, Mucor bean curd can only be produced under low temperature conditions in winter. The traditional process uses Mucor mold in the air and inoculates it naturally, which requires about 10-15 days of cultivation (suitable for family workshop production). Pure Mucor can also be cultured, artificially inoculated, and cultured at 15-20°C for 2-3 days.

3. Rhizopus type fermented bean curd. Using high-temperature resistant Rhizopus, through pure bacterial culture and artificial inoculation, fermented bean curd can be produced in the high-temperature season of summer. However, the rhizopus hyphae are thin, light gray, and have low protease and peptidase activities. The shape, color, and luster of the fermented bean curd produced are The flavor and physical and chemical quality are not as good as Mucor bean curd.