Doubanjiang, also called broad bean paste, is a sauce condiment brewed from broad beans as the main raw material. It was originally produced in Sichuan. Silkworms are also called gourd beans. The broad beans used to make bean paste must be peeled off in advance to make them into petals.

Husking method 1. Wet shelling: After removing impurities from the broad beans, soak them in clean water to gradually absorb water until the beans have no wrinkled skin, no white core in the cross-section, and are in a germination state. After soaking, peel off the skin manually or mechanically. Chemical methods can also be used, that is, heating 2% sodium hydroxide solution to 80-85°C, and then soaking the broad beans soaked in cold water for 4-5 minutes. Take it out when the skin turns brown-red, and immediately rinse it with water until it is no longer alkaline. At this time, the skin is easy to remove, and the operation must be done quickly to avoid discoloration of the soybean meat. The characteristic of wet shelling is that the petals are relatively complete, but care must be taken to control the peeling and soaking time and not to be too long, otherwise the watercress will become stiff and difficult to soften after koji making and fermentation, which will affect the quality of the finished product.