It is said that Koreans put cooked soybeans on saddles and grab them at any time. Cooked soybeans only ferment naturally by using the horse's body temperature to form easily absorbed high-protein food. It is recorded in the "Afforestation Economy" published by 1760 that washed soybeans will become sticky when placed in a warm place with zircon. The food that people used to call "national jam" belongs to the same category as today's "green jam". Different from soy sauce, green jam can be eaten after 2-3 days of ripening, and it is an effective soybean fermented food to absorb nutrients.