Bittern is an aqueous solution of crystallized magnesium chloride, which belongs to electrolyte solution. It can neutralize the charge of ions adsorbed on the surface of colloidal particles, and make protein molecules condense to obtain tofu.
Since tofu is used to coagulate protein, the gel used is not necessarily bittern. Other products, such as gypsum, ester acid and citric acid, have the same effect, and tofu can be used.
The origin of tofu
The origin of tofu can be traced back to the Han Dynasty. During the Han Dynasty, Huai
Farmers in the river basin have used stone water mills. Farmers soak rice and beans in water, put them in a water mill with a funnel, grind them into paste and spread them in a pot to make pancakes.
Pancakes and homemade soybean milk are the daily food of farmers in two rocks of Huaihe River. Farmers have accumulated various experiences in planting, boiling, grinding and eating beans. Inspired by the phenomenon that soybean milk has deteriorated and coagulated for a long time, people finally created the earliest tofu by the original self-sedimentation method.
According to legend, Liu An, the king of Huainan in Han Dynasty, started tofu. Liu An is the grandson of Emperor Gaozu Liu Bang, and his fief is in Huainan. He once recruited a large number of alchemists, pharmacists and immortals. They know the chemical knowledge, and improved the method of making tofu by farmer anonymous. Gypsum or bittern was used as coagulant, and white and tender tofu was made. It's possible. Tofu, in the Five Dynasties, appeared in the north and south food markets.