Brine, scientifically called bittern, is the mother liquor left in the salt pond after salt is made from seawater or salt lake water. The main components are magnesium chloride, calcium sulfate, calcium chloride and sodium chloride, which are bitter and toxic. After evaporation and cooling, magnesium chloride crystals are precipitated, which are called halogen blocks. It is a commonly used coagulant for making tofu in northern China, which can make protein in soybean milk coagulate into gel and analyze the water. Tofu made of bittern as coagulant has strong hardness, elasticity and toughness, and is called old tofu, or north tofu and hard tofu. As the proverb goes: Bitter water points to tofu, everything has its vanquisher. When using bittern as coagulant to make tofu, the concentration is generally18 ~ 22 be', and the dosage is about 2% ~ 3.5% of the weight of raw soybean. In addition to brine, tofu in the south is generally made of gypsum. At present, a kind of tofu called glucono delta-lactone is also commonly used, and the tofu that comes out of the pad is called lactone tofu.

tofu curd

Tofu brain, a famous traditional snack of Han nationality, is often mixed with tofu flower and bean curd. According to different tastes in different places, the north prefers salty food, while the south prefers sweet taste, and some areas like Sichuan like hot and sour taste.

Tofu brain and tofu pudding are both intermediate products of tofu, and there is not much difference in composition. Tofu brain is the first to come out, it is tender and soft, and it is difficult to pick it up with chopsticks. It needs to be filled with a spoon. When the bean curd is solidified a little, it is bean curd. Compared with bean curd, it tastes slippery and can be picked up with chopsticks to eat. Tofu is made from tofu after it is compacted and solidified in a mold.

Bean curd is made by soaking soybeans for about 4-8 hours according to the variety or personal preference. After the soybeans are saturated with water, they are beaten, filtered and boiled, and then cooled to 90℃. Finally, add the coagulant and let it stand for 5 to 15 minutes.

Tofu brain is a highly nutritious food made of soybean protein. Similar to old tofu (old tofu is slightly harder than tofu brain, but the shape is the same. Tofu brain is like a young girl, while old tofu is like a semi-old beauty. Tofu brain is mostly sold in the morning, and old tofu is in the afternoon. Tofu brain is marinated, and old tofu is accompanied by soy sauce and other vegetarian dishes. )

Tofu brain is a semi-finished product in the process of making tofu. Cooked and hot soybean milk reacts with coagulant, and soybean protein sol (that is, soybean milk) is protein agglomerated. If the ratio of reactants is appropriate and the reaction conditions (temperature, concentration, stirring degree, etc.) are appropriate, soybean protein will completely solidify to form tofu brain. It is one of the four treasures of Ganzhou (now Ganxian).

coagulator

Commonly used coagulants are

① Metal ions: bittern such as brine (magnesium chloride solution) and gypsum.

② Acids: gluconic acid δ lactone (decomposed into gluconic acid by heating), vinegar, acid slurry water, etc. Because it is difficult for brine to solidify completely, and it is inedible, the bean curd we often eat is made from edible gypsum or lactone.