Why gypsum is used to make bean curd

Tofu is made with gypsum, which is mainly composed of calcium sulfate, with small amounts of silicic acid and aluminum hydroxide. The water content of bean curd solidified with gypsum is about 90%, and the texture is fine and tender.

Brine and gypsum are electrolytes, the so-called point tofu, is to add enough electrolyte in the protein colloid, with electrolyte positively charged calcium and magnesium ions neutralize the negative charge of the protein colloid particles. Because there is no electrostatic repulsion between protein molecules, the dispersed protein colloids will be aggregated and settled down to become bean curd. This process is called colloid polymerization and sedimentation, this change process does not occur in the chemical reaction, belong to the physical process.

Extended information:

Nanfan tofu uses gypsum as a coagulant, and is therefore also called "gypsum tofu". Gypsum is chemically composed of calcium sulfate, which has low solubility and coagulates more slowly than brine. In the south, the solidified product is called "douhua" or "bean curd flower," and when it is put into a grinder or wrapped in a cloth, some water will ooze out and the hardness will increase.

The final tofu is generally higher in water content than marinated tofu and has a more delicate texture. Data show that 100 grams of southern tofu contains 6.2 grams of protein, 2.5 grams of fat, carbohydrates are 2.4 grams, while calcium and magnesium are 116 milligrams and 36 milligrams, respectively.

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