Tofu coagulant can be divided into two types: salt type and acid type. At present, some composite coagulants have also been developed at home and abroad.

(1) Gypsum

The main component is calcium sulfate. The solubility of calcium sulfate is low, and its solidification progresses slowly, so it can form smooth and tender tofu with good water retention properties. When using gypsum as the coagulant, the temperature of the soy milk cannot be too high, otherwise the tofu will become hard. Generally, it is more appropriate to control the temperature of the soy milk at 85°C. Under normal circumstances, about 2.2 to 2.8 kilograms of coagulant gypsum powder is needed for every 100 kilograms of soybeans.

(2) Brine

Also known as salt brine, it is a by-product of seawater salt production. There are two types: solid and liquid. The liquid concentration is generally 25~27°Bé, and the solid is a halogen block containing about 46% magnesium chloride. Whether it is liquid or solid, it needs to be adjusted to a solution of 15~16°Bé when used. The approximate usage range is 2 to 5 kilograms of brine (based on solids) per 100 kilograms of soybeans.

(3) δ-gluconolactone (GDL)

GDL is a new type of acid coagulant. It is easily soluble in water and will slowly decompose into gluconic acid when dissolved in water. When lactone is added to cooked soy milk, when the temperature of the soy milk reaches 60°C, the soybean protein begins to solidify. At 80 to 90°C, the solidified protein gel has the best water-holding capacity, and the tofu made has high elasticity and a smooth and refreshing texture. The usage amount of lactone is generally between 0.25 and 0.35 (based on soy milk).

(4) Composite coagulant

The so-called composite coagulant is a coagulant that is artificially processed from two or more ingredients. Granular coagulants such as organic acids or salts with coating films have been developed. It mainly utilizes the acid to be heated at normal temperature, the coating agent melts, and the organic acid wrapped inside also plays a coagulating effect. Organic acids that can be used include: citric acid, isocitric acid, sorbic acid, fumaric acid, lactic acid, gluconic acid and their lactones and anhydrides. When using citric acid, the added amount is about 0.05 to 5.0 of soy milk (10 solids). There are also coagulants made by combining gluconolactone (about 40), calcium hydrogen phosphate, potassium tartrate, sodium hydrogen phosphate, fumaric acid, corn starch, etc.