The production process of tofu

1. Raw material processing. Take 5 kilograms of soybeans, peel them and sieve them, wash them and soak them in a water tank for 4 to 5 hours in winter and 2.5 to 3 hours in summer. The soaking time must be mastered and cannot be too long, otherwise the pulp will be lost and tofu will not be made.

2. Put 250 grams of raw gypsum (20-30 grams of gypsum per kilogram of soybeans) into the fire for roasting. This is a key process. The degree of roasting of the gypsum must be mastered (use a hammer to gently Crush the plaster until you see it has just burned through the core). If the gypsum is too raw, it is difficult to use; if it is too cooked, not only will it not make tofu, but the soy milk will smell like chicken feces.

3. Grind the beans and filter the pulp. After the soybeans are soaked, take them out and grind them into pulp at a ratio of 6 kilograms of water per kilogram of soybeans. Use a bag (made of sewn tofu cloth) to pack the ground slurry. Pinch the mouth of the bag tightly and squeeze out the soy milk. After squeezing the soy milk, you can open the bag, add 3 kilograms of water, mix well, and continue to squeeze the milk again. Generally, 10 kilograms of soybeans yield about 15 kilograms of residue and about 60 kilograms of soy milk. When squeezing, do not let tofu residue mix into the soy milk.

4. Boil the paste and make some paste. Pour the squeezed raw pulp into the pot and bring to a boil. Do not cover the pot and skim off the foam on the surface while cooking. The fire should be strong, but not too fierce to prevent the soy milk from overflowing after boiling. The soy milk can be cooked until the temperature reaches 90~110℃. Insufficient temperature or too long time will affect the quality of soy milk.

5. Grind the burned gypsum into powder, mix it into gypsum slurry with a bowl of water (about 0.5 kg), pour it into the soy milk just scooped out from the pot, and stir it gently with a spoon. , after a few minutes, the soy milk condenses into tofu curd.

6. Make tofu. Within about 15 minutes of the tofu curd condensing, use a spoon to gently scoop it into a wooden tray (or other container) that has been covered with cloth. When it is full, wrap the tofu pudding with a cloth, cover it with a plate, and press it for 10~ In 20 minutes, the tofu is ready.

The scientific principle of making tofu. The raw material of tofu, soybeans, is rich in protein, with a protein content of 36 to 40%. The soybeans are soaked in water, ground, removed and heated to obtain a protein colloid (a kind of solution between and mixtures between suspensions and emulsions). Ordering tofu is all about trying to coagulate the proteins and separate them from the water. The gelling agents used include: brine, gypsum, ester acid, citric acid, etc., all have the same effect and can be used to order tofu. The gelling agent is made into an aqueous solution, which is an electrolyte solution. It can neutralize the charges of ions adsorbed on the surface of the colloidal particles and aggregate the protein molecules to obtain tofu.