Tofu Manufacturing Process
Step 1: Sorting Soybeans
The protein content of soybeans is a crucial indicator of their quality: the higher the protein content, the better the soybeans. Additionally, it’s essential to produce tofu from non-GMO soybeans. In comparison to genetically modified varieties, non-genetically modified soybeans yield a higher pulp extraction rate, imparting a richer flavor to the final product.
Step 2: Soaking Soybeans
Soaking serves the purpose of allowing soybeans to absorb water and expand, facilitating the extraction of protein during the grinding step. The soaking time ranges from 8 to 18 hours, depending on water temperature and ambient conditions. The water absorption rate is approximately 1:1, meaning 100g of soybeans absorbs about 100g of water.
Step 3: Grinding Soybeans
The soaked soybeans are ground mechanically to form a paste. The appropriate particle size after grinding is 125 to 149 microns, depending on the requirements of the intended product. This range of size provides us two benefits: 1) it ensures efficient and maximum protein extraction; 2) it prevents excessive fiber from entering the soy milk, which will be obtained in the next step (high fiber content can make the soy milk turbid, ultimately affecting the mouthfeel of the tofu).
Step 4: Filtration
The purpose of filtration is to obtain soy milk. Specifically, soy milk and soy pulp are separated from the soy paste obtained in the previous step. The soy milk will be used to produce tofu, and the soy pulp can either be discarded or utilized in the production of other soyfoods.
Step 5: Boiling Soy Milk
The soy milk is brought to 100°C and maintained at a boil for a few minutes. Boiling serves three purposes: 1) to prepare for the next step of coagulation ; 2) to eliminate any undesirable odor, sterilize, and extend the shelf life of the product; 3) to remove anti-nutritional components from the soy milk, enhancing its nutritional value.
Step 6: Coagulation
The coagulant is added to the boiled soy milk to solidify it into a solid state. Once the coagulant is added, the soy milk is allowed to rest for a specific duration to achieve a stable structure for forming tofu.
Step 7: Moulding
Douhua, the coagulated soy milk obtained from the previous step, is broken up and then placed into molds. The purpose of this step is twofold: first, to shape the tofu; second, to further press out the soy whey, allowing the dispersed protein gel to coagulate more effectively.
