(2) soaking: the purpose of soaking is to make the soybean absorb water and expansion, which is conducive to soybean crushing to extract the protein.
Soaked soybean water absorption is 1: (1-1.2), that is, soybean weight gain to the original 2.0-2.2 times.
Soaked soybean surface smooth, no wrinkled skin, bean skin easily does not fall off, feel strong.
(3) grinding: after soaking soybeans, protein body membrane becomes brittle, but to make the protein soluble, must be appropriate mechanical crushing.
If you look at it from the point of view of protein solubilization, the more thoroughly the soybean is broken, the easier the protein is solubilized.
But the grinding is too fine, the cellulose in the soybean will enter the soybean milk with the protein, so that the product becomes rough, dark,
And also not conducive to the separation of slurry, so that the product yield is reduced. Therefore, the general control of grinding fineness of 100-120 mesh.
Actual production should be adjusted according to the tofu varieties of coarse degree of inlay, and control the residual protein in the dregs of less than 2.6% is appropriate.
Use stone mill, steel mill or sand plate mill for crushing. After grinding, the bean paste is separated by flat sieve and horizontal centrifugal sieve to fully extract the bean paste.
(4) Cooking: Cooking is the process of thermal denaturation of the proteins in the soybean milk by heating. On the one hand, to create the necessary conditions for the latter order of pulp,
On the other hand, to eliminate the anti-nutritional components in the soybean milk, sterilization, reduce the odor, improve the nutritional value, and prolong the freshness of the product.
Cooking method according to different production conditions, you can use the clay stove iron pot cooking method, open tank steam cooking method, closed overflow cooking method and other methods.
Cooking temperature should reach 100 ℃, time 5min or so.
(5) coagulation and molding: coagulation is the soybean protein in the heat denaturation based on the role of coagulant,
by the process of sol-gel state into a gel state. Production is accomplished through two processes: brain-spotting and brain-squatting.
Dotting the brain is the coagulant according to a certain proportion and method added to the cooked soybean milk, so that the soybean protein soluble into a gel, the formation of tofu brain.
Tofu brain is composed of soy protein in a mesh structure and water filled in it.
Generally speaking, the larger the mesh of the mesh structure of the tofu brain, the more firmly interwoven,
The better the water retention, made of soft and tender tofu, the higher the yield of the product;
On the contrary, the tofu made of stiffness, lack of toughness, the yield of the product is also low.
After the point of brain, the protein network structure is still not solid, only after a period of time to complete the solidification.
Based on the different varieties of tofu, squatting time is generally controlled in 10-30min.
Molding that is, the solidified tofu brain into a specific mold, applying a certain amount of pressure, squeezing out the excess of the yellow pulp water,
so that tofu brain is densely combined together into a certain amount of water content, and elasticity, toughness of the tofu,
Different products vary in the pressure applied. The pressure applied varies from product to product.