Is the tofu making process salting out or polysinking?

Hello, it's poly-sinking.

Soybeans, the raw material of tofu, are rich in protein, with a protein content of 36% to 40%, and protein is a polymer compound composed of amino acids, with free carboxyl and amino groups on the surface of protein. Soak the soybeans in water, swell and soften, grind them into soy milk, then filter out the okara and bring them to a boil. Due to the action of these groups on water, a colloidal substance with an aqueous film of the same charge is formed on the surface of the protein particles, so that the particles are isolated from each other and will not bond and sink due to collision, forming a "colloidal" solution (a mixture between the solution and the suspension and the emulsion).

In order to turn the colloidal solution into tofu, it is necessary to point the brine, that is, to try to make the protein coagulate and separate from the water. Point brine.

With salt brine or gypsum, salt brine mainly contains magnesium chloride, gypsum is calcium sulfate, which is an electrolyte solution, and will be divided into many charged in water.

The small particles, positive and negative ions, are deprived of the protein's water film by the hydration of these ions, so that there is none.

Enough water to dissolve the protein.

In addition, the positive and negative ions of the salt inhibit the repulsion caused by the charge on the surface of the protein, so that the solubility of the protein is reduced, and the particles condense into a precipitate with each other, that is, the scattered protein particles can quickly aggregate.

When it came together, it became a white tofu brain. Squeeze out the water again, and the tofu brain becomes tofu. Tofu and tofu brain are coagulation.

Polylegume protein.

Soy milk with brine Soy milk is colloidal, and brine contains salt and is polysinking.

The chemical principle of making tofu: The main ingredient of soy milk is protein. Due to the carboxyl group and ammonia group on the surface of the protein, a gelatinous substance with the same charge is formed on the surface of the protein particles, so that the particles repel each other and cannot be combined and sink.

After the brine, because there are many electrolytes in the brine, many positive and negative ions are formed in the water, which destroys the repulsion effect and makes the protein combine and precipitate to form tofu feng. Salting-out: 1

Salting out generally refers to the process of adding inorganic salts to the solution to reduce the solubility of a substance and precipitate. For example, the process of condensing protein by enriching (NH4)2SO4; In the esterification reaction of acetic acid, saturated sodium carbonate solution was added to reduce the solubility of ethyl acetate and make its stratification phenomenon more obvious.

2.After adding some inorganic salt solutions to some protein solutions, the protein can be condensed and precipitated from the solution, which is called salting out and can be restored. The addition of certain heavy metal salts to some protein solutions can make the protein coagulate and precipitate out of the solution, which is called denaturation, which changes its properties and cannot be recovered.

3.Animal fat or vegetable oil and sodium hydroxide are stirred and heated in a saponification pot in a certain proportion, and the high-grade fatty acid sodium, glycerol and water formed after the reaction form a mixture. Add salt particles to the pot, stir and let stand to separate the sodium of advanced fatty acids from glycerin and water, and float on the liquid surface.

This reaction is used to make soap) Simply put, the protein is precipitated by using a high concentration of neutral salt; The solubility (s) of the protein is different, and the concentration of salt used for precipitation is different.