The principle of brine tofu is that the raw material of tofu is rich in protein and the content of protein is 36% ~ 40%. After soaking in water, grinding, deslagging and heating, protein colloid (mixture of solution, suspension and emulsion) is obtained. The purpose of ordering tofu is to solidify protein and separate it from water.

Brine is an aqueous solution of crystallized magnesium chloride, which belongs to electrolyte solution. It can neutralize the ionic charge adsorbed on the surface of colloidal particles, and make protein molecules condense to obtain tofu.

Because tofu is used to coagulate protein, the gel used is not necessarily brine. Other products, such as gypsum, ester acid and citric acid, also have the same effect, so can tofu. It is also worth mentioning that in recent years, there is a boxed tofu on the market. White and delicate, the quality is obviously higher than that of tofu made by traditional methods. It turns out that its coagulant uses a new chemical substance-gluconolactone, which is also an example of the application of new technology in food processing.

Simply put, brine tofu is tofu made of brine (magnesium chloride), and gypsum tofu is tofu made of calcium sulfate.

Bittern tofu tastes soft and tough, with beany smell, less water content, slightly yellowish white color and rough texture. Commonly known as "old tofu" and "north tofu", it is mainly used for frying, frying, brewing and stuffing.

Gypsum tofu is tender, smooth, rich in water and white in color, commonly known as "tender tofu" and "southern tofu", and is mainly used for mixing, stewing, baking and making soup and soup dishes.