Studies On Tofu-gel

Tofu has been the most important traditional soybean food in China. It is of very high quality nutritionally and has physiological functions. As domestic economy is developing steadily, familial workshop will necessarily be replaced by large-scale factory for tofu production. Since the skills and experience of handicraftsman could not resolve the technical problems emerging in tofu manufacture by machine, scientific research on tofu processing is necessary. Different tofu-making procedures are compared and analyzed. The simple and manipulable measuring methods of tofu quality are established. Adding coagulant into soymilk at low temperature, the effect of some factors on tofu-gel strength, water-holding capacity and microstructure are studied. These factors include soybean variety, soybean protein composition and concentration, coagulant type and concentration, and processing conditions. The contribution of different chemical forces to tofu-gel network are investigated. The two-step heating method is invented to modif soybean protein gelation property. Tofu is a gel product with a three-dimensional network structure. The network is formed by soybean protein coagulation by coagulant. Although the procedure of tofu-making varies with different kinds of tofu, the mixing of coagulant with soymilk is a common operation. This operation has large effect on the yield and texture of tofu. When coagulant is mixed with soymilk at low temperature, the operation conditions can be controlled easily and the resultant tofu-gel has uniform texture. Tofu-gel sength and water-holding capacity are not only important properties of tofu product but also reflecting coagulation condition of soybean protein. As semifinished product, tofu-gel strength and water-holding capacity influence texture reforming operation and finally has effect on yield and texture of tofu products. Different coagulants have different characters. With the increase of salt coagulant concentration, tofu-gel strength increased, and the protein molecular network become coarse and tofu-gel water-holding capacity decreased. The balance of attractive and repulsive forces between soybean protein molecular will be broke and coagulum syneresis will occur at a coagulant concentration that is called critical concentration for salt coagulant. The higher critical concentration is, the wider practicable salt coagulant concentration range is. Different salt coagulant has different critical concentration. The popular salt critical concentrations are as followed: CaCI2