Rheological properties of MgCl2-coagulated tofu and conditions for hard tofu production in China
2004
Cheng, Y. (Tsukuba Univ., Ibaraki (Japan)) | Shimizu, N. | Kimura, T.
Abstract This study investigates the rheological properties and microstructure of MgCl2-coagulated tofu (Mg-tofu) to obtain useful information for hard tofu production in China. The rheological properties of Mg-tofu are affected by soymilk concentrations and coagulant concentrations. A low MgCl2 concentration (15 mM) resulted in soft tofu gel ; increasing the MgCl2 content produced a hard tofu. Increasing the protein content of soymilk also commonly increases the rupture stress of tofu. However, an excessively high concentration of MgCl2 caused a ductile rupture of tofu at low protein concentration. MgCl2 exhibited a relatively narrow optimal range for coagulation of tofu. The stress relaxation curve of Mg-tofu, similar to that of CaSO4 and glucono-delta-1actone (GDL), can be fitted with a four-element Maxwell model that includes two Maxwell models. The parameters obtained from the four-element Maxwell model, in particular the viscous parameters and stress relaxation times, increased with an increase of the protein content in soymilk. It is possible to produce Mg-tofu that has a similar rupture stress to that of commercial tofu in China. The narrow optimal range and its rapid reaction with soy protein may cause difficulties in handling during industrial hard tofu production using MgCl2 ; this might be improved by mixing it with GDL or CaSO4.
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