Textural and Rheological Properties of Soy Protein Isolate Tofu-Type Emulsion Gels: Influence of Soybean Variety and Coagulant Type

The contribution of soybean variety and coagulant type to the textural and rheological properties of soy protein isolate (SPI) tofu-type emulsion gels was studied. SPIs from eight soybean varieties were subjected to amino acid and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, and results showed that the 11S fraction proteins (r = 0.833, p < 0.05) and the ratio of 11S to 7S (r = 0.920, p < 0.01) were positively correlated with the hardness of CaSO4-induced emulsion gels and glucono-delta-lactone (GDL)-induced gels, with the correlation coefficients of 0.827 (p < 0.05) and 0.893 (p < 0.01), respectively. In the case of microbial transglutaminase (MTGase), strong relations between the content of glutamate (r = 0.886, p < 0.01) and lysine (r = 0.810, p < 0.05) and gel hardness were found. Rheological data demonstrated that CaSO4-induced emulsion gel was stiffer with high rigidity but gel induced by MTGase performed better elasticity. The findings of this study are of great importance to further understand the gelation mechanisms of different coagulants and provide useful information for the development of SPI-based filled tofu.