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Dynamic viscoelasticity measurements and compression tests of soybean proteins after the addition of glucono-δ-lactone (GDL) or calcium sulfate were carried out to analyze the gelation process of tofu (soybean curd). The gelation curve, viscoelasticity as a function of time, was analyzed and found to fit first-order reaction kinetics. The difference between GDL-induced and calcium-induced gelation was mainly in the kinetics ; i.e., gelation by calcium was faster. The structure of calcium gels inferred from the rheological properties was quite similar to that of GDL gels. It is suggested that the gelation of tofu is a two-step process : (1) protein denaturation by heat and (2) hydrophobic coagulation promoted by protons from GDL or by calcium ions. The addition of GDL or calcium induces gelation by promoting aggregation via hydrophobic interactions. Charge-charge interactions may also be subordinately involved, while formation of disulfide bonds was not involved in the second process.

Dynamic viscoelastic study and compression testing on gelation of soybean 7S and 11S proteins by glucono-6-lactone (GDL) were done to elucidate the gelation process of tofu (soybean curd). Gelation curves at constant temperatures observed in dynamic viscoelastic measurement were approximated by first-order reaction kinetics. Both storage and loss moduli at the final stage of the gelation for 7S-GDL gels showed almost the same value as those of 11S gels when concentrations of protein and GDL were the same

7S globulin was isolated according to a new method from soybeans. Its physicochemical properties were studied by differential scanning calorimetry (DSC) and by dynamic viscoelastic measurements. Heating DSC curves for 7S globulin showed only one endothermic peak. Extrapolation of the incipient temperature (T i ) and the endothermic peak temperature (T p ) observed at slow heating rates in DSC curves to 0 o C/min led to the result T i0 =64 o C and T p0 =70 o C

Dynamic viscoelasticity studies on gelation of soybean 11S protein by glucono-δ-lactone have been done to analyze the gelation process of tofu. Observed gelation curves at constant temperatures were well approximated by first-order reaction kinetics. The saturated storage modulus depended mainly on the concentration of 11S protein. The saturated modulus was proportional to 3.4 th power of 11S concentrations. The rate constant of the gelation increased with increasing gelling temperature and was mainly governed by the concentration of glucono-δ-lactone