RHEOLOGICAL CHARACTERISTICS AND GELATION MECHANISM OF TOFU (SOYBEAN CURD)

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