Change in quality of preheated gel and two-step heated gel from walleye pollack [Theragra chaleogramma] and chum salmon on addition of microbial transglutainase [Oncorhynchus keta]

Frozen surimis of walleye pollack and chum salmon were ground with 3% NaCl and 0.3% food additive containing microbial transglutaminase (TGase). The salt-ground meats were heated at 25°C or 40°C for various periods to prepare preheated gel and subsequently heated at 90°C for 30 min to obtain two-step heated (kamaboko) gel. Quality of the gels was evaluated from the changes in gel properties (breaking strength and breaking strain) as a function of preheating time. Subunit composition of myofibrillar proteins in the gels was also analyzed by SDS-PAGE and densitometry. Results were as follows: 1) Gel formation of the salt-ground meat from both frozen surimis was largely enhanced by the addition of TGase. 2) The characteristic gel forming profile of each salt-ground meat induced by heating at 25, 40°C, and subsequent heating at 90°C, changed nearly the same as with TGase. 3) The cross-linking reaction of myosin heavy chains markedly proceeded in the preheating gels by the addition of TGase. During the subsequent heating at 90°C, the cross-linking reaction did not proceed further. It is evident that the kamaboko gel forming nature of the salt-ground meats from walleye pollack and chum salmon frozen surimis was essentially altered by the addition of TGase. The possible non-covalent type forces between myofibrillar proteins contributing to gel formation in the presence and absence of TGase are discussed.