Gelation of threadfin bream surimi as affected by thermal denaturation, transglutaminase and proteinase(s) activities

Surface hydrophobicity, reactive and total sulfhydryl groups, circular dichroism, and storage modulus (G') revealed that unfolding of actomyosin began at 35°C, while aggregation took place at 45°C. Optimum temperature of crude transglutaminase (TGase) was found at 37 and 55°C and pH 7-7.5. TGase activity was reduced from 99 unit/g dry weight in mince to 47 unit/g dry weight after screw pressing. Gels incubated at 25°C for 4 h and 40°C for 3 h showed an increased force at failure. Degradation of myosin heavy chain (MHC) was evident when incubation time at 40°C was extended. Iodoacetic acid (IAA) was found to be the most effective TGase inhibitor. Autolytic degradation of threadfin bream was highest at 60°C. Salt had no effect on autolytic activity. Force at failure and deformation of surimi gels decreased as incubation time at 60°C was prolonged, corresponding to a decrease of MHC.