Red tile fish Branchiostegus japonicus meat degrades easily. In market, the small- sized fish is traded at a low price. Additionally, the population of red tile fish in the sea around Japan has reduced. Therefore, for effective utilization of small-sized red tile fish, the effect of endogenous proteases on heat-induced gelation of red tile fish surimi was investigated in the research. Fish gels from red tile fish surimi were prepared at different temperatures between 30 – 90 oC. After heating, the samples were cooled in ice water and then mechanical properties and SDS-PAGE patterns were analyzed. Homogenates prepared from the surimi were mixed with protease inhibitor solutions. The mixtures were incubated in water bathes at 40 or 60 oC. After heating, peptide contents in the supernatant and autolytic protein patterns were determined by the Lowry method and SDS-PAGE respectively. The surimi didn’t form heat-induced gels at 30 - 80 oC and SDS–PAGE showed that proteolysis markedly occurred. Addition of 1, 10-phenanthroline, benzamidine or SBTI prevented proteolysis. These results suggest that red tile fish surimi had extremely low gel- forming ability due to endogenous metalloprotease and trypsin-like serine protease.

Keywords: Fish products, Gelation, Protease inhibitor, Surimi