Effect of trypsin inhibitor in adzuki bean (Vigna angularis) on proteolysis and gel properties of threadfin bream (Nemipterus bleekeri)

Trypsin inhibitor (TI) from adzuki bean seed was partially purified by heat-treatment at 90 °C for 10 min and it was used to study the impact on proteolysis and gelling properties of threadfin bream (Nemipterus bleekeri). TI showed the inhibitory activity against sarcoplasmic proteinases and autolysis of threadfin bream mince and washed mince in a concentration dependent manner. TI was effective in proteolysis prevention as shown by more retained myosin heavy chain (MHC) on SDS-PAGE. Effect of TI (0.5, 1, 2 and 3 g/100 g) on the properties of threadfin bream surimi was also investigated. Breaking force and deformation of kamaboko gel increased as added levels of TI increased (p < 0.05). This was associated with lower levels of protein degradation, as evidenced by the decreased in trichloroacetic acid-soluble peptide content (p < 0.05). However, whiteness slightly decreased (p < 0.05) with increasing TI levels. Therefore, TI at an appropriate level could be an alternative food-grade inhibitor to improve gel properties of surimi.