Autolysis study of bigeye snapper (Priacanthus macracanthus) skin and its effect on gelatin

Autolysis of bigeye snapper (Priacanthus macracanthus) skin was studied. The maximal autolytic activity was observed at 60 °C and pH 7.5. The proteolytic activity was strongly inhibited by 0.001 mM soybean trypsin inhibitor (SBTI), whereas pepstatin A (1 μM), EDTA (20 mM), EGTA (10 mM), iodoacetic acid (1 mM), PMSF (1 mM), E-64 (10 μM) and 1,10-phenanthroline (1 mM) showed no inhibitory effect. The result suggests that the major proteinase in bigeye snapper skin was a serine proteinase. Gelatin was extracted from bigeye snapper skin in water without and with 0.001 mM SBTI using a skin/water ratio of 1:7 at different temperatures (35, 40, 45, 50, 55 and 60 °C) for 12 h. In the presence of SBTI, the degradation was markedly inhibited. However, β-chain disappeared and α-chains underwent degradation to some extent at temperatures above 50 °C. Generally, a higher yield of gelatin was obtained as the extracting temperature increased (P<0.05). Nevertheless, the addition of 0.001 mM SBTI caused a lower gelatin yield. Therefore, heat-activated serine proteinase, most likely collagenase, involved in the degradation of collagen molecule and affected the yield and proteinaceous components in the resulting gelatin from bigeye snapper skin.