Improvement of gelatin extraction from bigeye snapper skin using pepsin-aided process in combination with protease inhibitor

Abstract

Gelatin extraction from bigeye snapper ( Priacanthus tayenus) skin was developed using a pepsin-aided process in combination with a protease inhibitor. The extraction efficiency was augmented by an acid-swelling process in the presence of bigeye snapper pepsin (BSP) at a level of 15 units/g alkaline treated skin at 4 °C for 48 h followed by extraction at 45 °C for 12 h with a yield of 40.3%. The complete degradation of β, α1 and α2-chains was observed in the resulting gelatin. To inhibit the proteolysis of BSP treated skin, heat treatments at different temperatures (70–90 °C) were used. The results indicated that the degradation still occurred in the resulting gelatin. When protease inhibitors were added during the gelatin extraction, the degradation of the gelatin components was markedly prevented when soybean trypsin inhibitor (SBTI) at a concentration of 0.1 μM was incorporated. However, pepstatin A could not retard the degradation, suggesting that the pepsin used was not involved in the degradation. Hydroxyproline content and bloom strength of gels from gelatin extracted from bigeye snapper skin treated with BSP and with porcine pepsin were similar, but their bloom strength was greater than the gelatin extracted from bigeye snapper skin by the conventional process, which had a substantial degradation of gelatin components. However, gelatin from bovine bone exhibited a greater bloom strength than did bigeye snapper skin gelatins, possibly due to higher hydroxyproline content.