The effects of enzymatically aided acid-swelling process on gelatin extracted from fish by-products.

The objective of this study was to investigate the effects of the enzymatic aided acid-swelling process on gelatin obtained from fish by-products. For this purpose, gelatin was extracted by an acidic swelling procedure in the presence of protease extracted from Rainbow trout pyloric caeca. The yield of gelatin extraction and the most important physicochemical characteristics of the fish gelatin samples were investigated and compared with those of commercial bovine gelatin (CBG). The yields of gelatin from Epinephelus coioides skin (ESG) either with or without crude protease from pyloric caeca (15 units/g alkaline treated) were 14.98% and 50.89%, respectively. The yields of gelatin from Cyprinus carpio scales (CSG) with crude protease from pyloric caeca (15 units/g) were 49.97%. The gel strength of the CSG (259.66 g) was significantly higher than that of CBG (228.30 g) and ESG (187.75 g). Similarly, the gelling and melting points, foaming capacity and stability, and the SDS-PAGE pattern of gelatins were compared. The electrophoretic pattern confirmed the results of gel strength which was due to the narrower alpha and beta bands in fish skin and commercial bovine gelatins than that of fish scales gelatin. The results of this research showed that the production of high-quality gelatin can be achieved by the enzymatically aided acid-swelling procedure from fish scales and skin.