Effect of phosphoric acid concentration on physicochemical properties of Abalistes stellaris skin gelatin

Due to halal and health issues, the fish by-product (waste) is one of the best sources to substitute land animal gelatin. Abalistes stellaris has a hard texture in skins and known as leather jacket fish species. Moreover, its skins obtained as wastes in smoked fish processing and have not been utilized. Therefore, this study aimed to analyze the physicochemical properties of gelatin extracted from A. stellaris skins at a different phosphoric acid concentration (0.2, 0.4, and 0.6 M). This study conducted by a completely randomized design (CRD) with three replications, followed by Duncan's post-hoc test. The different pre-treatment of phosphoric acid concentrations showed significant differences (P<0.05) on yield, pH, chemical composition (moisture, protein, fat, and ash), gel strength, gelling, and melting points of A. stellaris skins gelatin. Only the viscosity parameter and an ash content of gelatin did not show a significant effect (P>0.05). The yield of A. stellaris skins gelatin ranged from 9.48% to 10.87%. The protein, moisture, fat, and ash content of skins gelatin ranged 74.55-81.41, 8.62-12.40, 0.43-0.73, and 1,48-1,79 (dry weight basis), respectively. Also, the gel strength and viscosity of skins gelatin were in the range of 1.28 N to 2.45 N and 3.83 cP to 4.21 cP. The amino acid composition of A. stellaris skins gelatin was rich in glycine, proline, alanine, and glutamic acid.