Extraction of gelatin from bigeye snapper (Priacanthus tayenus) skin for gelatin hydrolysate production

Bigeye snapper skin was pretreated with 0.025 N NaOH for 2 h and 0.02 M acetic acid for 2 h. Minced pretreated fish skin extracted at 80, 90, 100oC for 1, 2, 3 h and 110, 120, 130oC for 30 min were compared. The result showed that protein content and hydroxyproline (Hyp) yield of skin gelatin increased with increasing extraction temperature and time (p<0.05). The samples extracted at 120 or 130oC for 30 min and 100oC for 3 h showed the highest Hyp yield (76.36, 68.44 and 68.24%, respectively). Peptide bonds hydrolyzed, expressed as degree of hydrolysis, of samples ranged from 3.54 to 4.92%. SDS-PAGE pattern of gelatin indicated that hydrolysis of gelatin occurred during extraction at 100 to 130oC. The degradation of the fish gelatin resulted in the low bloom strength of gelatin gel. Bloom strength and L*, a*, b* values of gelatin gel (6.67%, pH 7) extracted at 120oC, 30 min were 62.6 g and 32.58, -1.67, 6.14, respectively. The solubility of gelatin was greater than 85% at all pH treated (1-10).