Antioxidative activity and properties of fish skin gelatin films incorporated with BHT and α-tocopherol

Antioxidative activity and properties of bigeye snapper and brownstripe red snapper skin gelatin-based films incorporated with BHT (butylated-hydroxy-toluene) or α-tocopherol were investigated. Changes in FTIR spectra of fish skin gelatin films were observed when BHT or α-tocopherol at a level of 200 ppm was incorporated, suggesting some interaction occurred between gelatin molecules and the antioxidants added. Incorporation of BHT generally increased tensile strength (TS) and elongation at break (EAB) of film from bigeye snapper skin gelatin, but decreased EAB of film from brownstripe red snapper skin gelatin (P<0.05). Addition of α-tocopherol (200 ppm) decreased TS and EAB of film from brownstripe red snapper skin gelatin, and lowered EAB of film from bigeye snapper skin gelatin (P<0.05). Both BHT and α-tocopherol decreased water vapor permeability (WVP) of resulting film from skin gelatin of both species (P<0.05) but affected the transparency differently, depending upon gelatin source. During storage, all films had an increase in TS with a coincidental decrease in EAB (P<0.05). Antioxidative activity of fish skin gelatin films incorporated with BHT or α-tocopherol increased markedly with increasing storage time as indicated by the increase in DPPH radical scavenging activity (P<0.05). Films without and with BHT or α-tocopherol incorporated showed a preventive effect on lard oxidation as evidenced by the retardation of thiobarbituric acid reactive substances (TBARS) and peroxide formation.