Effect of Longan Seed Extract and BHT on Physical and Chemical Properties of Gelatin Based Film

Gelatin films developed from fish skin incorporated with longan seeds extract (LS) or butylated hydroxytoluene (BHT) at different concentrations were prepared and characterized. The film thickness was in the range of 35 to 37 μm, and the transparency was 3.24 to 3.36 for the films with and without the addition of LS or BHT ( p < 0.05). Significant increases in redness ( a *) and yellowness ( b *) values were observed when the concentration of LS increased ( p < 0.05). Water vapour permeability (WVP) slightly decreased when the concentration of LS increased, while no significant change was observed between the control and the BHT films ( p > 0.05). Tensile strength (TS) and elongation at break (EAB) were in the range of 48 to 53 MPa and 16 to 19 %, respectively. The highest (65.7 J/g) and lowest (38.7 J/g) transition enthalpy was found in the control and LS 500 ppm films, respectively. Slight differences in protein pattern were observed under SDS-PAGE between treatments of the film. These differences were also observed in the FTIR spectrum. Films incorporated with LS or BHT showed the preventive effect on lipid oxidation of soybean oil during 30 days of storage. At the level of 500 ppm, LS provided the highest efficacy for lipid oxidation retardation as evidenced by lower peroxide value (PV), and thiobarbituric acid reactive substances (TBARS) values ( p > 0.05). The addition of LS or BHT had an impact on the film properties derived from fish skin gelatin, especially when high levels were added.