Emulsion film based on fish skin gelatin and palm oil: Physical, structural and thermal properties

Physical, structural and thermal properties of emulsion film based on fish skin gelatin containing palm oil at different levels (25%, 50%, 75% and 100%, based on protein), were tested. Particle size distribution (d(32) and d(43)) of film-forming emulsion (FFE) at all oil levels was similar after preparation (0 h) (p > 0.05) and slightly increased with increasing storage time, especially at 12 h (p < 0.05). Films incorporated with palm oil had lower tensile strength (TS) and elastic modulus (EM) but higher elongation at break (EAB) as the amount of palm oil increased (p < 0.05). Decreased water vapor permeability (WVP) and moisture content (MC) were observed for films having the increasing amount of palm oil (p < 0.05). Emulsion gelatin films with higher levels of palm oil had lower L*-value, whiteness index (WI), light transmittance but higher b*- and Delta E*-values (p < 0.05). The addition of palm oil generally resulted in the increased hydrophobicity and the weaker protein-protein interaction in film network, leading to the lower thermal stability. This was indicated by lower glass-transition and degradation temperatures of the resulting films. Most of oil droplets were imbedded in the matrix of emulsion films, regardless of palm oil levels used. Therefore, the levels of palm oil directly had the impact on physical, molecular structure and thermal properties of resulting emulsion gelatin film. (C) 2015 Elsevier Ltd. All rights reserved.