Effect of squalene as a glycerol substitute on morphological and barrier properties of golden carp (Probarbus Jullieni) skin gelatin film

Gelatin films prepared by using glycerol (GLY) and squalene (SQ) at different ratios (10:0, 7:3, 5:5, 3:7 and 0:10; w/w) as plasticizer were characterized. Incorporation of SQ reduced the moisture content of the gelatin film (p < 0.05). Films plasticized with GLY/SQ at a ratio of 5:5 (w/w) had highest tensile strength (TS), which was 61.7% higher than that using GLY as plasticizer (GLY). Nevertheless, a continuous decrease in elongation at break (EAB) was attained with increasing SQ ratios (p < 0.05). SQ films had a reduction in water vapor permeability (WVP) and oxygen permeability (OP), compared to GLY film (p < 0.05). Additionally, SQ films had slightly lower lightness with less transparency. Based on microstructure, the cross-section of films plasticized with only SQ (without GLY) presented extremely course structure with large particle size, compared to those plasticized with GLY/SQ mixture or GLY alone. Based on FTIR and DSC spectra, SQ decreased gelatin-gelatin interactions associated with a disordered structure. In addition, SQ film demonstrated lower melting transition (T-max), and enthalpy (Delta H), but a slightly increased glass transition temperature (T-g). Thermal degradation behavior of films showed that GLY film possessed a higher number of gelatin-gelatin interaction than that incorporated with SQ. Thus, SQ could replace GLY up to 50% to render stronger films with improved WVP as well as the OP of gelatin films.