Optical and thermo-mechanical properties of composite films based on fish gelatin/rice flour fabricated by casting technique

Packaging films based on fish gelatin-rice flour (FG-RF) at different blend ratios (FG-RF ≈ 10:0, 8:2, 6:4, 5:5 and 0:10, w/w) using 30% (w/w) glycerol as plasticiser were prepared and characterised. FG-RF composite films exhibited lower tensile strength (TS) and elongation at break (EAB), compared to FG film (P < 0.05). Higher water vapour permeability (WVP), but lower water solubility (WS) was obtained for FG-RF composite films having the increased proportion of RF (P < 0.05). Light transmission in ultraviolet (UV) and visible regions (200-800 nm) was lowered in all FG-RF composite films, indicating excellent light barrier characteristics. Based on FTIR spectra, significant changes in molecular structure and lower intermolecular interactions between FG and RF molecules were found in FG-RF (8:2) composite film. Thermogravimetric analysis indicated that FG-RF (8:2) composite film had only 7.61% (w/w) heat-stable mass residues in the temperature range of 50-600 °C. DSC thermograms suggested that FG-RF (8:2) composite film consisting of amorphous/microcrystalline layers of partially miscible aggregated junction zones and the coexisting two different order phases of unbound domains. SEM micrographs elucidated that FG-RF (8:2) composite film was rougher than FG film, but no signs of phase separation between film components were observed, thereby confirming their potential use as packaging material.