Blend film based on fish gelatine/curdlan for packaging applications: spectral, microstructural and thermal characteristics

Abstract

A series of novel fish gelatine/curdlan (FG/CL) blend films at different ratios (FG/CL ≈ 10 : 0, 8 : 2, 6 : 4, 5 : 5 and 0 : 10%, w/w) were successfully fabricated at pH 12 via a casting approach, and their physico-mechanical, spectral, microstructural and thermal properties were investigated as a function of CL content. FG/CL blend films exhibited lower tensile strength (TS) but higher elongation at break (EAB) and water vapour permeability (WVP), compared to FG film (P < 0.05). Increased contact angle (θ) and moisture content (MC), but decreased water solubility (WS) were obtained for FG/CL blend films having the higher proportion of CL (P < 0.05). Furthermore, the addition of CL decreased a*-(redness) and transparency values (P < 0.05), but enhanced L*-(lightness), b*-(yellowness) and ΔE*-values (total colour difference) (P < 0.05) in FG/CL blend films. Light transmission in ultraviolet (UV) and visible regions (200–800 nm) was lowered in all FG/CL blend films, indicating excellent light barrier characteristics. Significant changes in molecular order and decreased intermolecular interactions in the matrix of FG/CL blend film were determined based on FTIR spectroscopy. TGA and DTG curves displayed that FG/CL (8 : 2) blend film had enhanced heat stability as evidenced by higher heat-stable mass residues (34.1%, w/w), compared to FG film (26.6%, w/w) in the temperature range of 50–600 °C. DSC thermogram suggested the solid-state morphology of FG/CL (8 : 2) blend film that consisted of amorphous/microcrystalline phase of partially miscible FG/CL aggregated junction zones and the coexisting of unbound CL domains. SEM micrographs elucidated that FG/CL (8 : 2) blend film was slightly rougher than FG film, but no signs of phase separation between film components were observed, thereby confirming its prospective use as food packaging material.