Development of sunflower protein isolate emulsion-based edible composite films with the addition of potato starch: Barrier, mechanical, thermal, and morphological properties

Edible composite films from sunflower protein isolate emulsion (SPIE) and potato starch were prepared at different ratios by the casting method. The effect of starch addition on the barrier, mechanical, thermal, and morphological properties were investigated. The maximum tensile strength and minimum water vapor permeability was observed for composite film developed at 50:50 (SPIE:PS) ratio. Transparency of sunflower protein isolate emulsion film was observed to be lower as compared to all other composite films. Total color difference values increased with increase in the concentration of starch. X-ray diffraction of SPI emulsion film and composite films indicated amorphous structure of films. SPI emulsion film exhibited high degree of porosity. With the addition of starch, porosity of films decreased, and compactness increased. Differential scanning calorimetry curves of all films indicated melting temperature in the range of 87.22–157.21°C and enthalpy in the range of 39.86–110.94 J/g. Overall, composite films were compact, nonporous and smooth as compared to film prepared from native SPI emulsion.