Development and characterization of antioxidant composite films based on starch and gelatin incorporating resveratrol fabricated by extrusion compression moulding

Starch/gelatin (SG) films incorporated with resveratrol (RES) at various concentrations (0%–20%, w/w, on the weight of starch and gelatin) were developed via thermal extrusion followed by compression moulding. The SG based films were characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy, together with the determination of optical, physical, thermal, and antioxidant properties of the films. SEM images showed the SG films containing RES had a higher surface roughness than that without RES, which was also confirmed by the three-dimensional surface topography images. The FTIR analysis revealed the existence of physical interactions among starch, gelatin, and RES through hydrogen bonding. The incorporation of RES significantly increased the thickness, opacity, and tensile strength of the films, while decreasing their transmittance, water solubility, water vapor and oxygen permeability. Furthermore, the elongation at break, surface hydrophobicity and thermal stability of the films also enhanced to some extent after addition of RES. More importantly, the composite films showed excellent antioxidant activity proportional to the RES concentration, and all films showed good anti-permeate property for oil without or with RES. Consequently, the SG film containing 20% RES with the highest oxygen barrier property and antioxidant activity could effectively reduce oxidative rancidity of soybean oil stored at 50 °C for 24 days when compared to SG film without RES and control sample (without film). To sum up, the thermoplastic processed SG films incorporating RES exhibited adequate properties for food packaging such as oil products which are highly susceptible to oxidation.