Developing a bio-based packaging film from soya by-products incorporated with valonea tannin

The waste production from plastic packaging causes serious environmental problems and resource issues. The most effective way to solve these problems is to develop eco-friendly packaging. In this work, soy protein isolate (SPI) films were developed incorporated with 0%, 5%, 10%, 15% (w/w, based on SPI) valonea tannin at pH 8 and 10. Valonea tannins increased protection against UV light and decreased the transparency of SPI films (p < 0.05). Antioxidant properties of SPI films improved as determined by 2, 2-diphenylpicrylhydrazyl (DPPH) radical scavenging activity. The addition of valonea tannins increased tensile strength (TS) and decreased percentage of elongation at break (% E) of SPI films (p < 0.05). The SPI films with 10 w/w% valonea tannin at pH 8 and 10 had the highest TS. Due to the highly hydrophilic nature of valonea tannins, the water vapor permeability (WVP) of SPI films was increased; however, oxygen permeability (OP) reduced (p < 0.05). Compared to SPI films at pH 8, films at pH 10 had higher transparency, TS, and % E and lower OP, WVP, and DPPH radical scavenging activities. The results revealed that SPI films show a great potential to be used as antioxidant packaging films for food.