Bio-based films prepared with soybean by-products and pine (Pinus densiflora) bark extract

The increasing awareness of environmental protection associated to plastic waste has promoted the developments of biopackaging in food industry. Pine (Pinus densiflora) bark extract (PBE) obtained from waste dry bark from lumber processing is a good source of oligomeric procyanidins and has excellent antioxidant activity. In this study, bio-based antioxidant films were prepared by incorporating different concentrations of PBE (0 20, 50, and 80 g kg−1) into soy protein isolate (SPI) matrix and analyzed in terms of structure, as well as physical, mechanical, and antioxidant properties. Scanning electron microscopy results suggested that the structures of the films with PBE were rougher. X-ray diffraction analysis indicated cross-linking interactions formed between the phenolic hydroxyl group in PBE and the amino groups in the SPI matrix. Thermogravimetric analysis indicated that PBE enhanced the thermal stability of the films. Moreover, the addition of 50 g kg−1 PBE decreased the moisture content, water vapor permeability, and oxygen permeability of the SPI films by 30.7%, 9.1%, and 31.6%, respectively. The PBE-containing films exhibited good light-barrier property. They also exhibited high tensile strength and low elongation at break. Furthermore, PBE markedly increased the antioxidant activity of the SPI films. Antioxidant SPI films with PBE have potential application in food packaging.