Preparation and Application of Antioxidative Chitosan/Soybean Protein Isolate Composite Edible Membrane

Taking chitosan (CS) and soybean protein isolate (SPI) as composite membrane substrates and natural antioxidants as active substances, an edible active preservative film with inhibitory effect on lipid oxidation was developed. After optimizing the type and concentration of antioxidants through the mechanical properties, microstructure, physical properties, and antioxidant properties of the composite membrane, the preservation effect of the composite membrane on walnut oil was investigated. Results showed that, eight antioxidants significantly improved the oxygen-barrier ability of the composite membranes (P<0.05). Especially, the peroxide value of walnut oil was reduced by about 80% and maintained excellent mechanical properties with the addition of astaxanthin, grape seed extracts and vitamin C. When the addition of astaxanthin was 0.3%, the composite membrane exhibits the best performance, then the tensile strength, elongation at break, DPPH free radical scavenging capacity and water vapor permeability of the composite membrane were 6.546 MPa, 69.962%, 80.1%, 1.21 g∙mm/m²∙h∙kPa, respectively. Scanning electron microscopy revealed that the surface of the membrane was smooth, regular and uniform. Fourier transform infrared spectroscopy showed that membrane-forming materials were extremely compatible. The differential scanning calorimeter analysis showed that the composite membrane had the highest thermal enthalpy, reaching 233.940 J/g, with the best thermal stability. When the walnut oil was coated with a composite membrane containing astaxanthin, the oil’s peroxide value was reduced by 81.8%, conjugated diene by 44.4% and conjugated triene values by 66.4% compared to the control. Chitosan/soybean protein isolate composite membrane with astaxanthin significantly delayed the process of walnut oil oxidation.