Enhanced physico-mechanical, barrier and antifungal properties of soy protein isolate film by incorporating both plant-sourced cinnamaldehyde and facile synthesized zinc oxide nanosheets.

In order to exploit multifunctional packaging material, soy protein isolate (SPI) based biocomposite films incorporated with plant-sourced cinnamaldehyde (CIN) and zinc oxide nanoparticles (ZnO NPs) synthesized by a liquid precipitation method were prepared and characterized. The functional actions between cinnamaldehyde and zinc oxide nanoparticles on the physical, mechanical and antifungal properties of the obtained film samples were subsequently investigated in this study. Results indicated that the addition of CIN produced a SPI composite film with low tensile strength (TS) and elongation at break (EAB), but these alterations were the opposite in SPI + ZnO film. Moreover, the incorporation of CIN or ZnO NPs to SPI matrix affected differently color parameters, oxygen permeability and storage modulus of the resulting composite films. Among regular SPI film and composite film with one added ingredient, SPI-based bionanocomposite film containing CIN and ZnO NPs displayed the best barrier capacities, mechanical properties and antifungal activities. Its values of tensile strength and breaking elongation are 1.26-fold and 1.23-fold than that in the pristine SPI film, respectively. Meanwhile, the oxygen permeability and water permeability for SPI + CIN + ZnO film are 66.1% and 54.8% of that in regular SPI film, respectively. Moreover, the antifungal activity of the composite film with two added ingredients is 1.56-fold and 1.24 fold stronger than those of SPI + ZnO and SPI + CIN films. These investigations reveal that the developed SPI + CIN + ZnO film could be utilized as an ideal packaging matrix for food preservation.