Fabrication of polyvinyl alcohol/soy protein isolate-based composite nanofilm for preserving Chinese cabbage

A composite film based on a polyvinyl alcohol (PVA)/soy protein isolate (SPI) loaded with ε-polylysine (ε-PL) was prepared via electrospinning and utilized to preserve the freshness of Chinese cabbage. The active films were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and differential scanning calorimeter. Further molecular dynamic simulations results confirmed that PVA can spontaneously form stable complexes with SPI, which was mainly driven by the combined contribution of van der Waals interactions, electrostatic interactions and non-polar solvation energy. The binding of PVA via its hydroxyl groups interactions with many residues of protein surface resulted in the change of protein conformation and solvent assessable surface area. The SPI/PVA nanofiber film loaded with 8 % ε-PL exhibited stronger antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), with inhibition zone diameters measuring 13.93 ± 0.14 mm and 17.54 ± 0.17 mm, respectively. Its density was measured at 0.32 ± 0.03 g/cm³, with a swelling ratio of 199.36 ± 23.54 %, solubility of 25.87 ± 0.31 %, and a water vapor permeability of 0.53 ± 0.07 g·mm/m²·h·pa. The utilization of 8 % ε-PL-loaded SPI/PVA nanofiber film effectively prevented the weight losses, chlorophyll, carotenoids, and lutein reduction of Chinese cabbages. Overall, this study uncovered the molecular mechanisms underlying the successful fabrication of ε-PL/SPI/PVA nanofiber film and further demonstrated its potential for Chinese cabbages preservation.