Improved barrier, mechanical and antioxidant properties of pH-responsive film by incorporating dialdehyde starch and anthocyanins into rice protein/sodium alginate.

This study aimed to develop rice protein/sodium alginate (RP/SA) pH-responsive films with enhanced properties by incorporating dialdehyde starch (DAS) and Lycium ruthenicum anthocyanins (LRA) and the film was applied to monitor the fruit freshness. The effect of the DAS and LRA content on the morphology, mechanical, water barrier, oxygen barrier, ultraviolet-blocking and thermal stability properties of RP/SA-based films was investigated. The best water vapor permeability of the film was 3.33 g·mm/(m·d·kPa) with 10 % DAS. With increasing the DAS content from 0 % to 20 %, the tensile strength of the film was increased by 66.3 % compared with that of the film without DAS, while the thermal stability, oxygen barrier and ultraviolet light barrier properties were significantly enhanced. These results may be due to the formation of a compact structure observed by scanning electron microscopy, and stronger hydrogen bonding interactions and lower binding energy in the RP/SA/DAS/LRA system obtained by Fourier transform infrared spectroscopy, X-ray diffraction and molecular dynamics simulation. The RP/SA/DAS/LRA film had 51.6 times higher antioxidant property than the film without LRA and exhibited significant color variations with changes in fresh-cut cantaloupe quality. The developed RP/SA-based films with improved properties are potential intelligent food packaging materials.