Influence mechanism of wheat bran cellulose and cellulose nanocrystals on the storage stability of soy protein isolate films: Conformation modification and molecular interaction perspective

This study aims to elucidate the changes and corresponding mechanisms of storage stability of soy protein isolate (SPI) films strengthened via wheat bran cellulose (WBC) and cellulose nanocrystals (CNC). The incorporation of WBC and CNC improved the mechanical strength, water resistance, water vapor and visible light barrier abilities of stored SPI-based films to varying degrees. Higher crystallinity and lower water mobility were observed in the composite films. WBC molecules reduced the irregular pores and cracks within the internal structure of the film through physical filling and non-covalent interactions, involving hydrogen bond and van der Waals force. In contrast, uniformly distributed CNC cross-linked with amino acid residues at specific binding sites under noncovalent forces. Furthermore, CNC induced the secondary conformation of proteins to transform from alpha-helix to beta-sheet and enhanced the hydrophobic interaction, which promoted the establishment of a stable network structure and thus extended the storage stability of SPI-based films.