Synergistic effect and mechanism of cellulose nanocrystals and calcium ion on the film-forming properties of pea protein isolate.

The current serious environmental problems have greatly encouraged the design and development of food packaging materials with environmental protection, green, and safety. This study aims to explore the synergistic effect and corresponding mechanism of cellulose nanocrystals (CNC) and CaCl to enhance the film-forming properties of pea protein isolate (PPI). The combination of 0.5 % CNC and 4.5 mM CaCl resulted in a 76.6 % increase in tensile strength when compared with pure PPI-based film. Meanwhile, this combination effectively improved the barrier performance, surface hydrophobicity, water resistance, and biodegradability of PPI-based film. The greater crystallinity, viscoelasticity, lower water mobility, and improved protein spatial conformation were also observed in CNC/CaCl composite film. Compared with the control, the main degradation temperature of composite film was increased from 326.23 °C to 335.43 °C. The CNC chains bonded with amino acid residue of pea protein at specific sites via non-covalent forces (e.g., hydrogen bonds, Van der Waals forces). Meanwhile, Ca promoted the ordered protein aggregation at suitable rate and degree, accompanied by the formation of more disulfide bonds. Furthermore, proper Ca could strengthen the cross-linking and interaction between CNC and protein, thereby establishing a stable network structure. The prepared composite films are expected to be used for strawberry preservation.