Fabrication of chitosan/black rice anthocyanin composite films cross-linked with dialdehyde pullulan for shrimp...

Food freshness indicating films were produced by using chitosan (CS) as matrix, black rice anthocyanin (BRA) as pH-sensitive colorant, and dialdehyde pullulan (DAP) as cross-linking agent. The impact of DAP cross-linking on the structural characteristics, functionality and shrimp freshness indicating potential of CS/BRA films was determined. Cross-linking between CS and DAP resulted in more compact films. The transparency, tensile strength, elongation at break and thermal stability of CS/BRA films were improved by DAP. After cross-linking with DAP, the films exhibited lower moisture content, surface wettability, water vapor permeability and anthocyanin releasing ratio. The color changes of CS/BRA films in response to pH or ammonia were delayed by DAP. However, the color reversibility and color stability of CS/BRA films were unchanged by DAP. Notably, the shrimp freshness indicating accuracy of CS/BRA films was improved by DAP. This study revealed that DAP cross-linking remarkably enhanced the intelligent packaging performances of CS/BRA films.