Protocatechuic aldehyde-grafted chitosan copolymer: a focus on its physicochemical properties and application potential in fresh shrimp preservation

The safety of aquatic products is a significant concern due to their vulnerability to contamination by pathogenic bacteria, which cause foodborne diseases. Therefore, a protocatechuic aldehyde-grafted chitosan (PCA-CS) copolymer was developed, which can be used in practical antimicrobial applications for aquatic products to improve the safety. Analytical techniques, including FTIR analysis, transmission electron microscopy, and particle size/zeta potential measurements, confirmed the formation of a stable PCA-CS copolymer. The FTIR spectral signatures (e.g., C=N stretching at 1550 cm⁻¹) unequivocally demonstrated covalent grafting via a Schiff base reaction. Compared with PCA alone, the PCA-CS copolymer has exhibited superior temperature stability, antioxidant capacity, and light transmission, as well as enhanced antibacterial activity against Vibrio parahaemolyticus at low concentrations. Practical experimental findings have demonstrated that the PCA-CS copolymer, at a low concentration of 32.5 μg/mL, outperformed high concentrations of PCA (300 μg/mL) in preserving shrimp for 7 days. It effectively inhibited bacterial growth, stabilized pH, and preserved color. The present study demonstrated the PCA-CS copolymer's remarkable stability and antibacterial properties, suggesting its potential as a safe and effective preservative to improve the safety and shelf life of aquatic products.