Active packaging coating based on agarose grafted with benzoic acid derivatives: Preparation, characterization and application in fish preservation

Agarose based on gel strength can not meet the needs of diverse applications, and the structural modification of agarose is helpful to improve its functional properties and promote the economic benefits of the agarose industry chain. This study focuses on making agarose as an active packaging material with specific functions. Agarose was modified with p-hydroxybenzoic acid (Ph) and 3, 4-dihydroxybenzoic acid (Da) to produce agarose derivatives with grafting rates of 4% and 12% (Ph-Ag@4%, Ph-Ag@12%, Da-Ag@4%, and Da-Ag@12%). Characterization techniques confirmed the successful introduction of Ph and Da onto agarose, with grafting occurring at the C-6 position in d-galactose. Both Ph-Ag and Da-Ag exhibited significantly enhanced antioxidant and antibacterial properties. Da-Ag@12% showed remarkable improvements in DPPH and ABTS radical scavenging activities from 0% to 66.01% and 2.49%–84.73%, respectively. Ph-Ag@12% exhibited inhibition rates of 100% against Escherichia coli and Staphylococcus aureus. After modification, Ph-Ag and Da-Ag maintained good gelling and film-forming properties. Fish preservation experiments revealed both Ph-Ag and Da-Ag coatings effectively suppressed microbial growth, slowed down lipid oxidation, minimized water loss, and maintained the texture and appearance of fish meat. These coatings improved fish meat quality and extended its shelf life, with Da-Ag@12% showing the most promising results.