Active packaging coatings based on agarose caffeate: Preparation, characterisation, and application in grass carp (Ctenopharyngodon idellus) preservation

Caffeic acid was grafted to agarose by a nonradical synthesis method to improve the functional properties of agarose and its application value in food preservation. Structural characterization showed that the carboxyl group of caffeic acid was successfully grafted to the C6-OH of D-galactose in agarose, and the highest grafting ratio could reach 12.18 %. Incorporating caffeic acid significantly increased the antioxidant and bacteriostatic activities. With the increase in grafting ratio from 0 % to 12.18 %, the scavenging ratio of DPPH increased from 0 % to 50.09 %, and the inhibition ratio of β-carotene bleaching increased from 7.49 % to 72.21 %. The bacteriostatic ratio of agarose caffeate (Cf-Ag) against Escherichia coli and Staphylococcus aureus could reach 100 %. The fish preservation test indicated that Cf-Ag had positive effects on inhibiting bacterial growth and fat oxidation, reducing the water loss, and prolonging the overall quality of grass carp fillet during refrigeration, which was more effective than native agarose in extending the shelf life of fish.