Bioadhesive and antibacterial edible coating of EGCG-grafted pectin for improving the quality of grapes during storage

Many hydrophilic edible coating materials with antioxidant and antibacterial activities usually have weak adhesion on waxy hydrophobic surfaces of fruits and vegetables, seriously restricting the application of edible coating in food preservation. In this work, Epigallocatechin gallate (EGCG) was grafted with pectin by free radical mediated reaction to attempt to enhance the adhesion of pectin on the hydrophobic surface of fruits and vegetables through the unique pyrogallol structure of EGCG. The effects of covalent grafting of EGCG with different types of pectin on its physicochemical properties, antioxidant activity, and antibacterial activity were investigated. The results found that low methoxy pectin (LMP) grafted with EGCG (LMP-EGCG) coating could significantly reduce the weight loss, decrease phenol content and the activity of polyphenol oxidase of grapes (p < 0.01), and inhibit the lipid oxidation and inhibit the growth of microorganisms of grapes during post ripening (p < 0.01). Finally, the contact angle and solubility in water were used to evaluate the adhesion properties of LMP-EGCG on the surface of grapes, and the results showed that the covalent grafting of EGCG significantly enhanced the wetting and adhesion properties of pectin coatings on the surface of grape skin. Collectively, these results suggested that the covalent grafting of EGCG endowed the adhesion ability of edible coating of pectin on the hydrophobic surface of fruits and vegetables, which had broad application potential in the field of fruit and vegetable fresh-keeping.