Enzymatic Preparation of Phenolic Acid-Pectin and Its Antioxidant and Antibacterial Activities

This study explored the impact of enzymatic grafting modification on the structure and functional properties of pectin, aiming to provide a scientific foundation for the development of novel food packaging materials with bioactive properties. Using lipase as a catalyst, p-hydroxybenzoic acid and gallic acid were grafted onto pectin molecules. The structure of the modified pectin was characterized using ¹H NMR, FTIR, and XPS analytical techniques, and its antioxidant and antibacterial activities were evaluated. The results showed that the grafting rates of p-hydroxybenzoic acid-modified pectin (Hb-Pe) and gallic acid-modified pectin (Ga-Pe) reached 21.8% and 22.9%, respectively. Notably, compared to unmodified pectin, Ga-Pe exhibited significantly (P<0.05) enhanced DPPH free radical scavenging capacity (69.6%) and β-carotene bleaching inhibition capacity (65.5%), while the improvement in antioxidant activity of Hb-Pe was limited, with the two indicators being only 5.54% and 28.6%, respectively. Furthermore, the inhibition zone diameters of the two modified pectins against Escherichia coli and Staphylococcus aureus were 15.7, 13.3 mm (Hb-Pe) and 16.6, 12.6 mm (Ga-Pe), respectively, which were significantly (P<0.05) higher than those of unmodified pectin. This study confirms that enzymatic grafting modification can effectively enhance the bioactivity of pectin, providing a new approach for extending the shelf life of food products.