Effects of grafting methods and raw materials on the physicochemical properties and biological activities of phenolic acids grafted oat β-glucan

Caffeic acid (CA) and gallic acid (GA) were grafted onto oat β-glucan (OG) and hydrolyzed oat β-glucan (OGH) through CDI and EDC/NHS methods. Graft modification decreased the crystallinity and thermal stability of the conjugates, but the antioxidant and antibacterial activities were significantly improved. The antioxidant and bacteriostatic activities of the conjugates prepared by the EDC method were better than those of the CDI method, and the biological activities of GA-conjugates were better than those of CA-conjugates. The lower the molecular weight of oat β-glucan, the higher the biological activities for its grafted conjugates, and EDC-GAOGH showed best DPPH (89.78%) and ABTS (92.32%) scavenging activities, and strongest inhibition effects against pathogenic microbes Staphylococcus aureus and Escherichia coli compared to other conjugates, which indicated that EDC-GAOGH has potential application value in food biological preservation.