Effects of dielectric barrier discharge plasma modification on structure, physicochemical and functional properties of watermelon peel pectin

Dielectric barrier discharge (DBD) plasma is a simple and green method for biomacromolecule modification, and watermelon peel pectin (WMP) has broad application prospect in food industry. This study investigated the effects of DBD plasma under different voltage (20 V, 40 V) and treatment time (1 min, 3 min, 5 min) on the structural, physicochemical and functional properties of WMP. The DBD plasma treatment (40 V, 5 min) exhibited the lowest molecular weight (Mw, 199.06 +/- 8.05 kg/mol), average molecular weight (Mn, 27.15 +/- 1.75 kg/mol), degree of methylation (DM, 36.18 +/- 0.65%) and acetylation (DA, 2.33 +/- 0.09%) of WMP. Moreover, DBD plasma treatment could degrade the main chain of WMP, and had less effect on the side chain. The microstructure of WMP changes from dense block structures to porous and thin fibrous, while pectin molecules are degraded and oxidized after DBD plasma treatment. Compared with the native WMP, DBD plasma treatment at different modes effectively increased the thermal stability, antioxidant ability, solubility and emulsifying properties of WMP, but lowered its shear thinning fluid behavior and liquid-like property. Conclusively, our results show that DBD plasma is a promising way to modified and improve functional properties of WMP.