Abstract: In this work, hydrothermal treatment was carried out on a commercial pectic polysaccharide, and the antioxidant activities of the degradation products were investigated. The results showed that the optimal degradation conditions were found to be treatment at 140 ℃ and pH 6 for 30 min. Under these conditions, the efficiency of degradation was 46.2%. On this basis, the degradation products were fractionated by ethanol precipitation into three fractions (S1, S2 and S3). The weight average molecular masses of S1, S2 and S3 were 13.4, 7.5 and 5.7 kDa, respectively. The antioxidant activities of the pectic polysaccharide and the three degradation products were evaluated. The results showed that the 1,1-diphenyl-2- picrylhydrazyl (DPPH) radical scavenging rate of S1 was 49.8%, which was 4 times as high as that of the pectin, while the superoxide anion scavenging rate of S3 was 58.7%, which was 10 times as high as that of the pectin. These results indicated that the hydrothermal degradation of pectic polysaccharides could significantly improve its antioxidant activity. This study provides a theoretical basis for the efficient utilization of pomace wastes.

Key words: pectic polysaccharide, hydrothermal treatments, degradation products, ethanol fractionation, molecular mass, antioxidant activity