Characterization and antioxidant activity of polysaccharides obtained from ginger pomace using two different extraction processes

In this study, two different processes of hot water (HW) and ultrasonic-assisted (UA) for the extraction of polysaccharide from ginger pomace (GPPs) were employed under their respective best parameters, and the characterization and antioxidant activity of the purified polysaccharide (HW-GPP1, HW-GPP2, HW-GPP3, and UA-GPP1, UA-GPP2, UA-GPP3, respectively) were analyzed. The data implied that the yield of the polysaccharide obtained by UA was higher than that of HW. Meanwhile, two kinds of GPPs possessed the different preliminary structural characteristics including molecular weight distributions, total sugar and protein content, uronic acid content, while similar monosaccharide compositions and sulfuric radical contents. In vitro antioxidant activity assays indicated that UA-GPP3 showed the strongest scavenging abilities on DPPH radicals, while UA-GPP2 possessed the strongest scavenging abilities on hydroxyl and superoxide radicals. Moreover, the antioxidant activity of each fractions of GPPs extracted by UA was better than that of the corresponding fractions of GPPs extracted by HW. These results showed that UA was more beneficial to enhance the extraction yields of the polysaccharides, and also resulted in GPPs with higher bioactivity. Therefore, it indicated that UA-GPPs could be used as a potential natural antioxidant. Accordingly, the ginger pomace could be used as a potential source for natural antioxidant.