Physicochemical characterization, rheological and antioxidant properties of three alkali-extracted polysaccharides from mung bean skin

The properties of polysaccharides are closely related to their extraction and preparation methods. However, studies on the effect of alkali concentration on the properties of polysaccharides during alkali extraction are scarce. In this study, three alkali-extracted polysaccharides from mung bean skin (MBP) by different alkali concentrations (0.5%, 1.0%, 2.0%, w/v, MBP0.5, MBP1.0 and MBP2.0) were successfully obtained. The effects of alkali concentration on the extraction rate, microstructure, rheological properties, antioxidant activity and cell proliferation activity of MBP were investigated. The results showed that the alkali extraction method can break the ester and hydrogen bonds between polysaccharides, thus three alkali-extracted polysaccharides had higher extraction yields than polysaccharide extracted by hot water (MBPW), and MBP1.0 extraction rate of 3.64%. Moreover, comparing with MBPW, three alkali-extracted polysaccharides had lower molecular weights, particle sizes and better thermal stability. In addition, MBP0.5 had better antioxidant activity due to its higher galacturonic acid content and lower molecular weight, MBP1.0 and MBP2.0 had a tight structure, flat surface, resulting in a strong gel network structure. Cell experiments showed that MBPs had different degrees of proliferative effects on RAW264.7 and L-02. This study will provide some research ideas for the extraction of plant polysaccharides by alkaline methods.