Polysaccharides obtained from bamboo shoots (Chimonobambusa quadrangularis) processing by-products: New insight into ethanol precipitation and characterization

Chimonobambusa quadrangularis polysaccharides (CPS) were extracted by ultrasonic-assisted extraction from bamboo shoots (C. quadrangularis) processing by-products. Three polysaccharide fractions, CPS70, CPS75 and CPS80, were obtained by precipitation at final ethanol concentrations of 70%, 75% and 80%, respectively. The physicochemical characterization and chemical antioxidant activities of the three polysaccharide fractions were compared on the basis of HPLC, FT-IR, XRD, TGA, and antioxidant measurements in vitro. The results suggested that ethanol concentrations used for precipitation of CPS can affect its physicochemical and associated functional properties, and antioxidant activities. Compared with CPS70 and CPS80, CPS75 had lower glucose content, higher total sugar content, and higher protein and uronic acid contents. The CPS70 and CPS80 were composed of Man, Rha, GlcA, Glc, Gal, Xyl and Ara, but none of them were found to contain GalA. In contrast, CPS75 consisted of Man, Rha, GlcA, GalA, Glc, Gal, Xyl and Ara. CPS75 had the lowest medium-high-molecular-weight value (116.53–118.18kDa) and the highest medium-low-molecular-weight value (21.30–22.68kDa). Meanwhile, CPS75 exhibited better functional properties including the repose angle, swelling capacity (SC), water retention capacity (WRC), and oil retention capacity (ORC). Moreover, CPS75 possessed higher scavenging capacities on DPPH, hydroxyl and ABTS radicals, higher oxygen radical absorbance capacity (OARC), higher metal chelating activity, and more significant reducing power. According to the results above, a final ethanol concentration of 75% could be chose to precipitate polysaccharides from bamboo shoots (C. quadrangularis) processing by-products. In summary, it is strongly recommended that the ethanol concentration employed in precipitation of natural polysaccharides could be optimized in advance.