Fractionation and structural characterization of polysaccharides derived from red grape pomace

Abstract

Polysaccharides were recovered from red grape pomace by hot water extraction and then subjected to deproteinization, decolorization, fractionization, and characterization. The extraction process conferred a crude polysaccharide yield of 8.45 % (w/w) and the highest decolorization rate of 63.12 % was obtained by soaking the crude polysaccharide solution with 0.20 g/mL HPD-300 macroporous resin for 3 h. Separation with the anionic DEAE Fast Flow column generated four fractions, which were negatively charged according to zeta potential measurement. All the fractions contained uronic acid and their weight-average molecular weights were within the range 2 × 106–4 × 106 Dal. The most abundant fraction GPP-3 was composed of arabinose, xylose, mannose, glucose, and galactose in molar ratio 8.05:1.37:2.85:1.30:7.81 and rhamnose was also present according to FTIR and NMR analysis. AFM observation revealed that aggregation occurred in GPP-3, while the Congo red and β-elimination tests indicated the existence of triple helix and -O- linkage in the fraction. Hence, red grape pomace is a potential source of water-soluble polysaccharides and their bioactivity needs further study.