Abstract:Red beet polysaccharide（RBP） was extracted from red beet by water extraction and alcohol precipitation to explore its structural characterization and in vitro fermentation properties. The structure of RBP was characterized by high performance liquid chromatography （HPLC）， ion exchange chromatography and Fourier transform infrared spectroscopy （FT-IR）， and the fermentation properties were investigated by in vitro digestion and fermentation experiments of porcine colon. The results revealed that the average molecular weight of RBP was 46.3 kDa， and it contained arabinose， galactose， mannose， rhamnose and glucose with molar ratio of 6.7∶4.6∶1.7∶1.0∶1.0. The peaks at 1 628.2 cm-1 and 1 740.1 cm-1 were derived from carboxylate stretching band and ester carbonyl groups， respectively， which showed a pectin-like structure with a relatively low degree of esterification（30.10%）. The in vitro fermentation experiments suggested that RBP could be digested by intestinal microorganisms， promoting the growth of some health-promoting bacteria like Lactobacillus，Firmicutes and Bateroidetes while inhibiting some pathogenic bacteria like Proteobacteria and Streptococcus.