Dynamic variation in biochemical properties and prebiotic activities of polysaccharides from longan pulp during fermentation process.

Lactic acid bacteria fermentation is an important processing technology for fruits and vegetables. Bioactive compounds such as polysaccharides are altered during the fermentation process. Polysaccharides from longan pulp (LPs) were extracted after different fermentation times and their physicochemical and prebiotic properties were investigated, such as longan polysaccharides named LP-0 and LP-12 means they were extracted from longan pulp fermented for 0 and 12 h, respectively. The yield, contents of neutral sugar and uronic acid, molecular weight (Mw), and monosaccharide composition of LPs were significantly changed with different fermentation times. Specially, the yield and uronic acid content of LPs were first increase and then decline. LP-12 contained the smallest Mw (108.71 ± 5.55 kDa) of the tested LPs (p < 0.05). When compared with unfermented LP-0, the glucose molar percentages of fermented LPs declined, while those of rhamnose and galactose increased, except for LP-6. Fermented LPs also exhibited a stronger stimulatory effect on Lactobacillus strain proliferation, with the proliferative effect of LP-12 being the strongest (p < 0.05). These results suggest that lactic acid bacteria fermentation can change the physicochemical properties and enhance the prebiotic activities of polysaccharides from longan pulp.