Effects of crude Sphallerocarpus gracilis polysaccharides as potential prebiotics on acidifying activity and growth of probiotics in fermented milk

Sphallerocarpus gracilis is a medicinal and edible plant in China with high nutritional value. This paper reports on the potential application of crude polysaccharides from Sphallerocarpus gracilis (SGP) as prebiotics. The crude SGP was characterized, and its digestibility, positive effects on acid production and growth of probiotics during milk fermentation and shelf life were also investigated. It was observed that the contents of total carbohydrates, reducing sugar and protein of crude SGP were 72.62 ± 0.32%, 18.56 ± 0.16% and 0.12 ± 0.01%, respectively. Crude SGP had lower ( P < 0.05) hydrolysis degree (1.52% and 3.04%, respectively) in the simulated gastrointestinal fluid and α-amylase solution than that of fructooligosaccharides (2.48% and 3.87%, respectively) and inulin (2.24% and 3.43%, respectively). It was found that crude SGP could both improve the acidifying activity and growth of Streptococcus thermophilus , Lactiplantibacillus plantarum and Lacticaseibacillus rhamnosus during the milk fermentation ( P < 0.05). During shelf life, the viable probiotics population in fermented milk supplemented with crude SGP was notably larger ( P < 0.05) than that of fermented milk containing fructooligosaccharides or inulin. Overall, these findings clearly indicate that the crude SGP has a potential to be exploited as novel prebiotics. • The prebiotic activity of crude SGP was evaluated. • Crude SGP showed high stability in the artificial human gastrointestinal fluid. • Crude SGP increased the acidifying and growth of the tested probiotics. • Crude SGP improved the survival rate of the tested probiotics during the shelf life.