Comparative analysis of the prebiotic effect of Fructooligosaccharides and Raffinose oligosaccharides on nutraceutical and sensory properties of soymilk fermented with mixed cultures of Lacticaseibacillus rhamnosus and Weissella confusa 30082b

High potential is attributed to the concomitant use of probiotics and prebiotics in a single food product, called "synbiotics," where the prebiotic component distinctly favours the growth and activity of probiotic microbes. This study implemented a detailed comparison between the prebiotic effect of Fructooligosaccharides (FOS) and Raffinose Oligosaccharides (RFOs) on the viable count of bacteria, hydrolysis into monosaccharides for the biosynthesis of postbiotic Short Chain Fatty Acids and sensory attributes of soymilk fermented with 1% (v/v) mixed cultures of Lacticaseibacillus rhamnosus JCM 1136 and Weissella confusa 30082b. The highest viable count of 1.21×10 9 CFU/ml was observed in soymilk with 3%RFOs added as a prebiotic source compared with MRS broth with 3% RFOs (3.21×10 8 ) and 3%FOS (6.2 ×10 7 CFU/ml) when replaced against glucose in MRS broth. Raffinose and stachyose were extensively metabolised (4.75 and 1.28-fold decrease, respectively) in 3%RFOs supplemented with soymilk, and there was an increase in glucose, galactose, fructose (2.36,1.55, 2.76-fold respectively) in soymilk supplemented with 3% FOS. Synbiotic soymilk with 3%RFOs showed a 99-fold increase in methyl propionate, while the one supplemented with 3%FOS showed an increase in methyl butyrate. The highest acceptability was for soymilk fermented with 2%RFOs + 2%FOS + 2% Table sugar + 1% vanillin (7.87 ± 0.52) with high Mouth feel, product consistency, taste, and flavour. This study shows that simultaneous administration of soy with probiotic bacteria and prebiotic oligosaccharides like FOS and RFOs enhance the synergistic interaction between them, which up-graded the nutritional and sensory quality of synbiotic soymilk.