Fructooligosaccharides exhibit more rapid fermentation than long-chain inulin in an in vitro fermentation system

This study investigated how chain length affects fermentation properties of fructooligosaccharides (FOSs) and inulin (IN). Chain lengths of FOSs and IN vary from an average degree of polymerization (DP) of 3 to greater than 20. Three samples classified as FOSs (samples A, B, and C) and 3 samples classified as IN (samples D, E, and F) were fermented via an in vitro batch method with human fecal inoculum as the source of microbes. Samples were removed at 0, 4, 8, 12, and 24 hours for total short-chain fatty acid (SCFA), acetate, propionate, and butyrate measurement via gas chromatography. Sample chain length did not affect SCFA concentrations in a predictable manner. Sample E (90%-94% DP > 10, 6%-10% DP = 1-2), a mixture of long-chain IN and short-chain FOS, produced significantly more total SCFA and acetate than the other samples. Sample F (DP > 20), the longest-chain IN, produced the lowest concentration of butyrate at 24 hours. The rate of FOS fermentation was higher than IN fermentation during 0 to 4 hours for all SCFAs, and the rate of IN fermentation was higher than FOS fermentation during 12 to 24 hours for all SCFAs. Chain length affects in vitro fermentability, with short chains being rapidly fermented and long chains being steadily fermented. Clinical studies should follow this work to verify if these differences exist in vivo.