Effect of processing conditions on the prebiotic activity of commercial prebiotics

The functional prebiotic stability of fructooligosaccharides (FOS) and inulin was determined using a prebiotic activity assay. Prebiotic activity scores were determined based on the change in cell biomass of Lactobacillus paracasei 1195 on the prebiotic relative to that of Escherichia coli under equivalent conditions. Prebiotics were dissolved in citrate–phosphate buffer solutions (10% FOS or 2% inulin), and then exposed to each of three treatments simulating food processing conditions: low pH (pH 3–6), heat at low pH (30 min at 85 °C, pH 4–7), and Maillard reaction conditions (up to 6 h at 85 °C with 1% glycine, pH 7). Prebiotics were considered functionally stable if their score was unchanged after treatment. In general, only heating at low pH caused a significant reduction in prebiotic activity, with one of the FOS products being the least stable. The other conditions caused little change in activity. These results provide a basis for selecting prebiotics for use as functional food ingredients and for predicting the extent to which processing affects prebiotic activity.