Prebiotic potential and chemical characterization of the poly and oligosaccharides present in the mucilage of Opuntia ficus-indica and Opuntia joconostle

•Mucilages from two Opuntia spp. were separated into three fractions.•Two fractions include high M̅w heteropolysaccharides (4.0 × 103 to 8.0 × 105 g∙mol−1).•Previously undescribed oligosaccharides were found bound to the mucilage.•Complex-structured β-(1–4) linked heterogalactooligosaccharides were found.•Most of the carbohydrate fractions show prebiotic potential. The mucilage extracted from the convection-dried cladodes of O. ficus-indica and O. joconostle, two species of economic importance, delivered three fractions after methanol precipitation. Two were composed of high molar mass polysaccharides, and one included water-soluble mono-, di-, and oligosaccharides. The large polysaccharides have a molar mass range of 4.0 × 103 to 8.0 × 105 g·mol−1 and are consistently composed of galactose, arabinose, xylose, and rhamnose; however, the content of galacturonic acid was different between both fractions and species. Their fermentability by selected probiotics was relatively low, 11–27 % compared to glucose, and decreased with increasing levels of galacturonic acid in the molecules. In the third fraction, previously unreported oligosaccharides were found. These include simple- and complex-structured galactooligosaccharides with arabinosyl-, xylosyl- and galacturonosyl acid residues. Their fermentability by prebiotic species can be ascribed more to their structural characteristics and monosaccharide composition than their molecular dimensions.