Assessment of the prebiotic properties of fructooligosaccharides extracted from dragon fruit (Selenicereus undatus) peel

Dragon fruit peel contains fructooligosaccharides (FOS), which are fructose polymers considered a relevant source of soluble dietary fiber with potential prebiotic effects since they are selectively fermented by the intestinal microbiota. The aim of this study was to evaluate the extraction and partial purification of FOS present in dragon fruit peel. Resistance to hydrolysis was analyzed in a static in vitro digestion model, and the effect of the extract as a carbon source substitute to stimulate the growth of three bacterial strains: Lacticaseibacillus casei, Lacticaseibacillus rhamnosus, and Lactobacillus delbrueckii. FOS were extracted following a 2² factorial design with four central points to assess the effect of peel/solvent ratio (A) and solvent ratio (B) on the extraction of fructooligosaccharides from freeze-dried dragon fruit peel flour. After extraction, an ultrafiltration process was carried out using a membrane with a cutoff size of 1 kDa. Data analysis determined that the best treatment was the solid/solvent ratio of 1:30 (w/v) with ethanol at a concentration of 40%. A hydrolysis resistance of 56.36% was observed. The ultrafiltered extract significantly (p < 0.05) stimulated the growth of the L. casei strain, while the non-ultrafiltered extract more effectively promoted the growth of L. rhamnosus; in the case of L. delbrueckii, neither extract significantly (p < 0.05) stimulated its growth. This study demonstrated that fructooligosaccharides extracted from dragon fruit peel have partial resistance to hydrolysis and can stimulate the growth of L. casei and L. rhamnosus strains.