Raisins ( Vitis vinifera L.) as a Source of Prebiotic Functional Food

In the present work we report the potential prebiotic effect of sun‐dried raisins, known to be a source of fructo‐oligosaccharides (FOS). A full model of gastrointestinal tract digestion, including gastric and small intestinal environments and a colonic model of in vitro fermentation with representative human gut bacteria was used. Bacterial identification was performed by plate counting on selective media and 16S V4 rDNA analysis. Results from plate counting showed an increase in the numbers of beneficial bacteria, such as bifidobacteria and lactobacilli, after fermentation with raisins. Higher prebiotic index (PI) scores were recorded after 8 and 24 h fermentation with raisins compared with negative control (no carbon source added). Microbial profiling showed a bacterial abundance shift in the whole microbiome, with an increase of Bifidobacteria after fermentation with raisins and FOS, used as positive control. This trend was stronger with Bifidobacterium sp . than Lactobacillus sp . The concentration of lactic and acetic acids increased after fermentation with raisins (11.6 and 36.5 mmol/l after 24h, respectively), demonstrating a beneficial effect correlated to the increase in the number of beneficial bacteria. In conclusion, we have shown that bioactive components in raisins were able to modulate the growth of gut bacteria. Sun‐dried raisins exhibited the potential to be used as a novel source of prebiotics.