Synergism and phenolic bioaccessibility during in vitro co-digestion of cooked cowpea with orange juice

Foods are susceptible to matrix interferences during the gastrointestinal transit that can affect bioactive molecules. We proposed in vitro co-digestion of cowpea beans and orange juice to assess polyphenols bioaccessibility and synergisms. We performed gastrointestinal simulation combining beans and a fruit beverage, to mimic a common meal in a more realistic set-up than the usual single-food models. Twenty phenolic compounds were released in oral, gastric and intestinal compartments and were identified by HPLC-DAD. Gallic acid, (-)-epicatechin and chlorogenic acid were the most bioaccessible polyphenols. Cooking and solvent extraction of cowpea beans affected their polyphenolic concentrations. After digestion, the bioaccessibility indexes were higher for cowpea (136.11%) and cooked cowpea (744.74%) when compared to orange juice (31.87%) indicating that the thermal treatment enhanced the bioaccessibility of cowpea phenolics. The antioxidant capacity was higher in the end of co-digestion compared to cooked cowpea and orange juice digested alone due to synergistic polyphenol-polyphenol interactions or polyphenol-protein interactions. The combination of orange juice with cooked cowpea in co-digestion promoted high content of some bioaccessible phenolics, with 10 out of 20 compounds showing positive interactions at the intestinal phase, suggesting that food synergisms are not neglectable for beans and citrus polyphenols release during the digestion course.

Automated summary

This study evaluated the bioaccessibility and synergistic effects of polyphenols in cowpea beans and orange juice through in vitro co-digestion. The results showed that cooking and solvent extraction affected the concentrations of polyphenols in cowpea beans, and thermal treatment enhanced their bioaccessibility. Co-digestion of cowpea beans and orange juice increased the content of bioaccessible phenolics and promoted positive interactions between polyphenols.