In vitro bioaccessibility and bioavailability of quercetin from the quercetin-fortified bread products with reduced glycemic potential

Quercetin, a plant-extracted flavonol, is a potent inhibitor of carbohydrate digestive enzymes. This study aimed to examine: (1) the extent to which quercetin altered the starch digestion and the glycemic potential of the fortified western baked bread as well as oriental steamed bread, (2) the matrix effects of bread on the potential bioaccessibility and bioavailability of quercetin. The starch digestion of bread was quantitatively evaluated by determination of starch digestion rate (k) via a developed mathematical model. Results showed a significant reduction of k for the 1.5, 3, and 6% quercetin-fortified baked and steamed bread compared to the controls by up to 18.3%. The predicted GIs of the baked bread samples with quercetin were significantly reduced in comparison to control bread. Moreover, the potential bioaccessibility of quercetin incorporated in bread products was significantly higher than that of quercetin supplement probably as a result of the protective effects from food matrix.