Comparison of in vitro starch digestibility and structure of matcha-fortified starch vermicelli from different botanical sources

BACKGROUND To explore the utilization of polyphenols in complex digestive systems, starch-based vermicelli was employed for the carrier and matcha (MT) was used as the source of polyphenols. 4% MT was extruded with A-, B- and C-type starch of rice, sweet potato and mung bean to prepared starch vermicelli (RSV, SPSV and MBSV). The multi-scale structure of starch, the digestive kinetics of starch and bioaccessibility of polyphenols during in vitro digestion were monitored. RESULTS MT did not change the crystal configuration of vermicelli, but increased the molecular order of RSV. Vermicelli with MT possessed a more uniform structure, and the polydispersity index decreased from 3.85 ~ 4.89 to 2.56 ~ 3.69. However, these structural changes had a limited contribution to delay digestion. Detection of polyphenols during digestion revealed that the release of most polyphenols was accomplished in the first 20 min of digestion. The release amount was in the order of RSV + MT > MBSV+MT > SPSV+MT, and reached to 4.81 ~ 5.45 mg GAE/g. Correspondingly, the activity of digestive enzyme decreased in the order of RSV + MT < MBSV+MT < SPSV+MT. Consequently, MT significantly ( p < 0.05 ) reduced digestive rate of vermicelli, and the rapidly digested starch and predicted glycemic index of RSV + MT decreased from 71.28% to 56.31% and from 74.68 to 62.86, respectively. The released polyphenols were also the main source of the strong antioxidant capacity of vermicelli with MT. CONCLUSIONS These results provided a theoretical basis for using polyphenols to pursue healthy starch-based food. This article is protected by copyright. All rights reserved.