Effect of condensed tannins from sorghum (Sorghum Bicolor (L.) Moench) on in vitro starch digestibility and α-amylase activity

(Sorghum Bicolor (L.) Moench) on in vitro starch digestibility and α-amylase activity Authors: N.L. Mkandawire, R.C. Kaufman, S.R. Bean, C.L. Weller, D.S. Jackson, D.J. Rose Submitted to: Journal of Agricultural & Food Chemistry Recently, the effects of sorghum tannins on starch digestibility in humans have been of interest, since tanins may inhibit starch digestion and contribute to reducing glycemic index and increasing resistant starch. Sorghum tannins could inhibit starch digestion by binding to starch or by inactivating starch degrading enzymes. Tannin containing sorghum lines have been reported to vary widely not only in tannin content, but also in molecular weight and antioxidant activity. Thus, the objectives of this study were 1) to determine the effect of tannins on starch digestion and 2) to investigate the mode, if present, in which tannins inhibit digestion of cooked starches. Significant variability was seen in the impact on starch digestibility in cooked sorghum samples from a diverse set of tannin-containing sorghum varieties. Data collected in this study indicate that sorghum tannins reduce starch digestibility by binding starch digestive enzymes rather than starch. The degree of amylase inhibition depended on tannin molecular weight, with high molecular weight tannins having greater inhibitory activity. This research points out the importance of considering tannin chemistry in addition to simply tannin content when developing sorghum lines with improved human health characteristics. Contact Scott Bean, telephone 785-776-2725, email [email protected]