The Influence of Different Polyphenols on the Digestibility of Various Kinds of Starch and the Value of the Estimated Glycemic Index

Considering the prevalence of diet-related diseases, new ways of preventing them are being sought. One of them is the addition of polyphenols to high-starch products to inhibit their digestibility and reduce their glycemic index. Therefore, this study aimed to investigate the differences between polyphenols popular in food ((+)catechin, epigallocatechin gallate, quercetin, kaempferol, naringenin, hesperidin, trans-ferulic acid, and p-coumaric acid), in terms of their impact on wheat, rice, potato, and maize starch digestibility. Polyphenols were added to starch separately, before and after its pasting, in one of the following doses: 5, 10, and 20 mg. Starch was digested in the presence of single polyphenols to measure RDS (rapidly digestible starch), SDS (slowly digestible starch), RS (resistant starch), and TS (total starch) content. On that basis, the SDI (starch digestion index) was calculated, and the GI (glycemic index) was estimated. The results show that polyphenols inhibit starch digestion at different levels depending on the type of tested starch and the time of polyphenol addition. However, in terms of RDS, TS, and eGI (estimated glycemic index), the greatest impact was observed for epigallocatechin gallate in a dose of 20 mg most frequently, independently of the kind of tested starch and the time of polyphenol addition.