Effects of tea polyphenols and gluten addition on in vitro wheat starch digestion properties

Starch-containing food normally has complex components and structure, which control its digestion kinetic properties and nutritional value. However, interactions among multiple food components and their effects on starch digestion kinetics are rarely reported. Here, we evaluated the influence of tea polyphenols [i.e., (-)-epigallocatechin (EGC) and (-)‑epigallocatechin‑3‑gallate (EGCG)] on the in vitro digestion rate and extent of wheat starch in the presence of gluten under uncooked and cooked conditions. The addition of EGC (20%, starch basis) did not change the starch digestion rate and extent for both uncooked and cooked physical forms in the presence and absence of gluten, whereas EGCG (20%, starch basis) significantly reduced the digestion extent of wheat starch by 25-30% in the absence of gluten and by 6.6-18.5% in the presence of gluten, a phenomenon that was caused by the reduced effective EGCG due to its interaction with gluten.