Interaction of Sorghum Tannins with Wheat Proteins and Effect on in Vitro Starch and Protein Digestibility in a Baked Product Matrix

Abstract

Carbohydrates contribute the most dietary calories, which makes starchy foods a logical target for modifying calorie intake. This study investigated the interaction of sorghum bran proanthocyanidins (PA) with proteins during wheat flour tortilla processing and impact on in vitro starch digestibility. Brans from wheat, white (low in phenols), brown (high PA), and black (high monomeric flavonoids) sorghum were used. Changes in phenolic profile, starch, and proteins were evaluated. Dough mixing drastically decreased extractable PA (61-72%) but not monomeric phenolics; higher MW PA decreased the most. The high PA bran dough produced the highest insoluble proteins (460 vs 330 mg/g protein for other sorghum brans) at 25% baker's substitution. The high PA bran tortillas also had higher slow digesting starch and lower rapidly digesting starch than all other bran treatments. Significant sorghum PA-gluten interactions occur during dough mixing that may slow starch digestibility in the baked products.