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ARS Home » Plains Area » Manhattan, Kansas » Center for Grain and Animal Health Research » Grain Quality and Structure Research » Research » Publications at this Location » Publication #309423
Title: Interaction of sorghum tannins with wheat proteins and effects on in vitro starch digestibility in wheat flour tortillas

Author
item DUNN, KRISTEN - Texas A&M University
item YANG, LIYI - Texas A&M University
item GIRARD, AUDREY - Texas A&M University
item Bean, Scott
item AWIKA, JOSEPH - Texas A&M University

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2015
Publication Date: 1/9/2015
Citation: Dunn, K.L., Yang, L., Girard, A., Bean, S., Awika, J. 2015. Interaction of sorghum tannins with wheat proteins and effects on in vitro starch digestibility in wheat flour tortillas. Journal of Agricultural and Food Chemistry. 63(4):1234-1241.

Interpretive Summary: Excess calorie intake and associated disease risks are a major problem in many parts of the world. Carbohydrates contribute the most calories in the diet, making starch-based foods a logical target for improvement. This study investigated the potential interaction of tannins from sorghum bran with proteins and starch during wheat flour tortilla processing, and impact on in vitro starch digestibility. Tortillas made with 25% tannin sorghum bran added had significantly increased amounts of slow digestibility starch and lower levels of rapidly digestible starch than other treatments. Overall, evidence suggests that the sorghum tannins significantly interact with wheat proteins during dough development in ways that may impact starch digestibility in wheat-based products.

Technical Abstract: Excess calorie intake and associated disease risks are a major problem in many parts of the world. Carbohydrates contribute the most calories in the diet, making starch-based foods a logical target for improvement. This study investigated the potential interaction of sorghum bran proanthocyanidins (tannins, PA) with proteins and starch during wheat flour tortilla processing, and impact on in vitro starch digestibility. Refined wheat flour tortillas were substituted at 10, 15, and 25% (baker’s) with brans from wheat and white (low in phenols), brown (high in PA), and black (high in monomeric phenols) sorghum. Dough phenolic profile, starch digestibility, and protein solubility and digestibility were evaluated during tortilla processing and storage. Dough formation drastically decreased extractable phenol content in brown sorghum bran dough (= 58%) compared to non-tannin bran treatments (= 18%). A large decrease in extractability of polymeric PA was responsible for the decrease in phenols in the brown sorghum dough. The PA in brown sorghum bran interacted with proteins during dough mixing to significantly increase insoluble proteins (IP) (460 mg/g protein) compared to other sorghum bran treatments (330 mg/g protein). The brown sorghum bran (at 25% substitution) tortillas had significantly (p < 0.05) higher slow digesting starch and lower rapidly digesting starch than all other bran treatments, suggesting the PA-protein interactions may have slowed starch digestibility. In vitro protein digestibility of the brown sorghum bran tortilla was also the lowest, but not significantly different from the black sorghum bran treatment. Overall, evidence suggests that the sorghum PA significantly interact with wheat proteins during dough development in ways that may impact starch digestibility in wheat-based products.