Effect of proanthocyanidin MW profile on dough rheology
A. GIRARD (1), J. Awika (1), E. Castell-Perez (1) (1) Texas A&M University, College Station, TX, U.S.A..

Proanthocyanidins (PA) strongly complex with proteins and may be exploited to naturally expand gluten functionality. This study investigated the effect of PA with different MW profiles (from sorghum & grape seed) compared to monomeric catechin, on wheat gluten properties. Two gluten profiles were used: a bread wheat with a high ratio of high molecular weight glutenin subunits (HMW-GS) (SG) & a deletion line with reduced HMW-GS content (WG). PA were added at 0.8-2.5 mg/g flour or purified gluten. PA, dough, & gluten profiles were analyzed by HPLC & rheological methods. Sorghum PA was more (91%) polymeric than grape PA (42%). Mixograms & extensibility data showed catechin significantly (p<0.05) weakened dough, as expected of an antioxidant. However, grape & sorghum PA strengthened dough by increasing mixing tolerance, peak time, & force to extend dough. Sorghum PA had a greater strengthening effect. Retarded compliance (J1) in WG decreased from 3.5 (control) to 3.0 & 1.9 KPa-1 with grape & sorghum PA, respectively (at 2.5 mg/g flour). This indicates sorghum PA produced a stiffer structure. Catechin increased deformation to 4.1 KPa-1. Similar but less differentiated trends were seen in SG. Sorghum PA also reduced deformation vs control for WG (4.5 vs 14.4 KPa-1, respectively) & SG (1.0 vs 2.8 KPa-1, respectively) in purified glutens. Size-exclusion chromatography on SG showed sorghum PA increased insoluble polymeric protein (IPP) significantly vs other treatments & control (12.3 vs 8.2-8.4 AU, respectively). In WG, both sorghum & grape PA increased IPP (9.1 & 7.5 AU, respectively) compared to catechin (4.1) & control (4.3). The evidence suggests higher MW sorghum PA, crosslinked gluten more effectively than grape seed PA. Additional work is investigating the nature of the interactions. Sorghum PA is a promising natural ingredient to improve & expand gluten functionality.

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