Solvent retention capacity: Supplemental solvents for evaluation of gluten quality

Solvent retention capacity (SRC) is a solvation test for wheat flour in which functional contributions of different polymeric components are predicted based on their swelling behavior with different diagnostic solvents. To assess the functionality of individual gluten components, four solvents have been proposed: 1) 55% aqueous ethanol for gliadins; 2) 0.75% sodium dodecyl sulfate (SDS) for glutenin macropolymer; 3) 0.006% sodium metabisulfite (MBS) for gluten strength; and 4) 0.75% SDS + 0.006% MBS for glutenin macropolymer without disulfide network. This research aimed to study the gluten functionality of commercial wheat flour samples by the four proposed supplemental diagnostic solvents. Commercial wheat samples were purchased in 2020 at a grocery store in Fargo, North Dakota. Four different brands from three flour types (bread flour, all-purpose flour, and cake flour) were analyzed. These flour types represent wheat flour from three different U.S. wheat classes, hard spring wheat, hard winter wheat, and soft wheat. SRC was measured according to the AACC-approved method 56–11.02 with modifications. The supplementary solvents 55% aqueous ethanol, 0.75% SDS, 0.006% MBS, and 0.75% SDS +0.006% MBS were used instead of the traditional SRC solvents. Highly significant (p ≤ 0.001) and positive correlations between SDS SRC, MBS SRC, and SDS + MBS SRC solvents and the analyzed rheological and baking quality traits, especially water absorption and loaf volume. Additionally, when protein composition was assessed, the three previously mentioned supplementary SRC solvents denoted a significant (p ≤ 0.01) and positive correlation with the glutenin polymers fraction, which is associated with dough functionality. These results highlight the importance of assessing specific flour polymers' functional contributions to predict each flour type's end-use potential.