Effects of exogenous starch on the structural-thermal properties of gluten in wheat with HMW-GS variations at Glu-D1 locus

Abstract

To further understand the gluten-starch interactions in dough, this study investigated the effects of exogenous starch on the structural-thermal properties of gluten via reconstituting Xinong 836 starch with gluten from near-isogenic lines HMW-D1a (Dy12) and HMW-D1p (Dx2 + Dy12) according to the following proportions (gluten/starch): 9/91 (G09), 12/88 (G12), 15/85 (G15), and two controls, where G00 and G01 represent the original and self-reconstituted flours, respectively. Adding exogenous starch significantly improved the dough strength for the reconstituted flours containing gluten from HMW-D1a and HMW-D1p, especially those with HMW-D1a. When the ratios of gluten to starch were 15/85 and 12/88 in the HMW-D1a and HMW-D1p reconstituted flours, respectively, the concentrations of free sulfhydryl groups were minimized in the flour, and thus more glutenin polymers were formed. Changes in the secondary structure, such as the proportion of β-sheets and the α-helices differed among the gluten types after adding starch. Compared with G00, the microstructures of dough obtained from G15 with HMW-D1a and G12 with HMW-D1p were more compact and denser, respectively; the thermal stability was also improved significantly for G15 with HMW-D1a and G12 with HMW-D1p. The effects of adding starch on the gluten characteristics were greater in HMW-D1a than HMW-D1p, attributing to differences in gluten-starch interactions. These findings indicate that adding exogenous starch was more readily to modify the structural properties of HMW-D1a gluten with inferior subunits, which helps to improve the quality of dough prepared with inferior gluten.

Keywords: Exogenous wheat starch; Free sulfhydryl group; Glutenin macropolymer; Microstructure; Reconstituted flour; Secondary structure; Thermal property.