Characterization of gluten proteins in different parts of wheat grain and their effects on the textural quality of steamed bread

Abstract

The gluten proteins distribute heterogeneously in the wheat grain, but the characteristics of gluten protein fractions in different layers of the starchy endosperm and their effects on the textural quality of the Chinese steamed bread have not been well understood. The bran and endosperm of wheat grains from six cultivars were peeled from the outer to the inside layer to obtain five fractions (F1 ∼ F5), whose relative weight of the remaining grain around 80%, 67%, 54%, 41% and 28% of the whole grain weight, respectively. It is found that wet gluten content (WGC) of flour basically decreased from F1 to F5, but the gluten index (GI) did not change obviously. For the dough made from F1 to F5 flours, their developing time (DT), stability time (ST), extension area (EA) and extensibility (E) decreased, but the weakening degree (WD) and resistance to extension/extensibility (R/E) increased. These dough rheological results suggested that the rheological properties of dough mainly depended on the gluten content for a given variety of wheat. Moreover, the hardness and chewiness of steamed bread made from F1 to F5 flours increased, but the cohesiveness and resilience decreased, suggesting that F1 flour is more suitable for manufacturing steamed bread with improved textural quality. These findings are useful for quality improvement of steamed bread by selecting the suitable wheat flour fraction.