Spatial Distribution Patterns of Protein Components and Quality Traits of Flours from Different Pearling Fractions of Wheat Grains As Affected By Nitrogen Topdressing Timing.

Wheat is one of the crucial source of food in the world, contributing to over 45% of the global food supply (kcal capita-1 day-1) and over 40% of the global protein supply (g capita-1 day-1) over the past decade. It has been known that the content of nutritional material differs in different pearling fractions of wheat grains. However, little attention has been done on the gluten distribution, the quality of bread made by different pearling fractions as well as effects of nitrogen topdressing stage on spatial distribution of gluten proteins. In this study, the effect of nitrogen topdressing stage on protein quality of two wheat cultivars was compared, finding the content of protein and its components, glutenin macropolymer(GMP), high molecular weight glutenin subunits (HMW-GS) and low molecular weight glutenin subunits (LMW-GS) as well as gluten increased with backward nitrogen topdressing stage. Spatial distribution of gluten protein were then evaluated by abrading grain into nine fractions (P1 to P9 from outer to inner). The content of gliadin, glutenin and gluten presented unimodel curve peaking at P2 or P3. Content of gluten protein and gluten in each fractions, especially for aleurone layer and outer endosperm when delaying nitrogen topdressing time. Furthermore, TE1 increased volume, sensory score as well as TPA indexes of bread made by each fraction significantly and bread made by P3 and P4 showed best baking quality comparing with other fractions. The differences of gluten protein distribution in spatial resulting in unique processing quality of different fractions provide a novel view to improve the quality of bread by adding wholemeal from differential positions of grains.