The effects of the chain-length distributions of starch molecules on rheological and thermal properties of wheat flour paste

Abstract

The rheological and thermal properties of wheat flour are important for eating and processing quality of flour-based foods. These properties are in part affected by the structure of the component starch, but the mechanisms underlying this are not well understood. In this study, the thermal and rheological properties of wheat-flour paste for 16 wheat varieties were measured and the results fitted with two standard models. Starch molecular structures were measured by fluorophore-assisted carbohydrate electrophoresis and size-exclusion chromatography. The resulting chain-length distributions of amylopectin and amylose were fitted using biosynthesis-based models, thereby representing the data in terms of biologically-meaningful parameters. Protein content was also measured. This gave quantitative relations between starch molecular fine structure and rheological and thermal properties of wheat flour paste. Long amylopectin chains were positively correlated with peak and conclusion temperatures, viscosity was positively, and elasticity negatively, correlated with the length of amylopectin short chains, while protein content showed no significant correlation with rheological and thermal properties. These results indicate that starch fine structure provides additional criteria for the selection of wheat varieties, complementary to the common use of protein composition and amylose content.