The Effects Of Starch Fine Structure On Physicochemical Properties Of Wheat Flour And Quality Of Sugar-snap Cookies

Wheat is one of the major food crops world-wide.The main component of wheat flour is starch,which is mainly composed of amylose and amylopectin.Their fine structures have an important influence on the physicochemical properties(rheological and thermal properties)of wheat flour to some extent,also affecting the eating and processing quality of final products,but the underlying molecular mechanisms are not well understood.In this study,the materials were 16 wheat varieties with different protein content and 16 soft wheat varieties that are suitable for making sugar-snap cookies.Wheat starch molecular chain-length distributions and molecular size distributions were analyzed,and the correlations between structure and property were built,which could explain the effects of starch structures on the physicochemical properties of wheat flour.The main research contents and results are as follows:1.The effects of the chain-length distributions of starch molecules on rheological and thermal properties of wheat flourThe 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 starch,but the mechanisms underlying this are not well understood.In this study,the thermal and rheological properties of wheat flour for 16 wheat varieties were measured and the results fitted with two rheology models.Starch molecular structures were measured by fluorophore-assisted carbohydrate electrophoresis(FACE)and size-exclusion chromatography(SEC).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.The correlation between starch molecular fine structure and rheological and thermal properties of wheat flour was built.We found that long amylopectin chains were positively correlated with onset,peak and conclusion temperatures;the apparent viscosity of wheat flour paste at infinite shear rate was mainly controlled by amylopectin short chains,also viscosity was positively,and elasticity negatively,correlated with the length of them.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.2.Effects of amylose and amylopectin fine structure on sugar-snap cookie dough rheology and cookie qualityStarch,the most abundant component of wheat flour,has a significant influence on sugar-snap cookie quality.but the underlying mechanisms are not understood.In this study,the solvent retention capacity of wheat flour for 16 soft wheat varieties and rheological properties of sugar-snap cookie dough,and cookie physical characteristics and textural properties,were analyzed.Starch molecular structures were measured by size-exclusion chromatography(SEC)and the results parameterized using two biosynthesis-based mathematical models to obtain structure-property correlations.The results show that average molecular size of amylose was significantly and negatively correlated with solvent retention capacity;the viscoelasticity of sugar-snap cookie dough is positively correlated with the length of amylopectin short chains;the length of amylose short chains is positively correlated with cookie thickness and negatively correlated with spread ratio.Starch molecular structure shows no influence on cookie hardness and fracturability.Mechanisms are proposed for these results in detail,which could lead to new ways to improve sugar-snap cookie quality by choosing starches with appropriate structural features.