Impact of Starch Properties on Hearth Bread Characteristics. II. Purified A- and B-granule Fractions

Summary

Starch and A- and B-granule fractions were purified from 6 different bread wheat flours with similar protein content. For each starch fraction the starch granular size distribution, gelatinisation, pasting, and gelation properties were measured. In addition the chain length of amylopectin was obtained. The results from the analyses of flour and purified starch fractions were related to the properties of the bread loaves by multivariate statistical methods. A-granule fraction have the highest gelatinisation enthalpy, lowest gelatinisation onset and peak temperature. B-granule fraction had the highest amylose/lipid complex enthalpy and the lowest onset temperature. A-granule fraction has the highest peak viscosity, minimum viscosity, breakdown viscosity, final viscosity and setback viscosity. The models obtained use A-granule fraction thermal and pasting properties. DSC measurements and pasting properties measured with RVA explained 81% and 69% respectively of the total variance in hearth bread baking data for weight. No model was obtained for hearth bread characteristic loaf volume and form ratio. To obtain a hearth bread with a high weight the flour must contain A-granules with high level on DSC-parameters AT(0), AT(a0) and AT(ap) and low levels on ADeltaH1, ADeltaH2 and AT(p). In addition A-granules must have the following levels on RVA parameters: low breakdown and a low pasting temp. and a high final viscosity.