Physicochemical, thermal and rheological properties of commercial wheat flours and corresponding starches

The quality attributes, including physicochemical, thermal and theological properties of commercial bread, pau, multipurpose and cake flours, as well as their corresponding isolated starches were analyzed. Bread flour showed the highest solvent retention capacity (SRC) and gluten performance index (GPI), suggesting better functionality than others. Starch was isolated from all types of flour and fractionated into A-type and B-type starch granules. A-type disk-like starch granule had larger diameter (>10 mu m) than B-type spherical starch granule (<5 mu m diameter). For bread, pau and multipurpose flours, A-type starch granules contained higher amylose content than B-type and unfractionated starch granules significantly. Results suggested a high degree of crystallinity and high amount of amylose-lipid complexes in A-type starch granules, thus leading to low swelling power, solubility, gelatinization onset (T-o) and peak (T-p) temperatures. However, cake flour showed contrary properties, where B-type starch granules consisted higher amylose content than A-type starch granules. Furthermore, A-type and unfractionated starch granules of all types of wheat flour exhibited shear thickening behavior at 25-45 degrees C, but shear thinning behavior at 65 degrees C. The outcomes would be of benefit to the quality improvement on wheat flour with particular functionalities of their starches for specific applications.