Thermal, pasting and morphological properties of starch granules of wheat (Triticum aestivum L.) varieties

Large (A) and small (B) granules of wheat starch were separated and their morphological, thermal, structural and pasting properties were investigated. The pasting properties of starches from two wheat varieties showed significant differences. For wheat variety C-306, the unfractionated starch showed higher peak, trough, breakdown, final, and setback viscosities than the starch isolated from wheat variety WH-147. On the contrary, unfractionated starch of variety WH-147 has higher pasting temperature than the starch of the variety C-306. Differential scanning calorimetry results showed that unfractionated starch exhibited the higher gelatinization enthalpy, peak and conclusion temperatures than the isolated A- and B-starch granules from both the varieties. Scanning electron microscopy results revealed that large A-granules appeared to be smooth and displayed disk or lenticular shape having diameter 13-35 mu m, while B-granules showed a spherical shape with diameter of 2-6 mu m. The variations in structures and content would result in starch granules with different chemical and physical properties.