Effects of A‐ and B‐type starch granules on composition, structural, thermal, morphological, and pasting properties of starches from diverse wheat varieties

The distribution of A‐ and B‐type‐sized starch granules plays a deciding role in controlling the physicochemical, structural, morphological, and functional attributes of wheat starch. Starches of three Indian wheat varieties, viz. DBW 16, WH 147, and WH 542, were fractionated into A‐ and B‐type starch granules and further evaluated for their influence on various attributes of wheat starches using different analytical tools like X‐ray diffraction, scanning electron microscopy (SEM), differential scanning calorimetry, and rapid viscoanalyzer. SEM revealed that the size of large granules (A‐type) ranged from 12.6 to 36.4 µm and small granules (B‐type) varied from 2.53 to 7.52 µm. The amylose content was significantly higher for A‐type starch ranging from 26.6% to 29.68% than B‐type starch ranging from 19.20% to 22.38%. The highest swelling power was observed for B‐type granules, followed by native and A‐type granules, and similar trend was noticed for water absorption. Pasting viscosities of A‐type granules were higher than B‐type for starches of all wheat varieties. A higher pasting temperature was observed in B‐type starch granules, suggesting more resistance to swell during the heating process. X‐ray diffraction of wheat starches showed A‐type pattern of crystallinity, variety DBW 16 (27%) showed the highest relative crystallinity and intensities of peaks in comparison to varieties WH 147 (23.5%) and WH 542 (22.4% as observed in diffractograms and well supported by Fourier transforms infrared spectroscopy. Fractionated large granules of wheat starches exhibited a higher gelatinization temperature than smaller granules and native starches for all the varieties. It was also observed that A‐type granules had higher onset temperature comparatively, which suggested that high energy is required in gelatinization due to more ordered arrangement of starch molecules.