Swelling Characteristics of Native and Chemically Modified Wheat Starches as a Function of Heating Temperature and Time

Abstract The effects of hydroxypropylation (molar substitution, MS 0.05, 0.12, and 0.18) and cross‐linking (0.03%, 0.1%, and 0.2%) on swelling properties of wheat starch granules at several temperatures and heating times were investigated by laser diffraction particle size analysis. Starch samples were dispersed in water at temperatures ranging from 30 to 90°C, for 1 to 360 min. All starch granules exhibited distinct bimodal size distributions: small B‐granules with mean diameter of 2.3 μm and large A‐granules with mean diameter of 20.4 μm. As temperature increased, the B‐granules swelled more than A‐granules. Swelling of A‐granules sharply increased at 60°C. Swelling was more pronounced with increasing molar substitution of hydroxypropyl groups, while increased swelling was not observed in cross‐linked starches. The dependence of swelling capacity on heating time was different at 60 and 80°C as well as amongst modified starches. As heating time was prolonged, mean granule sizes for native, control, and hydroxypropylated starches at 80°C decreased after reaching maximum size due to loss of granule integrity, while those at 60°C showed no significant change.