Abstract
The relationship between swelling behaviour and thermal transitions of starch was investigated by differential scanning calorimetry (DSC) in combination with swelling power of starch. Sodium dodecyl sulphate (SDS)-treated wheat, waxy maize and potato starches showed increasing swelling power with increasing water/starch ratio. In contrast, swelling power of untreated wheat and high-amylose maize starches increased initially with increasing water/starch ratio, and then remained essentially unchanged above a certain ratio. The main endotherm G of native and SDS-treated wheat starch broadened progressively with increasing water/starch ratio up to 10:1. SDS-treated wheat, waxy maize and potato starches showed a typical endotherm over the whole range of water/starch ratios from 0.33:1 to 25:1, but the maximum enthalpy change occurred at different water/starch ratios. Our results indicate that thermal transition behaviour of starch granules is a very complex process, which involves swelling and leaching of starch polymer molecules rather than the dissociation of double helices or melting of crystallites.
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