Differential Scanning Calorimetry Studies on the Crystallinity of Ageing Wheat Starch Gels

The ageing of wheat starch gels stored at 4°C, 21°C and 30°C was examined by differential scanning calorimetry. Kinetics of the crystallisation process were studied using the Avrami model where it was found that the experimental data fitted the model more satisfactorily when the Avrami exponent was less than unity. At higher storage temperature the starch crystals appeared more symmetrically perfect. Addition of wheat flour pentosans to 50% starch gels did not significantly affect the kinetics of ageing. The extent of crystallisation during the ageing process depends on the moisture content of the starch gel. Crystallinity of the starch gel, measured in the temperature range 306–346°K does not occur if the solids content is below 10% or above 80% and a bell shaped curve is obtained. Reduction of the moisture content of the starch fraction of baked goods either directly or indirectly using materials competing for water, might therefore reduce the staling problem.