Retrogradation of du wx and su2 wx maize starches after different gelatinization heat treatments

Retrogradation of du wx and su2 wx starches after different gelatinization heat treatments was studied by differential scanning calorimetry. Suspensions of 30% (w/w) starch were initially heated to final temperatures of 55-180 degrees C. Gelatinized starch was cooled and stored at 4 degrees C. Starch retrogradation in the storage period was influenced by initial heat treatments. Retrogradation of du wx starch was rapid: when initially heated to 80-105 degrees C, retrogradation enthalpy was approximate to 10 J/g after one day at 4 degrees C. The retrogradation enthalpy was approximate to 15 J/g after 22 days of storage, and reached a maximum of 16.2 J/g after 40 days of storage. For du wx starch, application of the Avrami equation to increases in retrogradation enthalpy suggests retrogradation kinetics vary with initial heating temperature. Furthermore, starch retrogradation may not fit simple Avrami theory for initial heating less than or equal to 140 degrees C. Retrogradation of su2 wx starch was slow. After 30 days of storage at 4 degrees C, the maximum retrogradation enthalpy for all initial heating temperatures tested was 7.0 J/g, for the initial heating to 80 degrees C. This work indicates that gelatinization heat treatment in these starches is an important factor in amylopectin retrogradation, and that the effect of initial heat treatment varies according to the genotype.