NON-EQUILIBRIUM MELTING OF NATIVE GRANULAR STARCH .1. TEMPERATURE LOCATION OF THE GLASS-TRANSITION ASSOCIATED WITH GELATINIZATION OF A-TYPE CEREAL STARCHES

The temperature location of the effective glass transition (T//g), which immediately precedes the nonequilibrium melting transition of amylopectin microcrystallites and controls the melting process associated with starch gelatinization, was identified for native granular wheat and waxy corn starches, heated at 10 degree C min** minus **1 in the presence of water added to 55% (by weight) total moisture to facilitate temporal resolution of the thermal events. Definitive differential scanning calorimetry experiments, involving partial initial heating scans to intermediate temperatures in the range from 30 to 130 degree C, followed by quench-cooling and immediate complete rescans, revealed the operational location of T//g for wheat starch (above 54 degree C and completed by 63 degree C) and waxy corn starch (above 63 degree C and completed by 71. 5 degree C). Corresponding effective 'end of melting' temperatures (T//m) for nonequilibrium melting transition of amylopectin microcrystallites in normal wheat (about 92 degree C) and waxy corn (about 95 degree C) starches were also identified.