Gelatinization Characteristics of Starch from du,wx, ae,and ae wx Endosperm of Sweet Corn Inbred la5125

Starch gelatinization in excess water was studied by differential scanning calorimetry for the mutants dull (du), waxy (wx), and amylose extender (ae), and the double mutant amylose-extender, waxy (ae wx) from the Ia5125 sweet corn inbred background. Onset temperature (T_o), peak temperature (T_max), and enthalpy (ΔH) were determined. For du and wx starches T_max was within 1°C of the value for the normal starch (T_max = 69.4°C). For starches from ae and ae wx mutants, T_max was 7–8°C higher than the normal starch. The highest enthalpies were observed for wx (3.26 cal/g) and ae wx (3.39 cal/g) starches; ae (2.93 cal/g) and normal (2.52 cal/g) starches were intermediate, and du (2.32 cal/g) starch had the lowest enthalpy. The endotherm of the ae starch was completed at just above 100°C, in distinction to reports for ae mutants from dent lines. Although the ae wx endotherm occurred at a higher temperature than the wx, the endotherm was sharpened relative to the ae endotherm, and was complete at 90°C.