Gelatinization of Starches From Corn (Zea mays L.) and Sorghum (Sorghum bicolor (L.) Moench): Effects of Genetic and Environmental Factors1

Abstract

The gelatinization temperatures of starches from 85 samples of sorghum grain of diverse origin and type were determined by a standard microscopic procedure. In general, waxy starches had higher gelatinization temperatures than regular starches. The sweet, juicy stalk characteristic of forage sorghums seemed to depress gelatinization temperature of both waxy and regular starch types.Two commercial grain sorghums and two commercial waxy grain sorghums were grown in each of three locations in the warm, humid Coastal Bend region of South Texas and at a single location in the cooler and less humid High Plains of North Texas. Starch synthesized by plants grown in North Texas consistently gelatinized at a lower temperature (average, 4 C) than starch from the same variety grown in South Texas. Gelatinization end‐point temperatures of the waxy starches were 2 to 3 C higher than those of the regular starches.A 6‐year breeding program to transfer the property of low starch gelatinization temperature from the forage varieties ‘Atlas’ and ‘Hoti’ to acceptable grain types was unsuccessful. Waxy derivatives from this program had a higher starch gelatinization temperature than derivatives with regular starch.Two commercial maize hybrids and their waxy counterparts were grown in central Illinois. In each case the waxy starch had a gelatinization temperature higher than that of the regular starch counterpart. Waxy starch from another corn hybrid had a 3 C higher gelatinization temperature when the grain was produced in Texas than when it was grown in central Illinois.