Characterization of normal and waxy corn starch for bioethanol production.

Objectives of this study were to compare ethanol production between normal and waxy corn using a cold fermentation process and to understand effects of starch structures and properties on ethanol production. Ethanol yields positively correlated (p < 0.01) with starch contents of kernels of the normal and waxy corn. The average starch-ethanol conversion efficiency of waxy corn (93.0%) was substantially greater than that of normal corn (88.2%). Waxy corn starch consisted of very little amylose and mostly amylopectin that had a shorter average branch chain length than normal corn amylopectin. Regression analyses showed that average amylopectin branch chain lengths and percentage of long branch chains (DP > 37) of waxy corn starch negatively correlated with the starch hydrolysis rate and the ethanol yield. These results indicated that starch structures and properties of the normal and waxy corn had significant effects on the ethanol yield using a cold fermentation process.