Effect of planting date on maize starch structure, properties, and ethanol production

Two maize lines grown in Iowa with planting dates between early to mid-April and late May to June in 2008 and 2009 were used to examine how planting date of maize affects kernel characteristics. Planting the maize lines in late May and June (after optimum planting period) resulted in smaller granular-sizes and amylose contents of starch for both lines but larger proportions of short amylopectin branch-chains for the 37Y14 maize and no change to the length of the B73 amylopectin. Gelatinization and pasting properties did not consistently change with planting dates and their response varied across maize lines and planting years. Enzymatic hydrolysis rates of the starches increased with later planting dates. The ethanol yield calculated on a dry-kernel-mass basis was not significantly affected by maize planting dates, whereas the ethanol yield per unit of maize-planting area decreased with plantings done in late May and June because of reduced grain yield inherent with late plantings.