Maize Proximate Composition and Physical Properties Correlations to Dry-Grind Ethanol Concentrations

Dry-grind ethanol plants incur economic losses because of seasonal variations in ethanol yields. One possible cause associated with ethanol yield variability is incoming grain quality. There is little published information on factors causing variation in dry-grind ethanol concentrations. The objective of this study was to determine relationships between rapidly measurable corn quality attributes (physical parameters and chemical composition) and dry-grind ethanol concentrations. Corn samples obtained from a Midwestern ethanol plant were analyzed for physical quality parameters (test weight, kernel weight, true density, percent stress cracks, and moisture content) and composition (starch, protein, oil, and soluble sugars contents) and then processed with a laboratory-scale dry-grind procedure. There were significant (P < 0.05) variations in corn quality parameters and ethanol concentrations. Correlation coefficients were significant (P < 0.05) but low (-0.50 < r < 0.50) between starch content and final ethanol concentrations (72 h) and total soluble sugar content and ethanol concentrations at 72 and 48 h. Ethanol concentrations (at 24, 48, and 72 h) were predicted as a function of a combination of grain quality factors using multiple regression methods; however, the R-2 values obtained were low. Variations in ethanol concentrations were not related to physical and chemical composition quality factors. Other factors, such as structural and physiologic attributes of corn grain, need to be evaluated.