Changes in Corn Protein Content During Storage and Their Relationship with Dry Grind Ethanol Production

Changes in corn grain during storage can cause variations in dry grind ethanol yields. The first objective of this study was to determine the effects of postharvest storage on dry grind ethanol concentrations. Ethanol concentrations for corn stored under ambient and refrigerated conditions were measured every 4 weeks for 1 year. Ethanol concentrations had a decreasing trend for corn stored from 0 to 16 weeks and an increasing trend from week 16 to 24. These trends were similar for corn stored at refrigerated and ambient conditions. The effects of postharvest storage on soluble protein content and their relationship with ethanol concentration were also evaluated. Stored corn was sampled at weeks 0, 8, 16, 24, and 40. Soluble proteins were extracted using a sequential extraction procedure and expressed with respect to the total crude protein of corn, and the total values were not affected by storage temperature (ranging from −7 to 23°C). During 8 to 40 week storage at ambient and refrigerated temperature, the albumin content of corn decreased by 43.6% and 48.5% while the prolamin content increased by 37.9% and 43.0%, respectively. Ethanol yield at 72 hours of fermentation had no correlation with soluble protein content; however, ethanol yield at 24 hours correlated negatively with glutelin (r = −0.76) and positively with prolamin (r = +0.74) contents.