Changes in lipid composition during dry grind ethanol processing of corn

During the dry grind ethanol process, ground corn is fermented and the major co-product is a feed called distillers dried grains with solubles (DDGS). This study investigated the changes that occur in the composition of corn oil that can be extracted from various process fractions during the dry grind ethanol process. In the first part of this study, samples of distillers dried grains, thin stillage, condensed distillers solubles (also known as syrup), and DDGS were obtained from 7 dry grind ethanol plants. The levels of deleterious free fatty acids were high (>7%) and those of valuable total phytosterols were also high in all fractions (>2%). In the second part of this study, changes in the content and composition of the fatty acids, phytosterols, tocopherols and tocotrienols were quantitatively analyzed in crude oil samples extracted from nine dry grind process fractions from three commercial ethanol plants. Fatty acid and phytosterol composition remained nearly constant in all nine fractions, although some significant variations in phytosterol composition existed among the fractions. Examination of the tocopherols and tocotrienols revealed that γ-tocopherol was the most abundant tocol in ground corn but an unknown tocol became the predominant tocol after fermentation and persisted in the remaining processing fractions and in the final DDGS product. Overall, the remaining majority of tocols remained relatively unchanged.