Process and Engineering Effects on Ddgs Products – Present and Future

In a conventional dry grind process, corn is processed to produce ethanol and a low valued animal food coproduct called distillers dried grains with solubles (DDGS). Approximately 33% of corn in dry grind ethanol plant becomes DDGS. Due to its high fiber content DDGS has traditionally being sold as ruminant foodstuffs. New fractionation technologies are being implemented to recovery valuable coproducts, reduce amount of DDGS produced and improve fermentation efficiency in conventional dry grind ethanol plants. These technologies include corn fractionation as well as DDGS fractionation. Corn fractionation can be broadly classified as wet and dry technologies. Wet fractionation involves a short soaking of corn followed by milling to recover germ, pericarp fiber and/or endosperm fiber in an aqueous medium prior to fermentation of degermed defibered slurry. In dry fractionation, a dry degerm defiber process is used to separate germ and pericarp fiber prior to fermentation of the endosperm fraction. Both wet and dry processes reduce the total amount of DDGS produced, increase it protein content and reduce its fiber content. Depending upon the modified process used, the amount of DDGS produced can be reduced by 70% and its protein content can be increased to 58%. DDGS fractionation involves sieving and elutriation (aspiration) to separate fiber from DDGS. This process recovers fiber as a coproduct, increases protein and fat content of residual DDGS and reduces the fiber content of residual DDGS. Depending upon the parameters used this process increased protein and fat contents of residual DDGS from 28 to 41% and 12 to 14%, respectively. A reduction in fiber content and increase in protein content of DDGS could allow increased use of DDGS as nonruminant foodstuffs.