Examining the Properties of Deoiled vs. Unmodified DDGS

Abstract

Distillers dried grains with solubles (DDGS) are an excellent feed ingredient for ruminant livestock and are used in monogastric rations as well. With the remarkable growth of the US fuel ethanol industry in the past decade, large quantities of distillers grains are now being produced. Flowability of DDGS has become a problem throughout the industry, as it is often restricted by caking and bridging during storage and transportation. As DDGS contains modest levels of corn oil (typically between 3 and 13% db), some studies are being directed at removing the fat from DDGS, to improve the marketability of DDGS by concentrating protein and thus making it more equivalent to other high-protein feeds that are typically used for swine and poultry diets. Additionally, the corn oil in DDGS is a ready source of oil for biodiesel production. This use for DDGS corn oil can increase the revenue of ethanol processing facilities, and help move them toward a greater diversity of biorefining products. Removing oil from DDGS will alter the chemical nature of these coproduct feed materials, and may also affect the physical properties as well. In fact, removal of the fat may improve flowability. The objective of this study was to examine and compare the physical (moisture, compressive modulus, and shear stress) and flow (Carr and Jenike) properties of regular and reduced fat (approximately 2% db) DDGS. The compressive modulus of reduced fat DDGS was higher than unmodified DDGS. On the other hand, the compressibility of reduced fat DDGS was less than regular DDGS. For regular DDGS, the flow function curve shifted towards the shear stress (sc) axis, which indicated slightly worse flowability. Overall, a reduction in the fat content did show some improvement in the flow properties, but many of these differences were not significant. As it appears that fat content is not the main driver for DDGS flowability problems, continued research should be pursued, including an examination of the effects of other chemical constituents, as well as particle morphology.