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ARS Home » Plains Area » Brookings, South Dakota » Integrated Cropping Systems Research » Research » Publications at this Location » Publication #216367

Title: PHYSICAL AND FLOW PROPERTIES OF REGULAR AND REDUCED FAT DDGS

Author
item GANESAN, V
item Rosentrater, Kurt
item MUTHUKUMARAPPAN, K

Submitted to: Food and Bioprocess Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2007
Publication Date: 11/29/2007
Citation: Ganesan, V., Rosentrater, K.A., Muthukumarappan, K. 2007. Physical and flow properties of regular and reduced fat ddgs. Food and Bioprocess Technology. Available: www.springerlink.com/content/c00198n11613t804/.

Interpretive Summary: 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 ('c) 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.

Technical Abstract: With the remarkable growth of the US fuel ethanol industry in the past decade, large quantities of corn-based distillers dried grains with solubles (DDGS) 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 transport. The objective of this study was to quantify physical and flow properties of commercially-produced unmodified (9.3% db fat) and reduced fat (2.1% db) DDGS, to determine if fat level affects flowability. The compressive modulus of reduced fat DDGS was 28.2% higher than unmodified DDGS, but shear stress resistance was the same (0.03 kg/m2). Carr testing indicated that reduced fat DDGS had an angle of repose 4.3% lower, and Carr compressibility 70% lower, than unmodified DDGS. But, in terms of uniformity and dispersibility, reduced fat DDGS was, respectively, 100 and 41.5% greater than regular DDGS. Jenike shear testing revealed that reduced fat DDGS had unconfined yield strength and Jenike compressibility values that were 15.7 and 40.0% lower, respectively, than unmodified DDGS, but had major consolidating stress and flowability index values that were 6.7 and 13.2% higher, respectively. For regular DDGS, the flow function curve was located closer to the shear stress axis, which indicated slightly worse flowability than the reduced fat DDGS. Overall, a reduction in the fat content did show slight improvement in some flow properties, but not in others. And both types of DDGS were ultimately classified as cohesive in nature. As it appears that fat content may not be 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.