Characterization of some physical and chemical properties of corn distillers wet grains (DWG)

Authors: Rosentrater, Kurt; Lehman, R - Michael

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2007
Publication Date: 2/1/2008
Citation: Rosentrater, K.A., Lehman, R.M. 2008. Characterization of some physical and chemical properties of corn distillers wet grains (DWG). Applied Engineering in Agriculture. 24(1):57-62.

Interpretive Summary: As the ethanol industry in the U.S. grows, so does the quantity of coproducts. These streams are primarily utilized as livestock feed. Distillers Wet Grain (DWG) is one of these coproduct feed materials. Much research has focused on the nutritional properties of DWG, and the response of livestock (primarily beef and dairy) to inclusion in various diets. Physical properties, however, have been largely ignored, but are needed for the proper design of facilities, processes, and applications. The objective of this research was to quantify physical and chemical properties for typical DWG streams. Several properties were determined, including moisture content, water activity, thermal properties, bulk density, color, pH, protein, fiber, fat, and ash. The DWG was golden-brown in color. It had moisture contents ranging between 53 and 54% (wet basis – w.b.), and was highly susceptible to rapid spoilage. It had a very high bulk density (approximately 858 to 975 kg/m3), and had a low propensity for storing and transmitting heat; both of which were due to the high moisture content. Nutritional content of the DWG was similar to that reported by other investigators. Color changes were monitored over time, and it appeared that the Hunter L was correlated with total fungi, yeasts and molds, and aerobic heterotrophs colonizing the DWG. The numerical data generated during this study will help fill the current void, and be useful to the ethanol and livestock industries.

Technical Abstract: The production of corn-based ethanol in the U.S. is dramatically increasing, and consequently so is the quantity of coproduct materials generated from this processing sector. These streams are primarily utilized as livestock feed. Distillers Wet Grain (DWG) is one of these valuable coproduct feeds, and is primary utilized in the locality immediately surrounding an ethanol plant. A fair amount of research has been conducted into determining the nutritional properties of DWG, and the response of livestock (primarily beef and dairy) to inclusion of these feed ingredients. Physical properties, however, have been largely ignored, but are needed for the proper design of storage facilities, processing operations, transportation, and byproduct applications. Thus the objective of this research was to quantify physical and chemical property values for typical DWG streams. Using standard laboratory methods, several properties were determined, including moisture content, water activity, thermal properties (conductivity, resistivity, and diffusivity), bulk density, color, pH, protein, fiber, fat, and ash. The DWG samples in this study were golden-brown in color. They had moisture contents ranging between 53 and 54% (wet basis – w.b.), and were thus highly susceptible to rapid spoilage. They had a very high bulk density (approximately 858 to 975 kg/m3), and had a low propensity for storing and transmitting heat; both of which were due to the high water content. Nutritional content of the DWG studied was similar to that reported by other investigators. Moreover, color changes over time were monitored, and it appears that the Hunter L value can be correlated with total fungi (r=0.60), yeasts and molds (r=0.61), and aerobic heterotrophs (r=0.60) colonizing the DWG. The numerical data generated during this study will help fill the current void, and be useful to the ethanol and livestock industries. But, further study is warranted in order to capture more fully the differences in physical, chemical, and microbial properties between ethanol production plants and over time, and also to develop rapid sensing techniques for the determination of these parameters, and the quantification of spoilage criteria.