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Effect of Moisture Content and Soluble Level on the Physical, Chemical, and Flow Properties of Distillers Dried Grains with Solubles (DDGS)

¹Graduate research assistant, Department of Agricultural and Biosystems Engineering, South Dakota State University, Brookings, SD. ²Professor, Department of Agricultural and Biosystems Engineering, South Dakota State University, Brookings, SD. ³Agricultural and Bioprocess Engineer, USDA-ARS, North Central Agricultural Research Laboratory, Brookings, SD. Mention of a trade name, propriety product or specific equipment does not constitute a guarantee or warranty by the United States Department of Agriculture and does not imply approval of a product to the exclusion of others that may be suitable. ⁴Corresponding author. Phone: 604-693-3241. Fax: 605-693-5240. E-mail address: kurt.rosentrater@ars.usda.gov

Distillers dried grains with solubles (DDGS) is a bulk material that has been widely used as a protein source for ruminants and nonruminants for more than two decades. DDGS is the nonfermentable processing residue (i.e., protein, fiber, fat, and ash) from fuel ethanol manufacturing. With the exponential growth of the fuel ethanol industry in the past several years, significant quantities (≈13.0 million tons in 2007) of distillers grains are now being produced. To effectively utilize these coproduct streams in the domestic market, DDGS must be transported greater distances and must be stored until final use. DDGS flow is often problematic as it can become restricted by caking and bridging that occur during shipping and storage. This flowability problem can present itself during dynamic and static flow conditions. This issue most likely results from physical or chemical interactions between particles (including particle size and shape), storage moisture, temperature, and relative humidity variations, as well as storage time. The objective of this study was to examine the effect of five moisture content levels (10, 15, 20, 25, and 30% db) on the resulting physical and chemical properties of DDGS with four soluble levels (10, 15, 20, and 25% db). To produce these materials, condensed distillers solubles (CDS) were combined with DDG, and appropriate quantities of water were added to adjust moisture contents. Carr indices were used to quantify the flowability of the DDGS samples. The results showed that both soluble level and moisture content had noticeable effects on physical and flow properties (e.g., aerated bulk density, packed bulk density, and compressibility). According to dispersibility, flowability index, and floodability index, flowability generally declined significantly (P < 0.05) with an increase in moisture content for most of the soluble levels under consideration. The color values and protein content of the DDGS were significantly affected (P < 0.05) as soluble level increased as well.