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Compaction of Corn Distillers Dried Grains¹

¹Contribution of the University of Nebraska Agricultural Research Division, supported in part by funds provided through Hatch Act and Nebraska Research Initiative. ²Industrial Agricultural Products Center, 208 L. W. Chase Hall, University of Nebraska, Lincoln, NE 68583-0730. ³Corresponding author. Phone: 402-472-1634. Fax: 402-472-6338. E-mail address: mhanna1@unl.edu

Corn distillers dried grains (DDGS) were compacted into cylindrical pellets (3.5 cm in length, 1.5 cm in diameter) utilizing a closed-end die under axial stress from a vertical piston applied by an Instron universal testing machine. The effects of independent variables, including the raw material moisture content (25–35% db), processing temperature (100–120°C), pressure (12.5–37.5 MPa), and dwell time (5–15 sec) on pellet density, durability, and stability were determined using response surface methodology. Moisture content, temperature, and pressure significantly affected (P < 0.05) the properties of DDGS pellets, while the influence of dwell time was negligible (P > 0.05). Increasing temperature initially increased and then decreased unit density. High moisture and pressure had favorable effects on unit density and durability rating. The density ratio increased with increasing pressure and moisture content. The results suggested technical feasibility of compacting DDGS. For the range of variables tested, optimum levels were identified as 34.6% moisture content, 107°C press temperature, and 36.8 MPa pressure to obtain maximum durability and density and acceptable dimensional stability.