Physical and Flow Properties of Regular and Reduced Fat Distillers Dried Grains with Solubles (DDGS)

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. However, 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, especially compressibility. Both types of DDGS were ultimately classified as cohesive in nature. Exploration of the data using a previously developed assessment tool appeared to show that the reduced fat DDGS may have better flow. Continued research should be pursued, including an examination of the effects of other chemical constituents, as well as particle morphology.