Date of Award

January 2015

Degree Type


Degree Name

Doctor of Philosophy (PhD)


Agricultural and Biological Engineering

First Advisor

Klein E Ileleji

Committee Member 1

Kevin M Keener

Committee Member 2

Tamilee D.D. Nennich

Committee Member 3

Richard Stroshine


Distillers wet grains with solubles (DWGS) is a co-product of the ethanol production using the dry-grind process. DWG is widely used as a feed and supplemental protein source in North American cattle rations. However due to its short shelf-life, 3-4 days in the summer and 7-10 days in the winter, its use is limited to cattle feeding facilities within close proximity to an ethanol production plant. It is known that the shelf-life of DWGS in the summer diminishes drastically compared to DWGS in the winter. This effect is primarily due to temperature, which drives mold growth in high moisture feedstocks. Therefore, the overall goal of this dissertation research was to increase the shelf-life of wet distillers grains by a factor of three from its current 3-4 days in warm summer conditions and 5-7 days in cold winter conditions. The first objective was to understand and quantify the effect of temperature (10, 20, and 25°C) and condensed distillers solubles (CDS) levels [0, 20, 30g/100g of Distillers Wet Grains (DWG)] on the shelf-life of DWGS under warm and cool aerobic storage conditions. Sample conditions which indicate shelf-life such as moisture, pH, fat acidity (FA), fungal growth and mycotoxin levels were measured in the DWGS samples before and after seven days of storage under three storage temperature levels (10, 20, and 25°C). We found that changes in temperature had the most significant effect on sample conditions (P<0.05). After seven days of storage, moisture content and water activity decreased with increase in temperature. We found fat acidity increased after seven days of storage and pH, fungal growth and mycotoxin levels increased with temperature. It was concluded that after seven days of storage at both warm and cool aerobic storage conditions, desired sensory, chemical, physical and microbiological characters were not retained. DWGS deteriorated less at 10°C than at 20°C and 25°C, likewise we saw less deterioration in 0 (g/100g) CDS than in 20 (g/100g) and 30 (g/100g) CDS. Additionally, deterioration and levels of three mycotoxins (aflatoxin, fumonisin and zearalenone) of DWGS stored under cool and warm conditions for a 7 day period were quantified.