Compositional changes during grain-based fuel ethanol production and method modifications to recover co-products for human or pet food utilization

Authors: Liu, Keshun

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 4/26/2012
Publication Date: 6/25/2012
Citation: Liu, K.S. 2012. Compositional changes during grain-based fuel ethanol production and method modifications to recover co-products for human or pet food utilization. A symposium presentation for the Institute of Food Technologists Annual Meeting & Expo, Las Vegas, NV, June 25-28.

Interpretive Summary:

Technical Abstract: The surge in global supply of distillers dried grains with solubles (DDGS) in recent years has stimulated many new investigations into this important co-product of grain-based fuel ethanol production. Compositional changes during the entire dry grind process has been one of them, since DDGS is characterized by high variation in composition and high levels of phosphorus (P), sulfur (S) and some other minerals. These characteristics have limited DDGS uses as a value added ingredient. During processing, starch is converted to glucose and then to ethanol and carbon dioxide. Most other components are relatively unchanged but concentrated in DDGS about 3-fold over the original feedstock. However, there are also higher fold of increases in S, Na, and Ca concentrations as well as unusual changes in inorganic phosphorus (P) and phytate P. Fermentation causes major changes, but other processing steps are also responsible. The uncontrollable amount of condensed solubles added to distiller wet grains during the drying step has been identified as a key cause for varying DDGS composition. To improve recovery and composition of co-products, several modified dry-grind methods have been developed over the years, featured by a fractionation either before or after fermentation. At USDA-ARS, we have developed a novel method to recover co-products from the dry-grind process. The new method not only produces distiller grains with much less variable composition but also generates new co-products with unique composition. These include a modified solubles product that has increased protein and reduced fat and ash contents, and a fraction rich in ash (around 30%). The two new co-products can be used as a protein ingredient and mineral supplement in human or pet food, respectively.