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Submitted to: CRC Press
Publication Type: Book / Chapter Publication Acceptance Date: 1/15/2011 Publication Date: 7/25/2011 Citation: Liu, K. 2011. Chemical Composition of DDGS. Ch.8, in "Distillers Grains: Production, Properties, and Utilization", Liu, K.S., and Rosentrater, K.A. Eds., pp 143-178, CRC Press, Baca Raton, FL Interpretive Summary: Dry grind method represents the majority of fuel ethanol processing in the U.S., and all newly constructed ethanol plants employ some variation on the basic dry-grind process because such plants can be built at a smaller scale for a smaller investment. Although DDGS has been in the market for a century, its surge in global supply in recent years has stimulated many new investigations into this important coproduct of biofuel production. In particular, chemical composition of DDGS has been a great interest to researchers in animal science, ethanol producers, and traders in feed industry. This chapter (Chapter 8) focuses on major and minor nutrients in DDGS in terms of concentrations (quantity), composition (quality), changes during the entire dry grind process, and the underlying causes for high compositional variation of DDGS. Additional topics, including particle size of DDGS, its relationship with chemical composition, and wet fractionation of DDGS, are also discussed. It is hoped that information provided in this chapter will help us better understand the dry-grind process, and develop strategies to control the compositional variation in DDGS. This chapter is an integral part of the book, Distillers Grains: Production, Properties and Utilization, (2011, by CRC Press, Baca Raton, FL), which brings together cutting edge information on many aspects of DDGS. More information can be found at the publisher’s website: http://www.crcpress.com/product/isbn/9781439817254 Technical Abstract: 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. Higher fold of increase in S, Na, and Ca, are mostly due to exogenous addition during processing, while unusual change in inorganic phosphorus (P) and phytate P indicates phytate hydrolysis by yeast phytase. Fermentation causes major changes, but other processing steps are also responsible. Although DDGS is nutritious as a livestock feed ingredient, or even for aquafeed and pet food, one key challenge for using DDGS as a feed ingredient is its large variation in nutrient levels as compared to some other feed ingredients, such as soy meal. The causes for varying DDGS composition are multiple, including differences in feedstock species and composition, process methods and parameters, the amount of condensed solubles added to distiller wet grains, the effect of fermentation yeast, and analytical methodology. Most of them can be attributed to complexity of the dry-grind process itself. For better utilization of DDGS, both suppliers and end users need better understand factors that cause variation and develop strategies to decrease it. |
