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United States Department of Agriculture

Agricultural Research Service

Research Project: SOIL AND CROP MANAGEMENT SYSTEMS FOR IMPROVED NATURAL RESOURCE QUALITY AND EFFICIENCY

Location: North Central Agricultural Research Laboratory

Title: Aerobic stability of distillers’ wet grains as influenced by temperature

Authors
item Lehman, R
item Rosentrater, Kurt

Submitted to: Journal of the Science of Food and Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 13, 2012
Publication Date: August 3, 2012
Citation: Lehman, R.M., Rosentrater, K.A. 2012. Aerobic stability of distillers’ wet grains as influenced by temperature. Journal of the Science of Food and Agriculture. 93:498-503. doi:10.1002/jsfa.5803.

Interpretive Summary: Maximizing the storability of distillers’ wet grains (DWG) has great influence on the economic, energetic, and carbon balances of fuel ethanol production, yet there is little published data from controlled studies on the deterioration of DWG following its production. We evaluated the aerobic stability of wet distillers’ grains by measuring microbial respiration (CO2 production) and mold development over a period of ten days. The evaluation was conducted at three temperatures: 12°C, 22°C, and 32°C. This study was repeated three times with fresh DWG collected from a local fuel ethanol plant to account for some of the annual variation in production practices and ambient weather conditions. Our data on CO2 production and mold colonization indicate that at temperatures near 12°C, the aerobic stability of DWG is high and that it can be stored for at least a ten day period. When temperatures were close to 22°C, the onset of increased microbial activity and visible mold colonization occurs between four and seven days and both activity and mold ratings were very high by the ninth day in all three experiments. At 32°C, two days may be a more appropriate limit for storage. The simple visual appearance of mold appears to be a reasonable indicator that correlates well (r=0.694) with CO2 production.

Technical Abstract: Maximizing the storability of distillers’ wet grains (DWG) has great influence on the economic, energetic, and carbon balances of fuel ethanol production, yet there is little published data from controlled studies on the deterioration of DWG following its production. Under laboratory conditions, we used biogenic CO2 production to assess the aerobic stability of DWG incubated at three temperatures (12°C, 22°C, 32°C) and compared CO2 production to the appearance of mold and changes in DWG color parameters. This study was repeated three times with fresh DWG collected from a local fuel ethanol plant to account for some of the annual variation in production practices and ambient weather conditions. Our data on CO2 production and mold colonization indicate that at temperatures near 12°C, the aerobic stability of DWG is high and that it can be stored for at least a ten day period. When temperatures were close to 22°C, the onset of increased microbial activity and visible mold colonization occurs between four and seven days and both activity and mold ratings were very high by the ninth day in all three experiments. At 32°C, two days may be a more appropriate limit for storage. Our data does not validate or discount the use of color analysis as indicator of spoilage, but the simple visual appearance of mold appears to be a reasonable indicator that correlates well (r=0.694) with CO2 production.

Last Modified: 8/22/2014
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