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ARS Home » Plains Area » Brookings, South Dakota » Integrated Cropping Systems Research » Research » Publications at this Location » Publication #219262
Title: Predicting Stability of Distillers Wet Grains (DWG) using Rapid Color Analysis

Author
item Rosentrater, Kurt
item Lehman, R - Michael

Submitted to: Food and Bioprocess Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2008
Publication Date: 6/12/2008
Citation: Rosentrater, K.A., Lehman, R.M. 2008. Predicting Stability of Distillers Wet Grains (DWG) using Rapid Color Analysis. Food and Bioprocess Technology. DOI 10.1007/s11947-008-0090-x.

Interpretive Summary: The sale of Distillers Wet Grain (DWG), a coproduct from the growing fuel ethanol industry, is essential to the revenue streams of many ethanol plants. Although many studies have investigated the nutritional properties of DWG, and how best to use DWG in livestock diets, little work has investigated the storability and shelf life for these feed materials. The objective of this research was to determine if there is a quantitative relationship between DWG color and either microbial numbers or respiration measured over time Aerobic heterotrophs, molds and yeasts, and carbon dioxide generated by these were measured at t = 0, 1, 2, 4, and 7 d, as were Hunter color values (L, a, b). Aerobic heterotrophs and molds and yeasts grew over time, but time only had a significant effect after t = 4 d. CO2 production, however, significantly increased at each time period. Hunter L and a values appeared to change over time as well, but these differences became significant only at t = 7 d; at this time period Hunter b changed significantly also. Hunter a and b values were negatively correlated with aerobic heterotroph numbers, yeast and mold counts, and CO2 production. Hunter L values, on the other hand, did not exhibit high correlations with any of the microbial values. Using color parameters as predictor variables, response surface regressions were generated, and they appeared to fit the data better than the linear regression of each independent variable separately. Additional research should investigate spoilage criteria, palatability to livestock, and determine how best to implement color changes as indicators of each.

Technical Abstract: Distillers Wet Grain (DWG) is one of the coproducts from the growing fuel ethanol industry. Although many studies have investigated the nutritional properties of DWG, little work has investigated the storability and shelf life for these feed products. The objective of this research, therefore, was to determine if there is a quantitative relationship between DWG color and either microbial numbers or respiration measured over time Aerobic heterotrophs, molds and yeasts, and carbon dioxide generated by these were measured at t = 0, 1, 2, 4, and 7 d, as were Hunter color values. Aerobic heterotrophs and molds and yeasts grew over time, but time only had a significant effect (p<0.05) after t = 4 d. CO2 production, however, significantly increased at each time period. Hunter L and a values appeared to change over time as well, but these differences became significant only at t = 7 d; at this time period Hunter b changed significantly also. Hunter a and b values were negatively correlated with aerobic heterotroph numbers (r = -0.74 for Hunter a; r = -0.77 for Hunter b), yeast and mold counts (r = -0.78 for Hunter a; r = -0.81 for Hunter b), and CO2 production (r = -0.89 for Hunter a; r = -0.87 for Hunter b). Hunter L values, on the other hand, did not exhibit high correlations with any of the microbial parameters (r values ranged from 0.42 to 0.57). Using color parameters as predictor variables, response surface regressions produced R2 values of 0.650, 0.665, and 0.816 for aerobic heterotrophs, molds and yeasts, and CO2 generation, respectively. Additional research should quantify spoilage criteria, the relationship to palatability, and determine how best to implement color changes as indicators of each.