718 Factors affecting the color of dried distillers grains with solubles

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A very common and easily measured metric to characterize dried distillers grains with solubles (DDGS) is color. Drying practices and equipment used by ethanol biorefineries during the early stages of the industry often resulted in dark and burnt DDGS with poor digestibility. These early experiences led to the perception that heating was the only factor contributing to DDGS color. It was our objective to review ethanol production variables to identify additional factors which affect the color of DDGS. Data was collected from 27 POET (Sioux Falls, SD) biorefineries during the period from January 1, 2016 to December 31, 2016. Hunter L color values of DDGS were matched with production variables collected during the ethanol process for each batch of DDGS. Preliminary evaluation of the data identified an obvious difference of dryer type on DDGS color and therefore only data from biorefineries with dual ring dryer technology were selected. This resulted in a data set of 7,575 Hunter L color observations from 16 biorefineries. Data from 57 variables on a batch basis that where shown to be correlated to DDGS Hunter L color were analyzed using the multiple linear regression platform of JMP (JMP Pro, version 12.2.0). All variables had a variance inflation factor less than 2 so multicollinearity was not an issue. The Hunter L Color of DDGS ranged from 41 to 63 for these batches and averaged 54.26 ± 3.49 (SD). Nineteen variables were identified as being related to DDGS color and included in the model. The R2 for the actual color by predicted color for the model was 0.51 and the root mean square error was 2.45. The LogWorth statistic is a logarithmic transformation of the p-value and used to determine contribution of each variable to the model. Greatest LogWorth values were for residual glucose (403.0), syrup dryer temperature (148.6), syrup dryer exit temperature (146.9), normalized syrup addition to the wetcake dryer (88.7), oil separation process temperature (85.7), and syrup percent solids (82.5). In conclusion, this evaluation identified several factors that affect color of DDGS at biorefineries using a similar ethanol process. The data would suggest there are factors that are not routinely collected at biorefineries which may also have an effect on DDGS color. Additional research needs to be conducted to not only better understand factors associated with DDGS color, but also further identify how these factors affect DDGS digestibility and quality.