Clifford Hall, NDSU Department of Plant Sciences
The original proposal was to include the use of super critical fluid extraction as a means to recover pigments and antioxidants. Before supercritical fluid extraction could be carried out, characterization of the DDGs was necessary to insure that the optimal extraction would be completed by Thar Technologies. The delay in completion of the project related to the inability to schedule a time with Thar Technologies. However, we were able to obtain a supercritical extraction unit from the USDA. Prior to completing the extraction using supercritical fluid, we did some preliminary work to identify the impact of DDGs moisture content on extraction efficiency. The moisture contents explored range from 0 to 30% moisture. The high moisture represented the wet distiller’s grain while 0% represented lab dried DDGs. The lab dried DDGs were completed using three different methods to determine if extraction efficiency was affected by the drying method. The extraction efficiency was the same for each product and thus the use of the simplest and most inexpensive drying method (i.e. air oven drying) is recommended to reduce moisture content to a level between 10-15%. At these moisture levels, comparable extraction efficiencies were observed. The majority of the DDGs obtained from ethanol plants were close to 15% moisture and thus no additional drying is necessary. Corn had similar moisture contents. Based on the information collected, we moved forward with the supercritical carbon dioxide extraction method. We also used a solvent extract method as a means to compare extraction methods.
Experiments were also completed on deodorization of the DDGs extract. Unlike corn extracts, DDGs extracts carry an odor as a result of ethanol production. We used several techniques to deodorize the DDGs. Steam distillation of the DDGs extract resulted in slight reduction of the odor. The amount of time needed for the odor reduction was too long and thus a different approach for deodorization were completed. Saponification was the technique selected as method to remove the odor. Although slight reduction in the oil color occurred, a nearly odorless final extract containing color and antioxidants was obtained after the saponification method. Developing an odorless extract is significant because an ingredient added to a food cannot contribute negatively to the sensory quality of the food. However, the loss of extract yield occurred during deodorization and thus we opted not to deodorize the extracts due to the loss of extract yield. The supercritical carbon dioxide extraction method produced a DDGs extract with less odor than the hexane extracted DDGs. Additional research is needed to optimize the deodorization of the DDGs.