FACTORS AFFECTING OIL EXTRACTION/WATER ADSORPTION IN SEQUENTIAL EXTRACTION PROCESSING OF CORN

Authors: Hojilla-Evangelista, Milagros - Mila; Johnson, Lawrence

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2002
Publication Date: 8/1/2002
Citation: HOJILLAEVANGELIST, M.P., JOHNSON, L.A. FACTORS AFFECTING OIL EXTRACTION/WATER ADSORPTION IN SEQUENTIAL EXTRACTION PROCESSING OF CORN. JOURNAL OF THE AMERICAN OIL CHEMISTS' SOCIETY. 2002.

Interpretive Summary: The Sequential Extraction Process (SEP) is another method to produce ethanol from corn in a potentially more-economical manner. An important step in SEP is the extraction of corn oil using ethanol and the simultane- ous adsorption of water from ethanol, producing 99 percent alcohol, which can be used for fuel. However, this step in SEP still needs to be improved dso that it can produce even drier ethanol bacause the fuel industry requires no more than 0.5 percent moisture. The proteins (zein) that are removed with the oil must also be reduced further or eliminated all together to make SEP more efficient. The improvements that we initiated involved factors such as solvent-to-corn ratio, corn moisture content, and number of extraction stages. When more solvent was used to extract the oil, drier ethanol, greater oil yields and less co-extracted protein were obtained. Using too-dry corn (less than 1.12 percent moisture) decreased oil yields and increased protein loss. On the other hand, increasing the corn moisture content led to the recovery of ethanol with higher-than-acceptable water content. To make SEP faster, the number of extraction stages was reduced from seven (originial SEP) to five, and doing so had no negative effects on ethanol-drying, oil yields and protein co-extracted with oil. When changes based on these findings are incorporated in SEP, the process will meet the fuel industry's specification and make SEP a more cost-effective way to produce ethanol.

Technical Abstract: The sequential extraction process (SEP) uses ethanol to extract oil and protein from cracked, flaked, and dried corn, and the dried corn simultaneously dehydrates the ethanol. Value-added co-products are possible, potentially making production of fuel ethanol more economical. The effects of solvent-to-corn (S/C) ratio, corn moisture content (MC), and number of extraction stages on ethanol drying, oil recovery, and protein loss during the simultaneous oil extraction/water adsorption step of SEP were evaluated. Extractions were carried out by using both aqueous ethanol and ethanol:hexane blends at 56 degrees C. The S/C ratios tested were 3:1, 2:1 (control), 1.5:1 and 1:1 (w:w). More anhydrous ethanol, greater oil yields, and less co-extracted protein were obtained with higher S/C ratios. Less anhydrous ethanol and lower moisture adsorption capacities were obtained when the corn MC was greater than 1.12 percent. Oil yields gradually decreased with drier corn, while protein loss increased when corn MC was less than 1.12 percent. Reducing the number of extraction stages from seven (original SEP) to five did not affect ethanol drying capability, oil yields, and protein co-extracted with oil. Using ethanol:hexane blends resulted in more anhydrous ethanol, higher oil yields, and less amounts of protein co-extracted with oil.