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Sequential Extraction Processing of High-Oil Corn

¹Department of Food Science and Human Nutrition, Center for Crops Utilization Research, Iowa State University, Ames, IA 50011-1061. ²Presently, research chemist, National Center for Agricultural Utilization Research, Peoria, IL 61604. ³Corresponding author. E-mail: ljohnson@iastate.edu.

The Sequential Extraction Process (SEP), a process that uses ethanol to fractionate corn into high-value co-products when producing fuel ethanol, was evaluated using high-oil corn (HOC). Oil and protein recoveries, ethanol-drying capability, and oil and protein properties were compared with those produced from normal soft dent corn (SDC) using SEP. Moisture adsorption capacities (≈24 g of water/kg of corn) and oil recoveries (>95%) were nearly identical for both corn types. However, oil yield from HOC (7.1 g of oil/100 g of corn) was 65% more than that of SDC (4.3 g of oil/100 g of corn). HOC crude oil was less red and contained lower free fatty acid and phosphatide contents than did SDC oil. HOC zein contained higher crude protein content (86% db) than did SDC zein (79% db). The freeze-dried glutelin-rich fractions (GRF) from both types of corn contained >90% (db) crude protein, which meet the criteria of protein isolates. SEP GRF protein isolates had >85% protein soluble in water at pH ≥ 7. Both GRF protein isolates from HOC and SDC were heat-stable, had good emulsifying capacities, and produced highly stable emulsions. They also had substantial foaming capacities, but the foam from HOC GRF protein isolate was significantly more stable than the foam from SDC GRF protein isolate. SEP is a suitable process for recovering oil and protein products from HOC corn when producing fuel ethanol and, if competitively priced, HOC is a preferred feedstock to SDC because of higher yields and qualities of valuable co-products when using HOC.