Optimizing Extraction of Zein and Glutelin-Rich Fraction During Sequential Extraction Processing of Corn

This study was conducted to improve yields and qualities of corn protein co-products produced by the sequential extraction process (SEP), a process using ethanol to fractionate corn in producing fuel ethanol. A two-stage extraction protocol was evaluated to recover zein and subsequently recover a glutelin-rich fraction (GRF). After the simultaneous oil-extraction and ethanol-drying step of SEP, zein was extracted from the anhydrous-ethanoldefatted, flaked corn by using 70% (v/v) ethanol at 60(degree)C for 1.5 hr in a shaking water bath. Zein was recovered by ultrafiltering and then drying in a vacuum-oven. Zein yield was 65% of the available zein in the flaked corn. SDS-PAGE band patterns of the recovered zein closely resembled that of commercial zein. After zein extraction, the GRF was extracted using 45% ethanol and 55% 0.1M NaOH at 55(degree)C for 2 hr. The extract was concentrated by ultrafiltration and then freeze-dried. GRF yield was approximately 65% of the available protein. Freeze-dried GRF contained 90% crude protein (db), which classified the protein as a protein isolate. As with the protein concentrate from the original SEP, the GRF isolate was highly soluble in water at pH > 7, had good emulsifying and foaming properties, formed stable emulsions, and was heat-stable.