Publication no. C-2003-0616-05R |  VIEW ARTICLE

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

Mila P. Hojilla-Evangelista (1,2) and Lawrence A. Johnson (1,3). (1) Department of Food Science & Human Nutrition, Center for Crops Utilization Research, Iowa State University, Ames, IA 50011. (2) Presently, Research Chemist, National Center for Agricultural Utilization Research, 1815 N. University St., Peoria, IL 61604. (3) Corresponding author. E-mail: <ljohnson@iastate.edu> Phone: 515-294-4365. Fax: 515-294-6261. Cereal Chem. 80(4):481-484. Accepted January 15, 2003. Copyright 2003 American Association of Cereal Chemists, Inc.

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-ethanol-defatted, flaked corn by using 70% (v/v) ethanol at 60°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°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.