Two fraction extraction of α-zein from DDGS and its characterization

Zein was recovered from corn distiller's dried grains with solubles (DDGS) by a modified method using 70% (w/w) aqueous 2-propanol (70-IPA) or 70% (v/v) aqueous ethanol (70-EtOH) solvents, and a commercial method using 88% (w/w) aqueous 2-propanol (88-IPA). Yield, purity, and film properties of the isolated zein were determined. The modified procedure extracted two fractions of zeins: a mostly alpha-zein fraction, and a mostly gamma-zein fraction. The modified method increased alpha-zein yield from 4% to 14%. Enzyme cellulase pretreatment did not improve zein yield, but grinding did. The alpha-zein fraction showed electrophoretic bands at 40, 22, 19, and 10 kDa, corresponding to alpha-zein dimer, alpha(1)-zein, alpha(2)-zein, and delta-zein, respectively. The alpha-zein of DDGS retained its film forming capability. The alpha-zein film of unmodified DDGS was cloudy and rough, unlike the clear and smooth films of alpha-zeins isolated from corn gluten meal and enzyme-treated DDGS. (C) 2011 Elsevier B.V. All rights reserved.