Almost all corn oil is expeller pressed, then solvent extracted using hexane or 2-methylpentane (isohexane). The solvent is evaporated from the corn oil, recovered, and re-used. After extraction, the corn oil is then refined by degumming and/or alkali treatment, both of which remove phosphatides. Alkali treatment also neutralizes free fatty acids and removes color (bleaching). Corn oil specifications:
1) appearance: clear and transparent
2) free from foreign and rancid odors and tastes
3) luster: y30, r2.2
Physical-chemical indexes:
1) moisture and volatile matter: 0.1% (max.)
2) foreign matter: 0.05% (max.)
3) acid value: 0.3mg (koh/g) (max.)
4) peroxide value: 10meq/kg (max.)
5) cold test: clear and transparent (frozen for 5.5 hours at 0 o c)
6) un-saphonificated matter: 1.5% (max.)
7) smoking point: 220 o c (min.)