An average maize grain contains in its core an embryo which is known as 'germ' in scientific terminology. When the grain is planted it is this embryo which 'germinates' to produce the new plant. The germ of maize grain which contains nearly 50% oil is separated from the grain by grinding the grain. Natural moisture contained in the germs is evaporated in oven which leaves only oil in the germs. Thereafter, the germs are compressed in a hydraulic press to extract oil. Not all the oil can be extracted by this method as the compressed residue of maize germs still contains considerable amount of oil. Such quantity oil is isolated by treating the residue or the oil-cake as it is called, with solvent such as hexane. After the oil is isolated, solvent hexane is evaporated leaving only corn oil behind.
All in all, the portion of the maize grain surrounding the germ gives corn flour and the de-oiled cake makes nutritious cattle feed while corn oil is preferred over other vegetable oils on account of its low cholesterol content.