Germ contributes about 11% of the kernel weight, contains 45-50% oil and about 85% of the oil kernel. The germ is a distinct entity that can be easily separated and then extracted to produce maize oil, yielding maize germ oil meal as the main by-product.
The germs themselves are obtained from maize processing from wet milling (starch production) or dry milling (maize grits, maize flour, maize meal and ethanol production).
Germs are removed in the wet milling process to facilitate starch extraction, whereas they are removed in the dry milling process to improve the stability of maize grain products for use as food.
In the wet milling process, maize grain is steeped in water and then separated into kernels, from which starch is later extracted, and germs. The germs are washed, dried, and extracted first by mechanical extraction and then by solvent (hexane). Maize germ meal consists of the spent germs and other maize grain fragments.
In the dry milling process, abrading action strips away the germ and pericarp while leaving the endosperm intact. While the endosperm continues through the milling process, the combined bran and germ are aspirated to remove the bran, allowing the germ to be extracted, yielding oil and maize germ meal.