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Milling can be achieved by wet milling or dry milling process.
In the dry milling process, first the corn is cleaned, and then water is added to increase the moisture content. The corn tempers for approximately 1 - 3 hours, allowing the moisture to spread throughout the grain. The moisture allows the germ to toughen for easy removal. In the dry milling process, the germ is removed from the endosperm early. This prevents the oil from mixing with the products. Next, the coarsely ground material is sieved to completely remove any more of the germ and bran and then subjected to roller mills and particle size separation equipment. Than all parts are dried before storage.
In the wet milling process, corn is cleaned. The clean corn is soakek for 24 - 36 hours in warm water with sulfur dioxide added. The grain absorbs this sulfur dioxide and swells. Native enzymes begin breaking down the kernel. Next the softened grain is coarsely ground to free the germ from the endosperm. The germs are dried and pressed and the crude oil is extracted. The bran particles are separated from the endosperm. Finally, the gluten is filtered and dried. The starch is washed and vacuum filtered and dried. The starch and oil are the most valuable products from wet milling.