Co-product production and handling. The wet milling of corn produces ethanol and three co-products—germ, corn gluten meal, and corn gluten feed. The germ, which is separated from the other kernel constituents after the coarse grind, contains most of the oil contained in the grain. It can be processed to extract the oil, which can then be further refined into food-grade corn oil. This may be done in the same facility as the ethanol plant or sold to a secondary processor.
Corn gluten meal is the protein rich (about 60%) product separated from the gluten-starch slurry and sold as a high-protein animal feed (Ham, 1994). The residual corn fiber separated from the starch-gluten slurry after the second milling step is mixed with evaporated light stillage and dried to produce corn gluten feed, a medium-grade protein product (20-26% of dry matter), which is also used as animal feed (Loe, 2006). Corn gluten feed is similar in fiber content, lower in protein content, and much lower in oil content compared to Distiller’s Dried Grains and Solubles (DDGS) produced in the corn ethanol dry grind process (Ham, 1994). Approximately 2.5 gallons of ethanol, 16.4 pounds of carbon dioxide, 2.1 pounds of oil, 2.6 pounds (dry mass) of corn gluten meal, and 11.2 pounds (dry mass) of corn gluten feed are produced per bushel of corn using the wet milling process (May, 1987).
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