Products

THE CORN WETMILLING PROCESSIn the corn wet milling process,(Figure 2), the kernel isseparated into its componentparts, and those parts arethen further subdivided andrefined.The wet miller buys shelledcorn which is delivered tohis plant by truck, barge orrail car. Normally #2 gradecorn is purchased, based onU.S. Department of Agriculturestandards. The first stepin the process is to clean thegrain to remove extraneousmaterial such as pieces ofcob, foreign seeds, straymetal, fine dirt, or light unwantedmaterial. It then isconveyed to storage silos,holding up to 350,000 bushels,until ready to go to therefinery.The cleaned corn is transportedto large tanks calledsteeps. Warm water (125 o130 o F) containing smallquantities of dissolved sulfurdioxide is circulated throughthe steeps for approximately40 hours. Soaking softensthe kernel and the dilutesulfurous acid formed byinteraction of the sulfur dioxideand water (SO 2+ H 2O= H 2SO 3), controls fermentationand assists in separationof the starch and protein.During steeping, thesoluble components are extractedfrom the intact kernel.At the conclusion ofsteeping, the water is drainedfrom the kernels and concentratedin multiple effectevaporators to yield concentratedsteepwater. This proteinrich extract may be usedas a nutrient for microorganismsin the production ofenzymes, antibiotics andother fermentation products.The major portion, however,is combined with fiber andgluten in the production ofanimal feed ingredients.The softened corn kernelsnext pass through attritionmills to break them up,loosen the hull and free thegerm from the endosperm.Wateris added to theattrition mills and a thickslurry of macerated kernelsand whole germ results. Becausethe germ at this stagecontains 40-50 percent oil itis lighter than the endospermand hull. Centrifugalforce is used to isolatethe germ.The clean, separated germ isthen dried and the crude oilis removed by mechanicalpresses and/or solvent extraction.The crude oil maybe refined to yield a finequality salad and cooking oilor a raw material for thepreparation of corn oil margarines.The extracted germmeal is used in animal feed.Further information on productionand use of corn oil6