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Effects of Alkali Debranning, Roller Mill Cracking and Gap Setting, and Alkali Steeping Conditions on Milling Yields from a Dent Corn Hybrid

¹Postdoctoral research associate, former graduate research assistant, former research technician, former research technician, assistant professor, professor, and professor, respectively. Department of Agricultural Engineering, University of Illinois, IL 61801. ²Current address: Corn Products International, 6500 Archer Ave., Bedford Park,60501-1933. ³Corresponding author. Fax: (217)244-0323. E-mail: seckhoff@uiuc.edu

Starch yield was significantly affected by all three main unit operations in alkali wet-milling (debranning, roller milling, and steeping). The conditions for the three unit operations were studied using a single hybrid. Studies on debranning showed that optimal separation between pericarp and corn endosperm was obtained when corn was soaked in a 1.5–2% NaOH solution at 85°C for 5 min. Passing debranned corn through smooth roller mill once or twice did not affect the product yields, but passing the corn through the roller mill three times decreased the germ yield because of a large amount of broken germ. A 62% higher processing rate could be achieved when passing corn through the mill twice than by passing it through the mill once. The gap should be set at 2.0 mm when passing corn through the mill once, and it should be set at 3.5 mm for the first pass and 2.0 mm for the second pass when passing corn through the mill twice. Starch yield was more sensitive to NaOH concentration and steep temperature than to steep time. The highest starch yield was obtained when steeping corn in 0.5% NaOH for 1 hr at 45°C.