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Comparison of Alkali and Conventional Corn Wet-Milling: 1-kg Procedures

¹Former graduate research assistant, assistant professor, graduate research assistant, and professor, respectively, Department of Agricultural Engineering, University of Illinois, Urbana, IL 61801. ²Current address: Corn Products International, 6500 Archer Avenue, Bedford Park, IL 60501-1933. ³Former graduate research assistants and professor, respectively, Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506. ⁴Professor, Department of Veterinary Biosciences, College of Veterinary Medicine, University of Illinois, Urbana, IL 61801. ⁵Current address: AACC, 3340 Pilot Knob Road, St. Paul, MN 55121-2097. ⁶Corresponding author. Fax: 217/244-0323. E-mail: seckhoff@uiuc.edu

An alkali corn wet-milling process was developed to evaluate the process as a method to produce high purity corn starch and coproducts with added value. Using a single hybrid (R1064 × LH59), the effects of alkali concentration (0.18–0.82% NaOH), time (29–61 min), and temperature (36–75°C) were investigated. Starch yield was not affected by steep time or temperature. Starch yield was optimal at 65.2% using 0.5% alkali. Increasing the concentration of alkali to 0.82% or decreasing it to 0.18% caused a decrease in starch yield of 8–10 percentage points. Other wet-milling products (fiber, germ, and gluten) also were affected. Steep conditions of 0.5% NaOH, 60 min, and 45°C gave optimal starch yield. Comparisons between alkali and sulfur dioxide wet-milling processes, using 1-kg sample size, were performed on 10 commercial yellow dent corn hybrids. The alkali process averaged 1.7 percentage points more starch than the sulfur dioxide process. Each hybrid had a higher starch yield when wet-milled with the alkali method. Alkali wet-milling produced pure corn starch with <0.30% protein (db).