Wet milling, com

The United States wet millers buy ca 15% of the com used in the U.S. (worldwide, wet millers consume about 10% of the com used). There are two dozen com wet mills in the United States ranging in capacity from 600—10,000 metric tons/day. SheHed com is shipped to wet millers by tmck, rail, or barge. 

Some of the information available on designs of com wet-milling plants in which com oil and other products are produced indicate that integration with an alcohol plant may be more efficient than a conventional com alcohol plant. 

During com wet-milling, a 40—50% soHds-starch suspension is treated with a metal hydroxide and ethylene oxide at approximately 50°C to produce DS of 0.1 and the product is purified by filtration and washing. 

Volume 4 Technology of Com Wet Milling and Associated Processes (by P.H. Blanchard)... 

Figure 1 A biorefineiy produces fuels and chemicals from biomass one embodiment today is the com wet mill...

Caransa, A., Simell, M., Lehmussaari, A., Vaara, M., and Vaara, T. 1988. A novel enzyme application for com wet milling. Starch/Stdrke 40, 409-411. 

Johnston, D.B. and Singh, V. 2001. Use of proteases to reduce steep time and S02 requirements in a com wet-milling process. Cereal Chem. 78, 405—411. 

Corn steep liquor (CSL), a byproduct of the com wet-milling process, was used in an immobilized cell continuous biofilm reactor to replace the expensive P2 medium ingredients. The use of CSL resulted in the production of 6.29 g/L of total acetone-butanol-ethanol (ABE) as compared with 6.86 g/L in a control experiment. These studies were performed at a dilution rate of 0.32 hr1. The productivities in the control and CSL experiment were 2.19 and 2.01 g/(Lh), respectively. Although the use of CSL resulted in a 10% decrease in productivity, it is viewed that its application would be economical compared to P2 medium. Hence, CSL may be used to replace the P2 medium. It was also demonstrated that inclusion of butyrate into the feed was beneficial to the butanol fermentation. A control experiment produced 4.77 g/L of total ABE, and the experiment with supplemented sodium butyrate produced 5.70 g/L of total ABE. The butanol concentration increased from 3.14 to 4.04 g/L. Inclusion of acetate in the feed medium of the immobilized cell biofilm reactor was not found to be beneficial for the ABE fermentation, as reported for the batch ABE fermentation. 

Numerous edible and industrial products are manufactured by the com wet-milling industry through further refining. The dollar value of industry product shipments more than doubled (from 3.1 billion to 7.2 billion) between 1982 and 1997 (Table 2.3). 

Com refining plants tend to be located near sources of raw material. In 1992, nearly 75% of the US com wet-milling industry value of shipments was from plants located in Iowa, Indiana and Illinois.1 In the early 1990s, these three states accounted for about 45% of US corn production. Processing plants in the Com Belt are substantially larger than those in locations away from major corn producing areas. 

Rausch KD. Evaluation of the Resistance-Capacitance Method for Detection of Reduced Com Wet-milling [Ph.D. Thesis], Quality Urbana, IL University of Illinois 1993. 

Figure 31.2 gives a block diagram that shows how a com wet-milling processor produces its starch, com syrup, glucose, and fructose syrups. 

The ability to make corn syrups of high quality at a low cost depends upon having a supply of low-cost, high-purity starch. The com wet-milling operation is very efficient in its separation of corn into its constituent parts of starch, water-soluble materials, protein-fiber-rich materials, and corn oil at high yield and low operating costs. 

Harness, J., Com Wet Milling Industry in 1978, Product of the Com Refining Industry in Food, Com Refiners Association, Washington, DC, 1978. 

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