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Use of Proteases to Reduce Steep Time and SO₂ Requirements in a Corn Wet-Milling Process

¹United States Department of Agriculture, Agricultural Research Services, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, PA 19038. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ²Corresponding author. E-mail: djohnston@arserrc.gov Phone: 215-836-3756. Fax: 215-233-6406. ³Department of Agricultural Engineering, University of Illinois, 360H, AESB, 1304 W. Pennsylvania Ave, Urbana, IL 61801.

To eliminate the diffusion barriers associated with enzyme addition during conventional steeping, we have developed a two-stage milling procedure to evaluate the effects of enzyme addition on corn wet milling. The current study compares the effects of the addition of commercially available enzyme preparations during conventional steeping to their comparable addition in the two-stage procedure. Results are presented in terms of yields of fiber, starch, germ, and gluten. The results demonstrate that the application of enzymes to the normal steeping step of wet milling is not an effective means of decreasing the steeping time or sulfur dioxide usage. Only when specific enzymes are added to the hydrated ground corn, using the modified two-stage procedure, are enzymes effective in decreasing the steeping time and sulfur dioxide requirements. The overall steeping time with the two-stage modified procedure ranges from 6 to 8 hr, representing a 67–83% reduction over the conventional process. The modified process greatly decreases, and possibly eliminates, the need for sulfur dioxide addition, while producing starch yields and quality equivalent to that from the conventional process.