New Starch Removal Process Could Change Corn Wet Milling

By Jim Core
February 21, 2002

An innovative technique to process corn could replace a method used by refiners for more than 100 years.

In the new method, enzymes break down starch and protein while using less sulfur dioxide during what’s called the steeping stage of wet milling. The new process could potentially lower costs and decrease the time needed to produce starch, oil and other important coproducts.

David B. Johnston, a research food technologist at the Agricultural Research Service’s (ARS) Eastern Regional Research Center (ERRC) in Wyndmoor, Pa., says the enzymatic method gets starch yields equal to or better than the conventional process in laboratory and small, pilot-scale trials. He and co-inventor Vijay Singh, a visiting assistant professor from the University of Illinois at Urbana-Champaign, have applied for a patent on the method.

During conventional steeping, corn is soaked for 24 to 36 hours in water and sulfur dioxide to begin breaking down the starch and protein. Afterwards, the corn is coarsely ground to break the germ loose from other kernel components. After removing the germ, which is then used to make corn oil, the remaining slurry is ground to separate the fiber from the starch and protein. Later, the starch is separated out and converted into syrup or into other coproducts, such as ethanol, through fermentation.

Johnston and Singh have found a way to use protease enzymes instead of sulfur dioxide to break down the proteins more quickly. A small amount of sulfur dioxide can still be used to prevent microbial growth during the enzyme treatment step. But overall sulfur dioxide costs would be reduced.

The new method includes a six-hour pretreatment of corn kernels before milling. After soaking the corn kernel in water for about three hours, the ground slurry is treated with enzymes. Then normal wet-milling steps are resumed.

According to Johnston, the method has generated interest from the Corn Refiners Association, whose representatives have visited ERRC’s Crop Conversion Science and Engineering Research Unit to observe the scientists’ results.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.