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 whats 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
Services (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
According to Johnston, the method has generated interest from the
Corn Refiners Association, whose
representatives have visited ERRCs 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.