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New Process Improves Wheat Flour Separation

Wheat flour can be separated into gluten and starch more efficiently thanks to a new, environmentally friendly process developed by Agricultural Research Service scientists that uses ethanol instead of water.

Each year, about 2 billion tons of wheat flour undergo processing that yields some 300 million pounds of gluten, a crucial protein in the food industry. After gluten removal, the remaining wheat starch can be used as a thickener or in a host of nonfood products, such as cosmetics or cardboard.

Gluten helps bread to rise by trapping the gases produced by yeast. Without added gluten, whole-grain breads would be too heavy to rise adequately. Added gluten also strengthens hot dog buns so they can open without breaking. Pet foods and some breakfast cereals use gluten as an additional protein source and binding agent.

Since 1835, the predominant commercial separation method has required washing the starch away from the gluten with water—up to 30 tons of liquid per ton of recovered gluten. The resultant sticky gluten dough is dried slowly to keep the protein intact.

The wastewater contains fiber, small amounts of starch and protein, and gums called pentosans. "These leftover ingredients can spoil, so the water can't be reused for long," says ARS chemical engineer George H. Robertson. The wastewater must be expensively treated before it can be discharged.

The new technique that Robertson and colleagues invented at the ARS Western Regional Research Center in Albany, California, replaces the water with ethanol.

"Our process takes about half the time of the traditional methods," says Robertson. "Because the gluten breaks into smaller clumps and dries faster, we can use a lower temperature, which protects the protein properties," he says.

Also, virtually all of the ethanol can be directly reused, requiring no discharge. Another plus: Laboratory tests show the protein may be stronger than that derived from water-separated gluten.

In both processes, filters separate the wheat starch from the liquid after the gluten is removed. The new method (patent application no. 08/879,560) is ready for pilot-scale testing and available for licensing. — By Kathryn Barry Stelljes, ARS.

George H. Robertson is in the USDA-ARS Process Chemistry and Engineering Research Unit, Western Regional Research Center, 800 Buchanan St., Albany, CA 94710; phone (510) 559-5621, fax (510) 559-5818, e-mail

"New Process Improves Wheat Flour Separation" was published in the February 1998 issue of Agricultural Research magazine. Click here to see this issue's table of contents.

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