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Soapstock Waste May Yield New Products

By Jan Suszkiw
March 22, 1999

A biodegradable film made from an oilseed byproduct called soapstock may offer a new material for encapsulating chemicals, packaging fresh produce and other uses.

Gummy and amber-colored, soapstock results from using hexane and other industrial substances to extract and refine edible oil from the seed of cotton, safflower and sunflower crops. For example, cottonseed processors alone generate 60-120 million pounds of soapstock annually. Most goes into animal feedstuffs containing seedmeal.

But oilseed processors are seeking new, more profitable uses, note chemical engineers Sam Kuk and Amy Ballew of the Agricultural Research Service in New Orleans. ARS is the U.S. Department of Agriculture’s chief scientific agency.

About a year ago, Kuk and Ballew began experimenting with ways to exploit soapstock’s cache of plant esters, glycerides, and phospholipids--substances that make it biodegradable, malleable and soluble in both water and oil.

Initially, they faced a problem encountered by scientists before them: how to rid soapstock of water and hexane without eliminating its desirable properties. The answer, they discovered, lay in a combination of treatments, including freeze-drying at -40 degrees Celsius, and fine-grinding. A hydrated paste made from the ground soapstock is also spread onto glass plates or spheres to form thin, flexible films.

The scientists are seeking an industrial partner to help refine the films and explore their commercial potential. One interest is developing a packaging material to wrap fresh produce like bell peppers or cucumbers that perish easily. Another possibility is encapsulating fungicides and other chemicals in slow-release formulations. Studies show that when placed in water, the soapstock capsules degrade at a rate that delays the release of fungicide by about three hours. This may also apply for pharmaceutical compounds.

Scientists also are testing a soapstock gel for hair styling and coloring.

Scientific contact: M. Sam Kuk, Amy Ballew, Commodity Utilization Research Unit, ARS Southern Regional Research Center, New Orleans, LA phone: (504) 286-4552, fax: (504) 286-4419,