Clamshells, wheat and burgers - the next fast-food craze?

SAN DIEGO, April 2 - Those amber waves of grain could turn up in your local fast-food restaurant before long in the guise of "clamshells" - the foldout containers that hold burgers and other sandwiches. Researchers with the U.S. Department of Agriculture have used wheat to make sandwich containers that are more environmentally friendly than the old polystyrene clamshells and keep food warmer than the cardboard containers now in vogue.

The findings, which could be a boon for wheat farmers as well as consumers, were presented today in San Diego at the 221st national meeting of the American Chemical Society, the world's largest scientific society.

Several years ago, many fast-food chains switched to cardboard food containers in response to environmental concerns that polystyrene clamshells did not easily degrade in landfills and contained CFCs (chlorofluorocarbons), which damage the Earth's delicate ozone layer. But there are trade-offs, according to chemist Geoffrey Nobes who reported on the study. Cardboard is "more expensive, heavier and more complicated to make," he says. "And it doesn't keep it [food] as warm."

Nobes is with the USDA's Agricultural Research Service, Western Regional Research Center, in Albany, Calif. He and other researchers there are testing biodegradable clamshells made from wheat - specifically, fiber from the wheat stalk (straw) and starch from the wheat kernels. "The resulting products [containers] are starch-based foam composites with mechanical and thermal properties rivaling those of polystyrene," the researchers report.

"Our starch-based containers are biodegradable," Nobes pointed out. "In fact, if people have a compost [pile] in the backyard, they could throw these containers in the compost."

Biodegradable food containers made with starch aren't a new idea. They are "already being used in the U.S. by a manufacturer of potato starch-based clamshells," Nobes said. "But our ingredients, wheat starch and wheat straw, are less expensive."

The wheat-based containers have fared well in testing so far, according to Nobes. They keep food warmer and insulate better than those made with potato starch or cardboard, although they are not quite as effective as polystyrene, he said.

Nobes and co-researchers Gregory Glenn and William Orts extract starch from the kernels, grind the straw into fiber and then mix both with water. They pour the resulting batter into a mold and bake it. "It's basically like making waffles," Nobes explained.

The fiber from the straw serves as an insulating filler that forms the clamshell. Nobes likens the starch to a glue that holds the fiber together. "We've determined that the interaction between the fiber and the starch is really important in terms of how strong the container is," Nobes said. "You need to have a good contact, or adhesion, between the starch and the fibers."

One problem still to be addressed is how the clamshells made from wheat stand up to moisture. "They tend to soften when wet," Nobes said. "There's probably some coating that may need to be applied," he acknowledged, "but we hope to be able to avoid that."

Straw isn't the only fiber the scientists examined. "We've looked at everything from softwood fibers, like you would find in your newspaper, to hardwood fibers, and rice and wheat straw," Nobes said.

Straw has a few diverse markets, such as baskets, bedding for animals, erosion control and even housing construction, but much of it is burned or plowed under, according to Nobes. "If wheat straw can be used for biodegradable food containers, farmers could have an additional source of income," he said. There are more than 60 million acres of wheat fields in the United States that yield more than 30 million tons of wheat annually, Nobes added.

If further testing is successful, Nobes says the wheat clamshells could be on the market in two or three years.

The paper on this research, CELL 39, will be presented at 10:45 a.m., Monday, April 2, at the San Diego Convention Center, Room 11B.

Geoffrey A. R. Nobes, William Orts and Gregory Glenn are with the U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, in Albany, Calif.

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