New food packaging technique improves quality, extends shelf life

August 26, 2001

CHICAGO, August 26 -- Packaging food with argon instead of nitrogen gas extends its shelf life, maintains its freshness, and improves its overall quality, according to research presented today at the 222nd national meeting of the American Chemical Society, the world's largest scientific society.

Taste tests and other studies have shown about a 25 percent improvement in shelf life and quality of argon-packaged foods such as potato chips, processed meats and lettuce, reports Kevin C. Spencer, Ph.D., senior scientific and technical advisor for the British grocery chain Safeway Stores plc. Some products, such as fresh pizza, have been improved 40 to 50 percent, he says.

Nearly 200 argon-packaged foods already can be found on grocery store shelves in the United Kingdom, and several companies are exploring opportunities to introduce these products to the United States. Argon is a safe, benign gas that has been used to preserve everything from wine to the U.S. Declaration of Independence.

When foods such as potato chips are packaged, the bag's empty space is usually filled with nitrogen. Trace amounts of oxygen remain, however, which causes food to oxidize -- the chemical reaction responsible for potato chips becoming stale and cut apples turning brown -- and spoil. Spencer and his team found that replacing nitrogen with argon removed oxygen more efficiently, because argon is denser than nitrogen and fills spaces more completely.

"Which means that, in the case of potato chips, at any given point in time, potato chips packaged our way are better than potato chips packaged using standard methods," says Spencer.

Despite argon's superior results, it has taken nearly ten years to make argon packaging commercially viable because, volume-for-volume, argon is more expensive than nitrogen. "When people try to put argon through nitrogen systems, it tends not to work very well," Spencer says. "You've got to adjust the system to deliver the argon as if it were a liquid." In these modified packaging systems, argon is four times more efficient at displacing air than nitrogen, making the difference in cost negligible.

Argon also improves food safety. Not only does argon displace oxygen, which many harmful pathogens need to grow, it also inhibits microbial oxidases -- enzymes that increase the rate of oxidation. Carbon dioxide is often added during packaging to kill microbes, but it also ruins the flavor and freshness of foods. Argon enhances the effectiveness of carbon dioxide by weakening microbes, thereby enabling food suppliers to use less carbon dioxide.

"Nothing we are doing is adding anything to the original product," Spencer emphasizes. "We're just stopping it from going bad."

Spencer, along with David Humphreys, technical development manager for Safeway Stores plc, built on original research by the French gas company Air Liquide in developing this new argon-packaging technique.
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The paper on this research, AGFD 9, will be presented at 9:50 a.m., Sunday, August 26, at McCormick Place South, Room S505A, Level 5, during the symposium, "Freshness and Shelf Life of Foods."

Kevin C. Spencer, Ph.D., is an independent site systems analyst for the food industry. He is based in Oak Brook, Ill.

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American Chemical Society

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