Add argon for extended shelf life

Packaging food with argon instead of nitrogen gas extends its shelf life, maintains its freshness, and improves its overall quality, according to research presented at the 222nd national meeting of the American Chemical Society.

Taste tests and other studies have shown about a 25 percent improvement in shelf life and quality of argon-packaged foods such as crisps, processed meats and lettuce, reported 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 said.

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.

When foods such as crisps are packaged, the bag's empty space is usually filled with nitrogen.

Trace amounts of oxygen remain, however, which causes food to oxidise - the chemical reaction responsible for crisps becoming stale and cut apples turning brown.

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.

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 said. '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 is also said to improve food safety.

Not only does argon displace oxygen, which many harmful pathogens need to grow it also inhibits microbial oxidases, which are enzymes that increase the rate of oxidation.

Carbon dioxide is often added during packaging to kill microbes, but it also ruins the flavour 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 emphasised. 'We're just stopping it from going bad.'

Spencer, along with David Humphreys, technical development manager for Safeway Stores, built on original research by the French gas company Air Liquide in developing this new argon-packaging technique.