High-Tech Germ Killers / Irradiation, Super-High Pressure Are Among the Ways Being Tested to Prevent Food Contamination

Could food producers literally squeeze the salmonella out of a jalapeno? Or zap the E. coli from lettuce without it going limp? Headline-grabbing food poisonings from raw foods are prompting new interest in technology – from super-high pressure to irradiation – to get rid of some of the bugs. It won’t be a panacea: Far better to prevent contamination on the farm than to try to get rid of it later.

“This is never an excuse for a dirty product,” warns Michael Osterholm, an infectious-disease specialist at the University of Minnesota.

Washing, even with chlorine or other chemicals, only gets rid of surface contaminants, not germs that sneak inside the fruit or vegetable. Enter high-tech options.

At a Virginia Tech laboratory this summer, food scientists subjected small grape tomatoes to what’s called “high-pressure processing” to see if they could squeeze salmonella to death.

It’s been known for decades that massive pressure – the equivalent of two African elephants standing on a dime is how Tech microbiologist Robert Williams puts it – can destroy certain pathogens. The question is how to kill the bugs without smushing the food they’re in.

Key is to choose a water-packed food with few air pockets. Put it in a container of water and apply pressure evenly to all sides. Air pockets will collapse, but waterlogged tissue is more resistant. Grape tomatoes emerged fine, says Tech food scientist George Flick.

But bigger beefsteak-style tomatoes cracked under the pressure. There’s more air inside regular tomatoes than their tiny cousins.

Foods treated by high-pressure processing, or HPP, already are on the market – particularly raw oysters treated to kill the vibrio germs that proliferate in warmer waters, as well as processed meats treated to kill dangerous listeria.

For more delicate raw produce, sliced fruits and vegetables seem to be HPP’s main niche, says Errol Raghubeer of Avure Technologies, a Kent, Wash.-based company that makes high-pressure food- processing equipment sold under the trade name “Fresher Under Pressure.”

First on the market: Sliced avocados and guacamole, after companies realized that HPP treatment killed spoilage germs that rapidly turned cut avocados brown, thus extending the products’ shelf life.

Also arriving are ready-to-assemble fajita meal kits with little bags of HPP-treated fresh, sliced jalapenos. Raw jalapenos have become the prime suspect in the nationwide salmonella outbreak that has sickened more than 1,200 people this summer.

Simple physics is behind high-pressure processing. Another approach under consideration by the Food and Drug Administration is irradiation, zapping fruits and vegetables with enough electron beams or other radiation to kill germs.

ILLUSTRATION: PHOTO

Originally published by The Associated Press.

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