Putting the Squeeze on Food. Can It Kill the Pathogens?

By LAURAN NEERGAARD

By Lauran Neergaard

The Associated Press

WASHINGTON

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 University of Minnesota infectious-disease specialist Michael Osterholm.

But it’s impossible to prevent all contamination in open fields. Increasingly popular ready-to-eat foods – salads already washed and bagged, fruit peeled and sliced – allow another processing step where a single slipup can introduce pathogens.

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 whether 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.

The 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, said Tech food scientist George Flick, but bigger beefsteak-style tomatoes cracked under the pressure. There’s more air inside the 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, and processed meats treated to kill dangerous listeria.

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

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

Large whole tomatoes don’t fare well, but diced ones can if they’re processed in certain ways, Raghubeer said – and a number of HPP-treated salsas are hitting the market.

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 sickened more than 1,200 people this summer.

A whole jalapeno goes limp when HPP-treated because of its hollow center, but diced jalapenos emerge just as crisp, Raghubeer said.

Simple physics are behind high-pressure processing. A different 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.

Irradiated meat has been around for years; it’s considered particularly useful in the ground beef that is a favorite hiding spot for E. coli. While irradiated foods initially caused some consumer concern, government scientists make clear that the food itself harbors no radiation.

But early on, irradiation left lettuce and spinach limp and made tomatoes mushy. That’s changed, said Minnesota’s Osterholm: “It’s like talking about the TV sets of the 1970s versus flat screens of today,” he said of improved irradiation delivery.

In studies of bagged salads, tailored irradiation doses killed E. coli on nine different types of lettuces without harming the texture or affecting the taste of accompanying ingredients such as tomatoes and cucumbers, said Jeffrey Barach, director of the Grocery Manufacturers Association’s food laboratory. Killing salmonella takes a little more energy, so producers would customize the beam to the need.

Barach’s trade association has petitioned the FDA to allow the irradiation levels, somewhat lower than meat requires, for produce and other ready-to-eat foods, and hopes for approval by year’s end.

The high-tech options add to foods’ cost, meaning they would always be niche products. But parts of the population are particularly vulnerable to food poisoning because of age or health conditions – so that leaves a large market.

crushing pressure

Scientists have long known that massive pressure – described as the equivalent of two African elephants standing on a dime – can destroy certain pathogens. the dilemma

The question is how to kill the pathogens without smushing the food they’re in. The 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.

Originally published by BY LAURAN NEERGAARD.

(c) 2008 Virginian – Pilot. Provided by ProQuest Information and Learning. All rights Reserved.