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Technology Slays Salmonella on the Farm

Posted on: Tuesday, 29 July 2008, 00:40 CDT

Attention grabbing food poisonings in recent days have sparked new interest in using technology to rid raw produce of unwanted bacteria.

Experts say it’s easier 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.

Farmers allege it's impossible to prevent all contamination in open fields. Popular ready-to-eat foods including pre-washed and bagged salads allow another contamination opportunity during the processing step where a single slip-up can introduce pathogens.

Washing produce, even with chlorine or other chemicals, only gets rid of surface contaminants. Washing does not kill germs that sneak inside the fruit or vegetable. Some scientists believe technology is the missing link in protection against food borne diseases.

Food scientists at a Virginia Tech laboratory this summer, 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 can destroy certain pathogens. Tech microbiologist Robert Williams says it’s the equivalent of two African elephants standing on a dime. The question is how to kill the bugs without ruining the food they're in.

The key to success is to choose a water-packed food with few air pockets. It’s placed in a container of water and pressure is applied evenly to all sides. The air pockets will collapse but the waterlogged tissue is more resistant.

Tech food scientist George Flick says the grape tomatoes emerged fine. He noted bigger beefsteak-style tomatoes cracked under the pressure, because there's more air inside the regular tomatoes than their tiny cousins.

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

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

Sliced avocadoes and guacamole were the first to hit the market, when companies realized that HPP treatment killed spoilage germs that rapidly turned cut avocadoes brown, thus extending the products' shelf life.

Raghubeer says whole large tomatoes don't fare well but diced ones can if they're processed in certain ways. A number of HPP-treated salsas are expected to soon hit grocery aisles.

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

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

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, and it's considered particularly useful in killing E. coli found in ground beef.

While consumers were initially concerned over irradiated foods, government scientists make clear that the food itself harbors no radiation.

In the early days, irradiation left lettuce and spinach limp and made tomatoes mushy. Minnesota's Osterholm says that has changed, "It's like talking about the TV sets of the 1970s versus flat screens of today," he says of improved irradiation delivery.

Jeffrey Barach, director of the Grocery Manufacturers Association's food laboratory, said tailored irradiation doses killed E. coli on nine different types of lettuces without harming the texture, or affecting the taste of accompanying ingredients like tomatoes and cucumbers. He pointed out 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, which are slightly lower than meat requires. Barach is hoping for approval by year's end.

Both high-tech options add to the produce's overall cost, meaning they'd always be something of a niche product.

However, a natural market could span from segments of the population that are particularly vulnerable to food poisoning because of age or health conditions.

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On the Net:

• University of Minnesota
• Virginia Tech

Source: redOrbit Staff & Wire Reports

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