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Scientists Go Hi-Tech to Battle Food-Borne Microbes


Recently the United States experienced a widespread outbreak of illness traced to California spinach tainted with E. coli bacteria. That was followed by episodes of salmonella poisoning in several states. But even before these events, scientists at Oklahoma State University were working on high-tech improvements in the way vegetables and meats are sanitized.

Federal health officials have told farmers, ranchers, and producers to do a better job of killing E. coli, salmonella, and listeria pathogens on vegetables, animal carcasses, and processed meats. These tiny, food-borne microbes sicken humans and kill an estimated 5,000 Americans each year.

At Oklahoma State University, researchers are refining the common practice of swishing raw foods in a sanitizing solution before they are packaged. Using vats of brine hooked to a high-tech cabinet the size of a small refrigerator, they are producing a different kind of rinse that kills deadly microbes. Meat processing specialist Jake Nelson says the machine is an "electrolyzed-water generator." "It uptakes the brine, passes through some electrodes, passes electric current through the brine, and then you have a separation of the sodium and the chlorine -- There's two outputs that come out of the machine -- an anolyte and a catholyte. The anolyte is essentially the chlorine-based solution" says Jake Nelson.

That solution is hypochlorous acid, not the stronger bleach or plain water that is now used as a rinse in many U.S. food-processing plants. Mr. Nelson says electrolyzed water is commonly used in skin treatments and at health spas, but is relatively new to the food industry. He says vegetables such as spinach and lettuce are vulnerable to microbes from animal manures that often wash into fields. And raw meat is equally susceptible to microbial contamination. Mr. Nelson notes that "during the slaughter process, there's a critical juncture when you go from a dirty animal into a clean carcass. And that takes a skilled employee, a skilled operation. But like everything else, nothing is absolutely foolproof. You still have a raw, fresh-meat carcass when you've finished."

Fresh meats -- carcasses and cuts such as steaks and chops -- have just been added to the products on which the U.S. Department of Agriculture allows sanitizing rinses to be applied. The USDA says it wants to see more testing before it will permit processors to use chemical washes on processed, ready-to-eat meats like hot dogs and cold cuts.

Oklahoma State food microbiologist Peter Muriana says the concentrated batches of chlorine and acid that many operations use to prepare traditional chlorine washes are so hazardous to workers that they must be applied after hours, when the plant is nearly empty. "You know how it is at home with bleach if you get bleach on yourself or in your eye. Here you've got it on a daily basis. Someone has to be working with concentrated containers of it. So there's a way of minimizing risk and hazards to workers."

The ready-mixed hypochlorous acid produced by the generators at Oklahoma State is easier to use than chemical washes that must be mixed -- by employees who sometimes don't get the proportions right. The machine-generated solution appears to be more stable; it does not tend to break down as the product is stored. At the university, the diluted, virtually tasteless hypochlorous acid solution is sprayed on fruits and vegetables and fresh animal carcasses, and -- in higher concentrations -- on floors, knives, nozzles, and work surfaces.

"Bacteria are distributed everywhere," Dr. Muriana points out. "So you want to kill them everywhere. And you can best do that with a sanitizing treatment that can reach everywhere and everything."

In another part of the Oklahoma State University Food and Animal Products Center, horticulturist William McGlynn is working with the state's vegetable farmers to collect microbial samples. Then he's plugging the data into statistical models in order to predict danger zones in the preparation and packaging process. He says heads of lettuce, for instance, are cut from the ground and trucked to a processing plant. There, they are trimmed of stems and excess leaves -- usually by hand -- then chopped, sliced, or shredded.

"The next step would usually be some sort of combination washing and sanitizing step. Following that, it has gone through a water bath, so we need some sort of step to remove that excess water. That's either done by just a simple screen, or sometimes by a light centrifugation -- kind of like what you do in the spin cycle of your washing machine. And then following that would be packaging."

Professor McGlynn says he now has a pretty good idea which stages of the process are most vulnerable to bacterial invasion. But he thinks it will be a few months before he'll be confident enough to tell producers and government food inspectors what he found.

SanAquel LLC, a new company in the little Oklahoma town of Bristow, makes the electrolyzed-water generators in several sizes, suitable for lease by companies large and small. A generator of the size under study for the Oklahoma State slaughtering facility would cost more than $75,000 to purchase. SanAquel is about to move into an abandoned factory, where it plans to also bottle the electrolyzed saltwater so that small operations such as cafeterias and fast-food restaurants can use it as a sanitizer, right out of the jug.

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