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Technology Update: Bacteria Busters

March 22, 2003
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In an era of increasing concern about food safety, a new generation of anti-microbial treatments comes of age



With foodborne illness under the national microscope, it's no surprise that new anti-microbial treatments are also coming into sharper focus.

Of these, perhaps none has been subjected to a more powerful lens than irradiation.

Although it has been endorsed by every major health and governmental agency in the U.S. for the treatment of meat and poultry, irradiation has yet to win a similar seal of approval from many consumer activists, who argue that science simply hasn't made the case that irradiated food is healthy food. Question is, are consumers listening? Recent statistics are hard to come by, but an on-line Time poll conducted in late 1999 found that nearly two-thirds of respondents believe irradiated food is safe. Whether they are willing to purchase it is another question.

Likewise, surveys indicate that companies producing 75 percent of the nation's ground beef have agreed to use irradiation technology, but less clear is how much of their product is, in fact, irradiated. According to the Food Irradiation Processing Alliance (FIPA), a newly formed consortium of irradiation suppliers, irradiated hamburger patties are currently sold in more than 1,500 stores in certain parts of the U.S, and nationally by Schwan's and Omaha Steaks. Irradiated chicken is sold at some retail stores and at restaurants in Florida. Suffice to say that the march to the marketplace as been steady but slow.

And also costly. As FIPA notes, electron beam, x-ray and gamma ray food irradiation facilities are all multimillion dollar propositions. Newer irradiation equipment, notably smaller in-plant or on-line systems, is making the technology more accessible and affordable to processors, but companies are still looking at an investment of one to two million dollars - money they may be reluctant to invest until they can be certain that a radura label isn't tantamount to a scarlet letter. Consequently, one of FIPA's missions is to foster and support industry and consumer confidence in safe commercial use of food irradiation technology - gamma, electron beam or x-ray.

Irradiation alternatives

It's hard to argue that few anti-microbial treatments are as flexible, thorough or simple as irradiation, and yet the controversy surrounding the technology has prompted discussion of alternative or complementary treatments - some of them intended for meats and others for a broader spectrum of applications. It's worth noting that none is necessarily considered a magic bullet in the war on foodborne illness. Rather, most suppliers, researchers and sanitation experts advocate the "multiple hurdles" approach to pathogen reduction, meaning that sound sanitation, handling and storage practices must still figure into the equation.

The use of the anti-microbial agent ozone in direct contact with food products, including meat and poultry, was finally approved by the U.S. Food and Drug Administration (FDA) in June - nearly 100 years after the product was first used to disinfect drinking water. A powerful oxidant, ozone is credited for killing Escherichia coli 0157 more than 3,000 times faster than chlorine. And because it converts to oxygen after the process, it doesn't leave any chemical residues, tastes or odors behind. Instead, the product reverts back to a non-toxic, environmentally safe substance - oxygen. According to supplier Novazone, ozone is not only suitable for treatment of meat and poultry, but also for raw agricultural commodities and grains during storage and transit.

As reported by FE in June, the food industry had been waited a long time for ozone to clear its last regulatory hurdle. In the weeks that followed, BOC and RGF Environmental Group of West Palm Beach, Fla., formed a strategic alliance to market ozone-based applications for the treatment of E-coli, Salmonella and other microbes (See Manufacturing News, page 11). And at least one major food company was reportedly ready to roll out ozone at 70 plant sites.

So far, so good, right? Wrong. In late July, consumer and environmental group Public Citizen requested a stay of action and a formal evidentiary public hearing in the hopes of reversing FDA's approval of ozone. A letter to FDA signed by Wenonah Hauter, director of Public Citizen's Critical Mass Energy and Environment Program, indicated that the request is "due to a variety of concerns, including the formation of chemicals known or suspected to cause cancer and genetic damage." Besides her claim that FDA failed to consider a substantial body of research identifying carcinogenic and mutagenic byproducts of ozonization, Hauter took the agency to task for its incomplete analysis of ozone's bactericidal properties. She wrote that when used to treat samples high in organic matter, "ozone is decomposed by the organic matter before [it] has an opportunity to inactivate microorganisms present on the tissue sample." She also indicated that ozone may not have a reductive effect if bacteria colonies are established or if a food sample is heavily contaminated.

But the larger issue, according to PC, is simply that FDA failed to perform a complete and thorough evaluation of ozone, leading to "material shortcomings in the rationale of [its] ruling." A tempest in a teapot? We'll see.

Other treatments approved in the past few years have found the going a bit easier. Steam pasteurization received a big boost in the late '90s when Cargill, Inc. and its beef processing subsidiary, Excel Corp., announced that the technology would be installed in all of Excel's North American beef plants. In fact, Cargill - along with systems manufacturer Frigoscandia Equipment Group - had a hand in developing the technology, which exposes the meat carcass to a blanket of steam that raises its surface temperature to 185 degrees F, thereby killing bacteria. Having received USDA approval in the late 1990s, the technology has proven especially effective in killing Salmonella, Escherichia coli 0157:H7 and Listeria. High-temperature vacuuming is also USDA-approved, and calls for spraying either steam or hot water on the midline or hindquarters of the beef carcass and then applying a vacuum to remove water from the surface of the meat. A few years back, government estimates indicated that plants processing 85 percent of fed cattle in the U.S. employed the technology.

Meanwhile a handful of other anti-microbial products designed for direct contact with food are showing promise, including lactoferrin, cetylpyridinium chloride and acidified sodium chloride (ASC).

Lactoferrin, of course, is a naturally occurring protein in mammalian milk that is credited with protecting infants from harmful bacteria while their immune systems are developing. The protein made a big splash last year when Farmland National Beef Packing Company announced that it had acquired the commercial development rights to activated lactoferrin, which was developed by researchers at Polytechnic University-Pomona (Calif.) as an anti-microbial treatment for meat. (Farmland provided funding and equipment for the project.) When lactoferrin was isolated from whey and activated with an FDA-approved compound, Pomona researchers found they were able to mimic the protein's naturally occurring functions on the surface of meat carcasses. The protein both removes bacteria from meat surfaces and prevents bacteria from attaching and growing there. Laboratory tests confirmed that the activated lactoferrin was effective in removing more than 30 pathogens, including E. coli 0157:H7, Salmonella and Campylobacter and some microorganisms known to be resistant to radiation. The product is generally regarded as a final step in the carcass-sanitizing process. Because it remains on the meat's surface, Lactoferrin may be able to keep bacteria from binding to the surface for an extended time period.

Cetylpyridinium is a pre-chill, post-chill and pre-package ingredient for use in ready-to-cook, ready-to-eat and processed products manufactured from a broad array of foods, including meat, poultry, fish and fruits and vegetables. Developed by Safe Foods Corp. under the name "Cecure," the product has proved effective against an equally broad range of foodborne pathogens, including Salmonella, Listeria monocytogenes, Campylobactor, and E.Coli. Studies from Kansas State University showed that Cecure, which is found in mouthwashes and throat lozenges, resulted in a six-log reduction of Listeria monocytogenes in ready-to-eat frankfurters, and four-log reduction in Salmonella, E. coli, Campylobacter, Listeria and Staphylococcus at a commercial poultry processing facility. Studies also indicate that Cecure doesn't degrade the flavor, texture, appearance or odor of foods. And because it is stable in water, the product can be misted on products.

The only hitch -- and it's a big one -- is that cetylpyridinium chloride has yet to be approved by USDA or FDA as a food ingredient. However, approval could come soon.

Protecting produce

The two agencies are currently reviewing the use of another relatively new ingredient, acidified sodium chlorite (ASC), for use in comminuted and formed ready-to-eat products, including hot dogs and other sausages. The product, a combination of citric acid and sodium chlorite, is marketed as an aqueous solution under the name Sanova, and has already been approved by USDA and FDA as a food additive on meat, poultry, seafood, and produce.

In a nutshell, ASC attacks sulfide and disulfide linkages, and makes non-specific attacks on amino acid components of bacterial cell components. Like Cecure, the product attacks a broad spectrum of pathogens, including bacteria, viruses, fungi, yeasts, molds and some protozoa. According to Sanova manufacturer Alcide Corporation, ASC is applied at ambient temperatures as either a spray or immersion dip. Its residue is considered safe.

ASC shows particular promise in treating bacteria on fresh produce, for which it recently received FDA and EPA approval. In a paper he presented at Institute of Food Technology's Annual Conference in June, D.E. Conner, a member of the department of Poultry Science at the University of Auburn, (Ala.), noted that while relatively little foodborne disease is associated with produce, the number of reported cases of fresh fruits and vegetables has nevertheless doubled in the last decade.

That makes ASC's performance in such applications all the more welcome. When applied to inoculated fresh fruits and vegetables at 1200 ppm for as little as a minute, the product substantially reduced numbers of Salmonella serotypes, E. coli and Listeria monocytogenes, Conner reported. Typically, treatment resulted in a 3 log reduction of these pathogens on carrots, strawberries, tomatoes, cucumbers, lettuce and apples. However, results varied according to the type of bacteria and produce in question, with Salmonella generally more susceptible to the product than E. coli 0157:H7 and Listeria monocytogenes. While ASC's impact on the microbiological safety of fresh produce is clear, Conner concluded that further research is needed to determine the effects of ASC on produce quality.

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