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Food Pathogen Interventions: Spotlight on UV

Editor’s Note: This article is part of a series on new and novel food pathogen interventions, based on presentations at the Food Pathogen Interventions Symposium in Seattle, WA on April 27, 2011.

Last week, a group of scientists and food safety leaders came together at a conference in Seattle to share their expertise on various techniques for guarding against contamination during food production. 

The Foodborne Pathogen Interventions Symposium was a day-long event designed to teach seafood producers about emerging technologies to make food safer, and to help attendees understand the basics of implementing new techniques — from testing to regulatory concerns to inspiring consumer confidence in the new production step.

The symposium was hosted by the Seafood Product Association (SPA) last Wednesday, the very same day the latest guidelines on seafood safety were released by the U.S. Food and Drug Administration (FDA). 

The theme of the event was “hurdles” — putting as many barriers as necessary between foodborne pathogens and the table. 

“In addition to a good strong sanitation program, another concept we should use is the ‘hurdles’ concept, where we have multiple interventions that will supplement your strong sanitation programs to prevent food safety issues,” said Kenny Lum, president of the SPA and coordinator of the event. 

Participants were encouraged to identify all stages at which harmful microbes could come into contact with their food products, and to implement appropriate pathogen-reduction steps at those points.

Speakers noted that the new technologies should not be used in place of other steps to avoid contamination, nor as a safety net for catching food safety mistakes in other areas of production, but as a complement to an all-around safe system.

And before introducing one of these technologies, producers must be sure that the step reduces the targeted pathogen to a negligible amount, noted Mary Losikoff, microbiology and policy expert at FDA’s Center for Food Safety and Nutrition.

“You need to constantly reassess your hazard analysis, and the intervention needs to be validated,” said Losikoff.  “Verification [then] ensures that a previously validated process is working as intended.”

Eight types of new or novel pathogen interventions were discussed at the conference. Each one is more effective on some types of food than on others, and works better at different phases of processing.

Over the next few days, Food Safety News will profile some of the technologies presented at the conference, beginning today with a spotlight on Ultraviolet Light. 

Ultraviolet Light 

Presented by Dr. Keith Warriner, associate professor of Food Science at the University of Guelph

Ultraviolet light has been used in the food industry for decades, but instruments for delivering it continue to evolve. It can be used to decontaminate the air in a production facility, sanitize the surfaces of both products and their packaging, and to clean liquids such as water or juice. UV light can be administered in a variety of ways, including via a tumbling drum (for liquids), a wand or a tunnel of lights.

While many UV-based systems were prohibitively expensive in the past, many, such as the excimer lamp, have become more affordable over time, according to Warriner. 

One of the main advantages of UV is its versatility, in that it can be used on many foods, as well as the air. 

“I’m getting more and more calls from people saying, ‘How do we decontaminate the air? How do we prevent cross-contamination between high-risk areas and low-risk areas?’ ” said Warriner.

UV is generally a low-risk technique, with the exception of a few potential side effects. If workers eyes are exposed to UV light, it can easily cause blindness, Warriner said. It is also known to produce ozone, which can be harmful to humans if not controlled.  Finally, many traditional UV-producing lights use mercury to run. This element can pose a health threat if released into the atmosphere. 

UV light is extremely effective against pathogens, according to Warriner. 

“It’s certainly very highly antimicrobial, provided you can get the photons to the actual target,” he said.

That, Warriner said, is one of the biggest difficulties associated with UV light. In order to get photons to the microbes, UV machines must be able to scatter light photons at various angles so they can reach under anything that might shadow it — fish scales, lettuce leaves shadowing other leaves, or ridges of material like stainless steel, for example. UV light cannot penetrate biofilm, nor can it reach into spores on fibrous packaging.

Opaque liquids such as milk also pose difficulties to UV lights, which cannot penetrate them unless they are mixed around so that each part of the liquid is exposed to the UV photons.  

Another dark side to this light is the fact that, if used in large amounts on some sensitive foods, it can change the food’s characteristics. For instance, it can deplete antioxidants, cause a sulphuric odor in beer, and bleach food. 

UV light is currently approved for use on foods, provided that it is applied at a certain wavelength and that radiation sources don’t emit too much mercury. Because it cannot penetrate into foods, it is applied only to their surfaces.

While it is now used to disinfect some foods, as well as apple juice, UV is employed predominantly for water sanitation.

Warriner predicts this will change, and that UV treatment will be used more frequently in the near future. 

“I think that what people are expecting of UV is that it’s going to expand into a lot of different areas,” he said. 

One technology Warriner thinks could bring UV to this level is the UV-LED light, which is mercury-free, light and compact, and generates no ozone. 

“It’s one of those technologies that’s on the verge,” Warriner said. “They really expect them to improve, a bit like the microchip. They’re the next big thing in the UV field,” he said. 

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