UVC Safely Eliminates Bacteria

Keeping coliform bacteria counts below required thresholds is a challenge for food processors everywhere, and Washington Potato Co. (Warden, Wash.) understands. “Though we were generally successful in controlling coliform bacteria levels on our products, the time and costs required to achieve control were excessive,” said Nicholas D. Ross, quality assurance and technical services director for the potato processing company.

Washington Potato is an industrial supplier of dry and frozen potato products that are remanufactured by other processors into products such as snacks, soups, stews, and mashed potatoes. One popular Washington Potato product is an IQF (individually quick frozen) diced potato that is minimally blanched prior to freezing. The product sporadically showed initial coliform bacteria counts that were not acceptable to Washington Potato and its customers.

“In efforts to control the problem, we had to treat product transport systems continuously with allowable sanitation chemicals and shut down the process line for major cleaning,” Ross said. “Sometimes we held product in frozen storage to reduce counts and/or sold the held product to customers with less stringent requirements, for example, for animal feed applications. Though this strategy was effective from a product safety standpoint, it was not efficient or economical.”

Giving UVC a Tumble

While searching for solutions at a regional food processing show, Ross learned of a new technology from Reyco Systems Inc. (Meridian, Idaho) that harnessed the germicidal effects of UVC light (ultraviolet light in the C band wavelength) installed in custom-designed tumbling drums for decontamination of food surfaces. Used for many decades for surface and air disinfection and water purification, UVC is scientifically proven to disrupt the DNA or RNA structure of bacteria, viruses, molds and fungi, and yeast. UVC will kill the gamut of microbial contaminants, whether naturally occurring or the result of bio-tampering, including Listeria, Escherichia coli, Salmonella, Staphylococcus, and other microorganisms.

UVC is safe to use, leaves no surface residue, and will not chemically alter food products. Unfortunately, conventional-style UVC devices like those in use for the last several decades lose much of their germicidal effectiveness—or killing power—when operating in cold or moving air conditions, such as those encountered in the processing of refrigerated and frozen foods.

To overcome this limitation, Reyco uses the UVC Emitter, a new-generation device designed and manufactured by Steril-Aire Inc. (Burbank, Calif.) to deliver high-output germicidal energy at low temperatures without loss of efficacy. In multiple studies, the UVC Emitter has been shown to eliminate 99.9% of microbial contaminants on the surface of food products. The United States Department of Agriculture and the Food and Drug Administration have approved UVC for surface decontamination, with no labeling required.

Steril-Aire has marketed the devices since the mid-1990s for mold and microbial control. In addition to their application in the food industry, they are widely used in HVAC systems in hospitals, laboratories, schools, and commercial and government buildings to improve indoor air quality, save energy, reduce coil-cleaning costs, and control infection.

Reyco has licensed a patent-pending methodology incorporating these devices into a tumbling drum that ensures maximum UVC exposure to all surfaces of the product.

Small, portable machines are available to prospective customers for on-site demonstration and testing. “Test results from one of these portable units convinced us that the system worked, and we made the commitment to purchase a permanent tumbling drum for our processing line,” Ross said.

Custom-Designed Drum

The machine designed and installed by Reyco uses a customized tumbling drum that can process about 14,000 pounds of product per hour, easily handling Washington Potato’s requirements, with capacity to spare. Inside the drum are 32 single-ended UVC Emitter tubes in two fixtures designed to withstand wash-down with water and cleaning chemicals. The UVC lights shine continuously to bathe the diced potatoes in germicidal light as the drum gently lifts and rolls the product to make sure all surfaces are decontaminated. The light tubes are wrapped in shatter-resistant plastic sheathing as a safeguard in the unlikely event of tube breakage.