Stopping Listeria in food products

Listeria contaminations can send food processing facilities into full crisis mode with mass product recalls and damage to brands. Destroying the bacterium and stopping its spread can be challenging because of the formation of biofilms, or communities of resistant bacteria that adhere to drains or other surfaces.

Researchers at the University of Houston are reporting in the Journal of Environmental Chemical Engineering that cobalt-doped titanium-dioxide (CoO-TiO₂) stops the reproduction of Listeria monocytogenes in both light and dark conditions. This bacteriostatic effect could lead to bacterial control in food products that are not only sealed but also protected from light such as tetra packs, cans and dark glass or plastic bottles. But more toxicity testing is first required in order to determine its safety in food products.

“The addition of cobalt, a heavy metal, drastically improved the effectiveness of titanium-dioxide because now it works under regular human conditions — sunlight, fluorescent light such as light bulbs and even in ‘the absence of light’, like in a freezer,” said Francisco Robles, lead author for the study and associate professor of mechanical engineering technology.

Titanium-dioxide has long been an effective catalyst in the chemical industry with many applications, but it has limitations because ultraviolet light is needed to make it work, according to Robles. “UV light sources are in short supply in sunlight and producing it is expensive and a health hazard (eg, carcinogen), so we set out to find a solution. Making it effective under natural light conditions is significant, and free,” he said.

A naturally occurring mineral, titanium-dioxide is often used in the food industry as an additive or whitening agent for sauces, dressings and powdered foods and is considered safe by the U.S. Food and Drug Administration. It’s also used in sunscreen for its protective effects against UV/UVB rays from the sun.

Sujata Sirsat, study co-author and assistant professor at UH's Conrad N. Hilton College of Hotel and Restaurant Management, believes cobalt-doped titanium-dioxide, whether manufactured directly into food packaging or added to food products, could potentially reduce the risk for large Listeria outbreaks in food processing environments.

“Listeria is a rare foodborne pathogen that can survive in refrigerated conditions. So, if you had a contaminated bowl of potato salad, not only can Listeria survive, it can increase in numbers potentially causing a serious health issue. The cobalt-doped titanium dioxide can potentially stop the spread in its tracks,” said Sirsat, an expert in food safety and public health, who said toxicity testing is needed to determine its safety in food products.

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