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Scratched Surfaces May Trap Bacteria During Food Processing

Studies examine new countertop materials, cleaners to cut contamination

WEDNESDAY, Sept. 10, 2008 (HealthDay News) -- Minute particles of food soil on surfaces can help bacteria survive industrial cleaning procedures in food processing factories, which may lead to possible contamination of food with pathogenic bacteria, say researchers at Manchester Metropolitan University in the United Kingdom.

"Tiny amounts of soil are enough to provide nutrients and a reservoir for contaminating bacteria to survive the cleaning process, leading to food spoilage later. The soil should be identified to make sure effective cleaning regimes are used on food preparation surfaces," researcher Dr. Kathryn Whitehead said in a Society for General Microbiology news release.

She and her colleagues compared different methods for detection of food residues, including chemical and physiochemical techniques, microscopy and rapid industrial methods such as ultraviolet (UV) light. They found that standard ultraviolet (UV) light and detection techniques may not detect the tiny quantities of food soil, which can even adhere to stainless steel surfaces.

The researchers concluded that more complex analytical methods are the most effective in identifying food soil and developing appropriate cleaning procedures.

"Some methods are not as sensitive as others at detecting food residue and microorganisms in the food industries. A rapid industrial technique using UV light may be optimized to detect soil. Our results also showed that different techniques may be better suited to different disciplines," Whitehead said.

Knowing the type of food soil build-up on food surfaces can help in determining the best approach to removing the soil.

"By using more precise methods to detect food residue and microorganisms on surfaces, it may be possible that different cleaners could be used to target key fouling components," Whitehead said. "We hope our work will lead to a greater level of hygiene in the food industry."

The research was expected to be presented Wednesday at the Society for General Microbiology Autumn meeting, in Dublin.

Another Manchester Metropolitan University study expected to be presented at the same meeting concluded that titanium work surfaces in food factories could reduce the number of food poisoning cases every year, because some pathogenic bacteria have more difficulty attaching to titanium than to stainless steel.

Abrasion, constant cleaning and impact damage can cause work surfaces to become scratched.

"It is important that surfaces in a hygienic environment are kept clean. Scratches may entrap microorganisms such as Escherichia coli and protect them from being removing during cleaning," researcher Adele Packer said in a society meeting news release.

"We measured scratches found on different surfaces and reproduced them in our lab. We coated the surfaces with titanium so that they all had the same chemistry, and the only difference was the surface roughness," Packer said.

After they cleaned the surfaces, the researchers examined them for bacteria retention and found that the shape of bacteria was a factor. Rod-shaped Listeria remained in tiny scratches less than 0.5 micrometers across, and round Staphylococcus bacteria remained in scratches that were 1 micrometer across.

"The results show that surface scratches retain bacteria well if they are of comparable size. The more tightly the bacteria fit in the scratches, the more difficult they are to remove during cleaning," Packer said. "Our findings indicate that titanium coating may have a role to play in reducing the attachment of E. coli to food contact surfaces; E. coli cells attached to stainless steel much better than titanium."

More information

The U.S. Department of Agriculture has more about food safety.

SOURCE: Society for General Microbiology, news releases, Sept. 9, 2008
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