The study examined the efficacy of copper used as an antimicrobial biocide against new strains of E. coli, and although it did not examine O104:H4 (the strain apparent in the spring epidemic in Germany and France), the authors found that all the strains investigated died rapidly on copper.
On a dry copper surface, the investigators showed that 10m E. coli bacteria were eliminated within 10 minutes, while on a wet copper surface, one could expect a ‘total kill’ within around 45 minutes.
Asked about the potential food safety benefits of integrating copper within food processing facilities, Keevil said: “The problem is that people always think of copper as the pure metal. If you’re a French cook, then you know that the best cordon bleu cookery schools use copper pans, they’re expensive. Pure copper isn’t very good in acid conditions, but now there is a whole range of alloys.”
Keevil said that such alloys were never investigated to see if they had antimicrobial properties, but that his team had shown that alloys containing more than 60% copper were antimicrobial.
“So there’s a whole family of copper alloys that could be very beneficially in things like food processing. They’re resistant to acid attack, for example, in contact with foods.”
Integrating copper into plants
Asked how copper could be integrated into facilities, Keevil said:“You might be concerned that staffs are contaminated.In that case a copper alloy surface would protect against worker contamination. The other big issue is that the foods themselves are naturally contaminated. E. coli O157:H7, for example, is present in contaminated beef, Salmonella and Campylobacter in contaminated chicken.”
Keevil noted that these meats could contaminate, say, salads or tomatoes placed on food contact surfaces after they were removed.
“Protecting against staff, you would certainly be looking at door handles, push plates on doors, etc. But if you’re concerned about contaminated food itself, then the actual food preparation area – cutting areas, conveyer belts, etc. are all very important.”
But with copper trading at around $7,500 on the London Metal Exchange, did Keevil accept that the significant premium involved for food processors using the metal instead of stainless steel?
He said: “When I’ve spoken to metallurgists in the copper industry, they tell me there’s very little difference between the price of stainless steel and copper. All I know is that there isn’t that much of price differential.”
Keevil said that previous research on contact surfaces within the food industry also showed that copper was also effective against Listeria on both dry and wet copper surfaces.
We then moved on to the hospital acquired infections, such as MRSA, Clostridium difficile, Acinetobacter baumannii, and again copper was doing a great job,” he added.
Source: http://alturl.com/da68r y Enviromental Microbiology, November 2011
Aporte: M. Josefa Henriquez