Copper Alloys Surfaces Touted As Pathogen Killers

Three types of alloy surfaces containing at least 90 per cent copper completely eliminate E. coli O157:H7, according to an ongoing UK study of the pathogen-killing properties of the metal.

The study gives machine makers a range of options when deciding on the mix of metals they use to coat the insides of their cooking surfaces, thus providing processors with a better means of eliminating E coli contamination in their products. E. Coli O157:H7 is a harmful bacterium primarily found in raw and undercooked ground beef or foods that come into contact with raw meat.

The study could counter a current trend in the food-processing sector to use equipment made of stainless steel in their plants. Stainless steel is believed to be easier to clean and does not corrode as easily as copper under the frequent chemical cleanings needed to remove harmful pathogens.

While FoodProductionDaily.com has previously reported on the general findings of the study, a press release issued yesterday by the University of Southampton found that silicon bronze, a mix of 95 per cent copper, significantly reduced the E. coli strain in 45 minutes and completely eradicated in 75 minutes.

Brass, which is 85 per cent copper killed the bacteria in three hours. Red brass, which is 93 per cent copper, eradicated it in 4.5 hours. Significant reductions were noted after six hours on Ni- Al bronze (81 per cent copper) and yellow brass (61 per cent copper), the scientists stated.

The tests were done at room temperature and the results compared with those obtained from using stainless steel surfaces. The stainless steel had no effect on the viability of the E. coli at room temperature, the scientists stated.

The tests were also repeated at refrigeration temperature, about 39F. While the stainless steel had no effect on the E. coli, the three alloys with the highest copper content -- silicon bronze, red brass and brass -- eliminated it within three hours.

Jonathan Noyce, the lead author of the study, said it shows that alloys with 90 per cent or more copper content are proven to have significant disinfection ability at both room and refrigerated temperatures.

"Although stainless steel is easily cleaned, it is not intrinsically effective at reducing bacteria," he said. "It would seem that the food processing and preparation environments would benefit from using materials, like copper, that are inherently antimicrobial."

The study was originally published in the June 2006 issue of Applied and Environmental Microbiology.

The Copper Development Association Inc. and the International Copper Association Ltd funded the study.

Escherichia coli O157 is one of the most serious food-borne pathogens worldwide, causing symptoms ranging from diarrhea to hemorrhagic colitis. Cattle is a major reservoir of E. coli O157, therefore outbreaks are primarily associated with consumption of undercooked ground beef, the researchers stated.

Source-Bio-Bio Technology
SRI