Scientists at the University of Southampton, U.K., have found that E. coli O157:H7, a harmful bacterium primarily associated with raw and undercooked ground beef or foods that come into contact with raw meat, cannot survive on certain copper alloy surfaces. The study, published in the June 2006 issue of Applied and Environmental Microbiology, compares the ability of copper alloys to eradicate E. coli with that of stainless steel, which is commonly used for food processing surfaces.
According to the Unites States Department of Agriculture's Food Safety and Inspection Service, there have been six E. coli-related meat recalls in the past six months. In September 2006 there was a multi-state foodborne illness outbreak linked to E. coli contaminated fresh spinach. E. coli contamination is a serious concern in the food processing and preparation industry. Infections caused by this pathogen can be life threatening, especially in children, seniors and individuals with compromised immune systems.
The Southampton study compared the survival rates of E. coli O157:H7 on several copper alloys and on stainless steel, with regard to both temperature and exposure time. Tests were conducted over a period of six hours at room (72 degrees F) and refrigeration (39 degrees F) temperatures.
The results were significant. While stainless steel had no effect on the viability of the E. coli at room temperature, three copper casting alloys effectively eliminated it, and two others significantly reduced it. The bacteria sample tested on silicon bronze (95% copper) were significantly reduced in 45 minutes and completely eradicated in 75 minutes. Brass (85% copper) and red brass (93% copper) killed the bacteria in 3.0 hours and 4.5 hours, respectively. Significant reductions were noted after six hours on Ni- Al bronze (81% copper) and yellow brass (61% copper).
At 39 degrees F (refrigeration temperature) the stainless steel had no effect on the E. coli, while the three alloys with the highest copper content -- silicon bronze, red brass and brass - eliminated it within three hours.
Copper alloys with 90% or more copper content are proven to have significant disinfection ability at both room and refrigerated temperatures. Dr. Jonathan Noyce, lead author of the study, comments,"Although stainless steel is easily cleaned, it is not intrinsically effective at reducing bacteria. It would seem that the food processing and preparation environments would benefit from using materials, like copper, that are inherently antimicrobial."
The study was funded by the Copper Development Association Inc. and the International Copper Association Ltd.
The University of Southampton is one of the U.K.'s top 10 research universities, with a global reputation for excellence in both teaching and research.
The Copper Development Association is the information, education, market and technical development arm of the copper, brass and bronze industries in the USA.