Use of copper cast alloys to control Escherichia coli O157 cross-contamination during food processing

The most notable method of infection from Escherichia coli O157 (E. coli O157) is through contaminated foodproducts, usually ground beef. The objective of this study was to evaluate seven cast copper alloys (61 to 95%Cu) for their ability to reduce the viability of E. coli O157, mixed with or without ground beef juice, and tocompare these results to those for stainless steel. E. coli O157 (NCTC 12900) (2 107 CFU) mixed withextracted beef juice (25%) was inoculated onto coupons of each copper cast alloy or stainless steel andincubated at either 22°C or 4°C for up to 6 h. E. coli O157 viability was determined by plate counts in additionto staining in situ with the respiratory indicator fluorochrome 5-cyano-2,3-ditolyl tetrazolium. Without beefextract, three alloys completely killed the inoculum during the 6-h exposure at 22°C. At 4°C, only thehigh-copper alloys (>85%) significantly reduced the numbers of O157. With beef juice, only one alloy (95% Cu)completely killed the inoculum at 22°C. For stainless steel, no significant reduction in cell numbers occurred.At 4°C, only alloys C83300 (93% Cu) and C87300 (95% Cu) significantly reduced the numbers of E. coli O157,with 1.5 and 5 log kills, respectively. Reducing the inoculum to 103 CFU resulted in a complete kill for all sevencast copper alloys in 20 min or less at 22°C. These results clearly demonstrate the antimicrobial properties ofcast copper alloys with regard to E. coli O157, and consequently these alloys have the potential to aid in foodsafety