Reassessing Single Criterion for Testing Raw Milk Cheese

The FDA is pausing its testing program for non-toxigenic E. coli in cheese, reassessing use of a single bacterial criterion for pasteurized and raw milk cheese and use of the bacteria as an indicator organism.

According to Dennis D’Amico, PhD, assistant professor in the University of Connecticut Department of Animal Science, the decision to use a single criterion was based on comments received on a draft of the 2009 Compliance Policy Guide (CPG) that recommended a single criterion. The standard of less than 10 MPN/gram was being used by FDA as an indicator of unsanitary conditions in a processing plant.

“This makes sense for a pasteurized milk cheese, whereby the likely source of E. coli would be the processing plant, suggesting that contamination has occurred during cheese manufacture…However, justification for a level less than 10 MPN/gram for raw milk cheese was based on what the scientific literature suggested would be achievable in a raw milk cheese based on probable levels in raw milk and changes in population levels as affected by cheese manufacturing processes (acidification, loss of moisture, etc.).”

The International Commission on Microbiological Specifications, Dr. D’Amico says, states that the presence of coliforms “in many cheese varieties is extremely difficult to prevent completely. With some varieties, if coliforms are present initially, it is virtually impossible to prevent their growth during manufacture or during the ripening period.”

The draft and final FDA CPGs also state that because of the close association of raw milk with the animal environment, low levels of E. coli may be present in raw milk or products made from raw milk, even when properly produced using Good Manufacturing Practices, he says.

“These statements suggest that there should not be a single criterion for raw and pasteurized products and that the use of E. coli as an indicator of unsanitary conditions in a raw milk cheese processing plant is problematic,” Dr. D’Amico says. “In addition, no scientific evidence has been provided to suggest that low limits on levels of non-toxigenic E. coli in a raw milk cheese would do anything to protect public health, especially when coupled with pathogen (STEC) testing.

Gellert Family Professor in Food Safety at Cornell University College of Agriculture and Life Sciences, Martin Wiedmann, PhD, says that “using non-toxigenic E. coli as an indicator where a positive test suggests that a cheese was produced under unhygienic conditions definitely provides more valuable information than testing for coliforms.

“If non-toxigenic E. coli testing is used, the same criteria should be used for raw and pasteurized milk cheeses,” Dr. Wiedmann says, adding that he is “not aware of any scientific information that provides a clear non-toxigenic E. coli MPN cut-off that can be used to identify cheeses that were produced under unhygienic conditions.”

He continues, “Based on some of our work and the available literature, testing for pathogens of concern may be a more effective way to assure food safety.”