Food Safety Magazine, June/July 2011

prove precision, but some general principles are known and we can apply calculations of exposure scenarios from that report. Let’s start with a hypothetical RTE product inadvertently recontami-nated with only 10 organisms per gram. Unchecked Listeria growth during refrigerated storage will result in a product with levels up to log 8–9 colony-forming units per gram (i.e., 100 million–1 billion organisms per gram) within 3 to 4 weeks. Then, if a pregnant woman were to consume two ounces of the product at that point, her risk of a miscarriage could be around one in 7,500. This is a serious risk. If the same product is formulated to inhibit Listeria growth to 1 or 2 logs, that is, the numbers of Listeria would be limited to 100 to 1,000 per gram, then the risk profile decreases to between one in 75 million and one in 50 billion. It is this significant risk reduction that led many companies to add lactate and diacetate to their formulations (Figure 1).

on environmental controls to prevent recontamination after processing. Alternative 2 adds either a growth inhibitor ingredient in the RTE product or a post-packaging treatment that is validated to reduce the number of Listeria. Alternative 1 represents the use of both a growth inhibitor and a post-package treatment. The regulations also describe regulatory consequences of finding Listeria on food contact surfaces in the processing facility with differences for each alternative with respect to finished product sampling. Alternative 1 and 2 systems offer manufacturers a little more regulatory flexibility because they have the safety extra hurdles in place.

Since the development of lactate and diacetate to inhibit Listeria growth was commercialized, there have been many other ingredients introduced that have enlarged the array of choices for processors. These include blends of organic acid salts and other natural fermentation products, bacteriocins, phages, some

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Another reason for the widespread use of growth-inhibiting ingredients was the USDA rule issued on an interim basis in late 2003 and finalized in 2005.

It specified three regulatory options to
address L. monocytogenes risk for RTE
meat and poultry products. These can
be found in 9CFR430.4. The options ac-
knowledge the multiple hurdle mental-
ity, but the regulatory numbering system
is the opposite of the number of Listeria
hurdles. An Alternative 3 system relies
natural antioxidants and other ingredi-
ents. A list of approved substances with
their labeling requirements is found in
USDA – Food Safety and Inspection
Service’s (FSIS) directive 7120.1, which
can be accessed at
www.fsis.usda.gov/Regulations_&_
Policies/7000_Series-Processed_
Products/ index.asp.