Predict Safety

In a hazard analysis of the production of chicken cordon bleu, Salmonella associated with the raw chicken is a hazard reasonably likely to appear. During the preparation step, the raw chicken is exposed to temperatures up to 55°F (13.8°C) for less than four hours. Both the PMP and THERM estimate that less than 30% of lag phase duration will have elapsed during a four-hour period at this temperature. Further, if the lag phase duration is not considered, the time needed for Salmonella populations to increase by 0.3 log colony forming units (CFU)—one doubling or generation time—is greater than six hours at this temperature. Applying predictive microbiology in this example provides evidence that this step in the hazard analysis should not be regarded as a critical control point.

In establishing critical limits for a ready-to-eat (RTE) deli sandwich prepared ahead of time by hand, the question is what cold-holding temperature will allow a maximum eight-hour holding time before consumption that can be justified by scientific information rather than current regulatory guidance? The FDA’s Food Code allows for time only (four hours, no temperature control) as a public health control of RTE foods intended for immediate consumption. Since our RTE deli sandwich is prepared by hand, the microbial hazard most likely to occur is the transfer of S. aureus.

Using the PMP, we can determine a potential increase in S. aureus populations at an ambient temperature of 75°F (24°C) and no lag phase of about a 1.5 log CFU during the currently allowed four hours. If this population increase is acceptable based on existing guidance, then adjusting the cold-holding temperature to establish a longer storage time is possible. For example, we can obtain our eight-hour storage time by cold-holding our RTE deli sandwich at 67°F (19.5°C); if we cold hold at 60°F (15.5°C), we can stay below this potential level of S. aureus growth for up to 17 hours.

Temperature Abuse

Another potential application for predictive microbiology tools, only recently considered, is reducing economic losses associated with the condemnation of foods exposed to short-term temperature abuse due to refrigeration failure at retail and food service operations. Estimated losses to a large retail or food service company may be tens of thousands of dollars each year. Most often, condemnation results from mechanical refrigeration failure that allows the product temperature to rise above the 41ºF (5ºC) cold-holding requirement enforced by many regulatory authorities. The primary reference for this cold-holding requirement is the FDA’s Food Code.

Another criterion often linked to this cold-holding requirement is that exposure of potentially hazardous foods—raw meat and poultry, for example—to an out-of-temperature condition should not exceed four hours, although this is not specifically detailed in the section of the Food Code covering cold holding of potentially hazardous food. The four-hour limit likely comes from another section of the Food Code that addresses the use of time only as a public health control rather than in conjunction with temperature. This section, however, applies specifically to RTE foods or to a working supply of raw foods just before cooking, both of which are intended for immediate consumption. Thus, the criterion does not apply to situations such as refrigeration failures, in which raw meat and poultry have been exposed to temperatures above 41ºF (5ºC) for any period of time.

Because the Food Code is written in a manner that provides inflexible limits for regulatory control, it does not offer the deviation guidance required to make appropriate disposition decisions in these out-of-temperature situations. Recent research suggests that the four-hour limit commonly imposed may be unnecessarily conservative for raw meat and poultry products, especially at the lower end of the temperature range. Using a predictive microbiology tool such as THERM v.2 to more accurately predict pathogen behavior in raw meat and poultry could drastically reduce the economic losses associated with condemnation of these temperature-abused foods—without compromising consumer safety.