Frank Busta

Where do microbiological criteria come from? It’s not unlike the question that is frequently answered with the birds and the bees story, except in this case it is usually adult professionals asking the question about microbiological control.

How are microbiological standards set? What is the scientific way to set guidelines, limits, or standards? Skeptics might speculate that they were someone’s guess, or perhaps that some “knowledgeable expert” group dreamt them up at a clandestine meeting. Maybe they were dictated by the Codex Alimentarius Commission, or were the result of a quantitative approach based on risk management.

Often we are not sure of the origin of existing criteria, but we should be able to know in the future. Obviously, an analytical, systematic scientific determination is preferred. The Food Safety Objective (FSO) approach coupled with the Hazard Analysis Critical Control Point (HACCP) approach offers that alternative of a transparent determination in risk management.

Recently proposed by the International Commission on Microbiological Specifications for Foods and on its way to acceptance by Codex Alimentarius, FSO is a statement of the maximum frequency and/or concentration of a microbial hazard in a food at the time of consumption that provides the appropriate level of protection. By using FSOs, goals for improving food safety can be translated into quantitative terms that both regulatory agencies and industry can use to control potential hazards.

FSOs integrate scientific data from risk assessment to designate quantifiable frequencies and concentrations that address specific public health demands. Under the FSO approach, the processor would know the level of hazard that is considered appropriate in the final product and would design the process to consider the initial number of pathogens and any subsequent growth after processing during storage, distribution, and preparation. The FSO defines the expected level of control that must be achieved to meet the appropriate level of consumer protection. Since the FSO is to be met at the time the consumer eats the product, an extremely important consideration is the control of any increase in concentration of pathogen or toxin after manufacture, i.e., during storage, distribution, sale, and preparation.

FSOs are met using Performance Criteria, which are the required outcome of one or a combination of control steps. At certain points in food processing, control measures can be applied to either prevent an unacceptable increase in a microbiological hazard or reduce the hazard to an acceptable level. Chilling cooked foods prevents the growth of pathogens (i.e., no increase of hazard), and pasteurization of fluid products eliminates enteric pathogens (i.e., decrease of hazard). These are frequently specified as orders of magnitude of control, e.g., populations of pathogens might be reduced 10- or 100- or 10,000-fold (1D, 2D, or 4D).

Performance Criteria are delivered with selected processes (e.g., heat) and specific parameters of the treatment (e.g., time, temperature, raw material quality, etc.). These processes and parameters are defined in measurable terms described as Process/Product Criteria. From the concurrent HACCP approach, the Critical Control Points are generally identified before establishing the Process/Product Criteria on which the HACCP Critical Limits are based. The remainder of the HACCP program follows from identifying critical limits through verification and record keeping. Only after the completion of the entire exercise can statistically relevant microbiological criteria be considered. The FSO approach will be successful when directly intertwined with a food processor’s good manufacturing practices and HACCP program.

Regulatory agencies can use FSOs to communicate the level of control expected in food processes and then to evaluate the adequacy of a facility’s control system. FSOs differ from the microbiological criteria that have been traditionally used to determine the acceptance of food products. Microbiological criteria specify details such as a sampling plan and the method of sample preparation and analysis, but the criteria cannot be readily used to evaluate a process. Microbiological testing of finished product provides a snapshot for the time the food was produced and may be useful in verification. However, review of the production of the same product’s food safety management system using an FSO approach coupled with an effective HACCP program would provide a more meaningful assessment of long-term control.

For more details about how FSOs fit into a framework for food safety management, see the recently released “IFT Expert Report on Emerging Microbiological Food Safety Issues: Implications for Control in the 21st Century” at

Professor Emeritus
University of Minnesota