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Question 4. When microbial testing is an appropriate verification activity (for finished product), what considerations
should a company apply in selecting the test microorganism (e.g., specific pathogen or specific indicator organism) and
type of test (e.g., presence/absence or enumeration)? What are appropriate indicator microorganisms for verifying
that processes adequately control pathogens?
Finished product testing (lot control and/or process control) may be appropriate if there is a change in supplier, if there
is concern regarding an emerging issue, if environmental monitoring data demonstrate a trend or if other seasonality
considerations for the fruit/vegetable source change the risk profile of the starting material.
Question 5. What principles and criteria should a company apply in determining the frequency of testing finished
product to determine if the company's food safety system for that product is effective?
For criteria, refer to National Advisory Committee on Microbiological Criteria for Foods (2018) Response to Questions
Posed by the Department of Defense Regarding Microbiological Criteria as Indicators of Process Control or Insanitary
Conditions. Journal of Food Protection: January 2018, Vol. 81, No. 1, pp. 115-141.
Question 6: Are there situations in which testing at sites other than the end of the process can achieve the goal of
verifying the adequacy of control of microbial hazards?
Pre-harvest testing or testing at receipt at the processing facility may be considered, depending on commodity and/or
other risk assessment parameters. Activities associated with supplier verification, assays and/or electronic monitoring
of wash water systems must account for varying acidity; microbial susceptibility and spoilage; comingled lots; crosscontamination from slicing. If we can conduct field or pre-harvest testing, that would be one situation. There should
be a direct correlation, assuming that the environmental monitoring is demonstrating a trend and/or change that
demonstrates an increase in risk of contamination during the processing; verification activities could include zone 1
testing and/or process control type of testing application.
Question 7: What criteria should a company apply in determining that microbial testing results indicate a loss of
(systemic) process control? What actions should a company take if test results indicate a loss of control? When
verification testing indicates loss of process control, to what extent should verification testing be increased, how far
upstream and downstream should it go, and when and how should it be scaled back?
For end products, microbiological testing is not considered a primary means of routinely assessing product safety
and stability. Assessment of safety is best carried out through the environment, the processing line. Microbiological
testing can provide a supporting role here, to verify washing step process control, and can be reduced based on results
demonstrating that the process is well under control. If significant changes are introduced or if there is a failure in the
process control, then testing can be intensified temporarily, to verify that the process returns to being under control.
Figure 6. Criteria for design of a microbiological testing program for fresh-cut fruit.

CONCLUSIONS
When a hazard analysis identifies a hazard that requires a
preventive control, microbiological testing can help a food
manufacturer be confident that their manufacturing process
is capable of controlling pathogens (validation) and is actually doing so (verification). It also can be used to verify sanitation of the environment and for supply chain verification
activities. Microbiological testing for verification of controls
for hazards identified as requiring a preventive control is particularly important for RTE foods, which will not be cooked
before consumption.
Should your firm test finished products for pathogens? "It
depends" and "it's complicated." Although testing of finished
products can inform you that one of your preventive controls
is not working, it is not recommended for determining final
lot acceptance. Because the defect rate (i.e., the rate at which
pathogens are present in samples) is likely to be very low, it is
not feasible to sample enough of the lot to ensure that it is free
of pathogens.

It is not always the best strategy (and in some cases not
advisable) to test for your target pathogen. The use of surrogate organisms in the validation of preventive controls and
the use of indicator organisms to verify the effectiveness of
preventive and sanitation controls will likely provide more
useful information than pathogen testing. Use of a surrogate
organism allows validation work to be completed on the
same equipment and in the same facility in which manufacturing occurs. In addition, indicator testing is often quantitative and can help identify trends that inform process control
more quickly.
The goal of environmental monitoring for pathogens is to
seek and find them, not to fear positive samples. The only
way to eliminate contamination is to find it. New technology
(next-generation sequencing that can link illnesses to manufacturing facilities) and regulatory changes (increased enforcement actions) together provide strong incentives for a food
manufacturer to identify and fix environmental problems as
soon as possible.

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