Pathogen Reduction Dialogue Panel 3 Microbial Testing for Control Verification

1. Pathogen Reduction Dialogue Panel 3 Microbial Testing for Control Verification Robert L. Buchanan U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition May 7, 2002

2. Microbiological Testing • Microbiological testing important food safety tool • Technologically-based, statistically-based tool • Right tool for the right job

3. Microbiological Testing • One of the most apparent, but poorly understood parts of food microbiology • Different types of microbiological testing • Safety of “batches” * • Process control * • Investigational sampling • Surveillance

4. Microbiological Testing • Effective use requires a clear understanding of the goals, assumptions, and characteristics of testing programs

5. Microbiological Testing • “Within batch testing” vs. “Between batch testing” • Different goals, assumptions, and techniques

6. Microbiological Testing • “Within Batch Testing”:Demonstrate the safety of a single lot of food

7. Microbiological Testing • Within-batch testing • detailed “snapshot” of an operation • assumes no prior knowledge of the process • focus on establishing safety (or quality) of the batch • provides only limited capability to do trend analysis of performance over time • can be used nationally to acquire “state of industry”

8. Microbiological Testing • Effective within certain ranges of contamination frequency or levels of contamination • Above or below those ranges, becomes increasingly ineffective • When acceptable defect rate is less than 1%, the number of samples needed becomes a limiting factor

9. Microbiological Testing • “Between Batch Testing”: Demonstrate that a food safety system/process is continuing to function as intended

10. Microbiological Testing • “Between-batch testing” • not designed to assure batch safety which is assumed to be safe if validated process is “in control” • assumes intimate knowledge of process • requires prior analysis for performance and variation • requires sampling over time • can also be used nationally to assess “state of industry”

11. Microbiological Testing • “Between-batch testing” • Much easier to demonstrate that a process is not functioning within a specification than to prove that something (e.g., a pathogen) is not present

12. Sampling for Process Verification • Microbiological contamination typically flows with a process • A microbiological sample taken within a process provides a measure that integrates all the preceding steps in a process

13. Sampling for Process Verification • The status of a multiple step process is the summation the initial level of contamination and all the steps that increase or decrease the level of contamination Microbial Status = Ho + I + R

14. Sampling for Process Verification • Sampling of end products integrates the effects of the entire food safety system • For investigations of cause, benefits to taking samples at multiple locations

15. Process Control Statistics • The basis for process control evaluations is the collection of microbiological data over time • Typically arrayed graphically as a control chart

16. Process Control Statistics • First step is to conduct aprocess control study (baseline study) • An “under control” process is run for a period of time to access its “capabilities” and establish: • Central tendency (mean or median performance) • Variance • Also used to establish limits (control values) • Often use 3

17. Process Control Statistics • Loss of process control is then assessed by determining if “defect rate” has become greater than what would be expected by “chance alone” • Approach can be used with either “variables” (quantitative data) or “attribute” (+/- or binned quantitative data) sampling plans

18. + - + - - - - + - - - - - + - - Example: Moving Window Sum • One of simplest for attribute sampling plans

19. Moving Window Sum Example: Making red marbles Receive Blue Marbles Paint Marbles Red* Package Marbles *Defect rate = 10%

20. Moving Window Sum • Based on the probability of finding more than an expected number of “defective” responses within a specified window of samples

21. Moving Window Sum Is this process under control? (Sampling rate = 1 per 1000)

22. Moving Window Sum When is control of this process lost? (Sampling rate = 1 per 1000)

23. Impact of Stringency

24. JuiceHACCP

25. Juice HACCP • Key feature: • 5-D (99.999%) performance standard • Restricted to juice after it has been expressed • Verification of this requirement is via process validation and review of process records • Goal: Limit risk to >10-5/year

26. Juice HACCP • Microbiological testing not required based on • ineffectiveness of testing at low defect rates • treatment affects all juice • processes are validated and reliable

27. Microbiological Testing • Simplified example • Assume 1 enteric bacteria per ml • 5-D treatment reduces to 1 per 10,000 mL • To detect survivor, need • 1 10-L sample • 10 1-L samples • 100 100-mL samples • 1000 10-mL samples • 10,000 1-mL samples

28. Juice HACCP • Key exemption: Citrus Juices • Processors of citrus juices may count surface treatments of the fruit as partially or totally fulfilling 5-D treatment • Based on the underlying assumption that the nature of citrus fruit is such that contamination is restricted to the fruit’s surface

29. Juice HACCP • These citrus juice processors have an additional HACCP verification requirement of periodic testing for E. coli • Two 10-ml juice samples/1000 gal/day • Once per week if produce <1000 gal

30. Juice HACCP • Data evaluated using process control statistics using a 7-sample window • One positive sample requires process review • Two positive samples require diversion to 5-D after extraction until cause identified

31. Juice HACCP • Designed to verify that the original assumption is still valid, i.e. pathogens are restricted to the surface of the fruit • Internalized pathogens will not be treated • Potential for growth at least in some fruit • Within range for effective detection • Requirement takes into account potential for chance contamination

32. Microbiological Testing • Microbiological testing can be an integral part of any integrated program for verifying the effectiveness of food safety control measures