Tag Archives: food safety testing

Purnendu C. Vasavada, Ph.D., Professor Emeritus at University of Wisconsin

What Should You Know About Food Safety Testing?

By Sangita Viswanathan
No Comments
Purnendu C. Vasavada, Ph.D., Professor Emeritus at University of Wisconsin

Food safety is in the news. Recent food industry, regulatory and consumer trends stress proactive, systematic and preventive approach to food safety by managing food hazards and risks. Testing for food safety hazards, particularly microbial hazards and allergens throughout the food production and processing chain is becoming increasingly important in assuring food safety. Food testing is also becoming important for detection of adulteration.

In next week’s Food Safety Consortium to be held in Schaumburg, IL, Purnendu C. Vasavada, Ph.D., Professor Emeritus at University of Wisconsin, River Falls, and President of PCV & Associates, LLC, will discuss trends in the food safety testing market and approaches for testing of food and food plant environment, emphasizing microbial and other significant food hazards. In this article, PC, as he is popularly referred to, gives a sneak-peek into his presentation.

Food Safety Tech (FST): You will be speaking about the Food Testing Market – what are some broad trends that you are seeing?

PC: Food Microbiology testing is increasing worldwide but majority of testing is still dealing with food quality assurance and ingredient and product testing. Testing for pathogens seem to be driven by regulatory requirement. According to recent market reports, 76 percent of test volume in North America is for routine microbiology. In the EU and Asia, routine microbiology accounts for 81 percent and 72 percent of test volume, respectively.

Most pathogen testing is for Salmonella, E. Coli 057:H7 and Stex, Listeria and as L. monocytogenes. There is an increasing interest in testing for Campylobacter.

Testing of in-process and environmental samples is more common in NA and Europe. In Asia in-process/environmental testing only accounts for 9 percent of total test volume.

FST: In your presentation at the Consortium, what will you talk about FSMA and its impact on food safety testing?

PC: I plan to include a brief discussion on testing as related to monitoring and verification of Preventive Controls.

FST: Where is food safety testing headed, and what should food safety managers keep in mind?

PC: Given the emphasis on supply chain management and process control to manage identified hazards in preventive mode, food safety managers should understand testing internal and external testing requirements and complexity of sampling, testing tools and approaches not simply focus on cost aspects. Even if testing is outsourced, becoming familiar with various methods and testing tools will be necessary.

FST: Who should attend your presentation and why?

PC: Plant managers, quality assurance supervisors, marketing managers, food safety testing methods, equipment and service providers as well as anyone interested in food safety testing would find this presentation very useful and relevant to their day-to-day activities.

Are you registered for the Food Safety Consortium yet? Sign up now, and hear from over 70 experts in this area.

Thomas R. Weschler, Founder and President, Strategic Consulting, Inc (SCI)

High False Positive Rates for Pathogen Food Safety Testing

By Thomas R. Weschler
No Comments
Thomas R. Weschler, Founder and President, Strategic Consulting, Inc (SCI)

This article looks at proficiency testing (PT) for pathogen analysis, and the recent finding by the the American Proficiency Institute (API) of a 6.6 percent false-negative rate on food safety PT samples (14-year average for the 1999-2012 period).

While at IAFP this year, I met with Heather Jordan, who directs food PT programs at API. The proficiency testing programs are used at many food labs in conjunction with lab accreditation programs. Proficiency testing is done at food plant labs (FPLs) and corporate labs, as well as at food contract testing labs (FCLs) as a way to demonstrate quality results in their food micro and chemistry testing.

More proficiency testing but less proficiency?

In fact, the use of PTs is increasing in food labs, which is probably tied in part to the push for lab accreditation by FSMA and non-government groups like GFSI. Yet it seems to me that the current use of PTs doesn’t go far enough to enable an FPL or FCL to demonstrate overall laboratory competency, and gain or maintain accreditation (ISO 17025).

In most labs, PTs are done just a few times a year. And really, they test the competency of the lab technician and protocols used in analyzing the PT samples. They are not a holistic measure of the lab and its ability to consistently generate quality results on every test run by every operator in the lab.

In a previous life I ran a group of environmental testing labs, which also are required to run PT samples during the year. From this experience, I know that lab personnel are aware that PTs are in-house: The sample-receiving group logs them in, and then alerts management. As a result, the best operators usually are assigned to run the PTs. This kid-glove treatment is not representative of day-to-day practices and processes. If we really want to validate and accredit the proficiency of an entire lab, shouldn’t every operator be tested on all protocols in use?

Plus, if labs know when they are running PT samples, and likely have their best operators running them, shouldn’t there be few, if any, false-negative or false-positive results? Surprisingly, that’s not what the API research found…

API study: Performance accuracy for food pathogens remains problematic

In a retrospective study, “Pathogen Detection in Food Microbiology Laboratories: An Analysis of Proficiency Test Performance,” API analyzed the results from 39,500 food proficiency tests conducted between 1999 and 2012 to see how U.S. labs are doing in detecting or ruling out contamination of four common food pathogens.

Over the 14-year period, “False negative results ranged from 3.3 percent to 14.0 percent for E. coli O157:H7; 1.9 percent to 10.6 percent for Salmonella spp; 3.4 percent to 11.0 percent for L. monocytogenes; and 0 percent to 19.8 percent for Campylobacter spp.” Most concerning is that while both false positive and false negative rates were down in the last year of the study, the cumulative false negative rate for the 14-year period was 6.6 percent.

As we know, false positive results (in which a sample that does not contain pathogens is incorrectly shown as positive) are a nuisance. But false negative test results—which fail to detect true pathogenic organisms in the sample—are not unacceptable.

Tom-Weschler-False-Negatives-Sep-2014

The cumulative average false positive rate was 3.1 percent, less than half of the false negative rate for the same period.

The objective of the study—and, I would think, of proficiency testing in general—is to demonstrate improvement in lab performance year over year. The results of the API report concluded to the contrary, however: “Performance accuracy for food pathogens remains problematic with the recent cumulative trend showing a slight decrease for false positive and false negative results.”

Clearly if false negatives happen in proficiency programs, they happen in the course of regular testing at food labs. I’m told that many FCLs and FPLs rely on other parts of their QA systems to make sure testing is being conducted properly. Even so, the documentation of ongoing and unacceptably high false negative rates in PT testing is a big concern for everyone. It also points to a number of follow-on questions:

  • Would the false negative and false positive results be even higher if every technician, rather than the best operator, performed the analysis?
  • PT samples are created in only a couple of sample matrices. Would results be even worse if performed on the myriad of sample matrices present in the food industry?
  • What are the performance results among all of the pathogen methods available? Are some methods better than others when measured in real world conditions? Do the more complex protocols of some pathogen diagnostic systems result in poorer PT performance results?
  • Would PT results and, even more important, lab proficiency improve if the frequency of PTs increased, and were required of every technician involved with real food samples?
  • How can proficiency testing be used to isolate problem areas, whether in the pathogen diagnostic method or the competency of lab operators and processes?
  • And finally, is the performance data different between food contract labs and food plant labs? And are all FCLs are equal, or are some more able to deliver quality results?