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2007-2009 Subcommittee: Parameters for Inoculated Pack/Challenge Study Protocols
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Subcommittee Members
- Dr. Donald Zink, Working Group Chair
- Dr. Gary Ades
- Dr. Scott Brooks
- Dr. Daniel Engeljohn
- Dr. Timothy Freier
- Mr. Spencer Garrett
- Dr. Kathleen Glass
- Dr. Linda Harris
- Dr. Michael Jahncke
- Dr. Joseph Madden
- Dr. Donald Schaffner
- Ms. Jenny Scott
Background
The restaurant and retail food store industry, totaling nearly 1.5 million establishments in the U.S. and their
suppliers, routinely uses inoculation/challenge testing to determine whether a specific food requires
time-temperature control for safety (TCS). A food establishment, including restaurants, retail food stores,
delis, caterers, and institutions or vending commissaries that provide food directly to the consumer, is
defined in the Food and Drug Administration (FDA) Food Code.
When laboratory testing is used to support a change in how the product is handled in a food establishment (e.g.,
refrigerated to unrefrigerated holding, extending shelf life, increasing ambient temperature storage or eliminating
the need for date marking), this data is submitted to a state or local regulatory agency or directly to the
FDA in the form of a variance application for approval. Food establishments or manufacturers submitting
this laboratory data to support their proposals must ensure the study is appropriate for the food and pathogen
of concern and incorporates the necessary elements into the study to yield a valid design and conclusion.
A variance from any provision in the FDA Food Code must also show that no health hazard will result from the
modification or waiver and product handling is under control using a HACCP plan. Examples of foods in which the
need for TCS was questioned include puff pastries with savory meat, cheese or vegetable fillings; churros
(fried dough) batter held unrefrigerated; sliced pasteurized processed cheese held at ambient temperature for
more than 4 hours; certain cheeses held unrefrigerated; etc. State and local regulators who evaluate a variance
application based on this laboratory evidence need criteria to help them determine whether the study was adequately
designed and whether the conclusions are valid.
The definition of potentially hazardous food (PHF) or time/temperature control for safety food (TCS food) was
amended in the 2005 FDA Food Code to include pH and aw interaction tables, allowing the hurdle concept to be used
in the determination of whether TCS is necessary or not (Chapter 1 Definitions, 2005 FDA Food Code, available at
https://webarchive.library.unt.edu/eot2008/20080923063147/http://www.cfsan.fda.gov/~dms/fc05-toc.html).
The two interaction tables as well as a decision making framework were developed by the Institute of Food
Technologists (IFT) and provided to FDA in the report, "Definition and Evaluation of Potentially Hazardous Food,"
December 31, 2001, IFT/FDA Contract No. 223-98-2333, Task Order No. 4 (available at
https://webarchive.library.unt.edu/eot2008/20080923063147/http://www.cfsan.fda.gov/~comm/ift4-toc.html).
When the pH and aw Interaction Tables and the decision making framework are insufficient to show that
a food does not require TCS, further product assessment using inoculation/challenge testing is likely required.
The IFT Report with its recommendations to FDA left a number of unanswered questions regarding the understanding and
implementation of a product assessment when pH and aw are unable to determine if TCS is required.
This was confirmed in a survey of stakeholders (attached) conducted by the Conference for Food Protection (CFP) in 2005.
Charge to the Subcommittee
Because of the many questions raised by regulatory and industry users on the definition of potentially hazardous
food (PHF) or time/temperature control for safety food (TCS food), the National Advisory Committee on Microbiological
Criteria for Foods (NACMCF) is asked for its guidance to clarify these issues.
- What are the appropriate criteria that must be considered for an inoculated pack/challenge study to determine if a food requires time/temperature control for safety (TCS)? For example, pathogen species/strain selection, use of surrogate organism, number of pathogen strains, inoculation level(s), incubation temperature(s), length of incubation/duration of study, food product physical properties, etc.
- What are the appropriate uses of mathematical growth and inactivation models? Under what conditions can these models be used as a substitute for inoculated pack/challenge studies? Of the models currently available, which one(s) are most suitable for use and what are the limitations of these models?
- What are the limitations for applying the results of an inoculated pack/challenge study on one food to another similar food?
- If the existing inoculated pack/challenge study protocols, e.g., those published by the American Baking Association, NSF International, and others, which are most suitable for application to a wide variety of foods and what are the limitations of these protocols? Are there existing protocols that are appropriate for specific food/pathogen pairs?
- Develop a decision tree to aid in the design of an appropriate inoculated pack/challenge study. Test or "desk check" the decision tree using the following five foods: meat filled puff pastry, (baked) cheese pizza, chopped lettuce, cheese (blocks or slices), and lemon meringue pie.
- Identify the basic knowledge, skills, education, training, experience, and abilities necessary for a multidisciplinary work group or individual to be qualified to design, conduct and evaluate an inoculated pack/challenge study and the pursuant results.
Summary of Subcommittee Meeting, May 21-22, 2008
- The Subcommittee met from May 21-22, 2008 in Washington, DC.
- The Subcommittee has developed a solid working draft document which provides background information
on appropriate criteria to consider for an inoculated pack/challenge study.
- The Subcommittee addressed issues related to appropriate challenge microorganisms, inoculation methods,
inoculum levels, storage conditions, sampling, and laboratory analysis.
- Work assignments were distributed to Subcommittee members.
- The Subcommittee will meet again on August 18-20 to continue work on the document. The next draft
will be circulated to the Subcommittee members prior to the August meeting.
Summary of Subcommittee Meeting, Aug 18-20, 2008
- The Subcommittee met from August 18-20, 2008 in Washington, DC.
- The Subcommittee has developed a near final draft document which provides background information
on appropriate criteria to consider for an inoculated pack/challenge study.
- The Subcommittee addressed issues related to appropriate challenge microorganisms, inoculation methods,
inoculum levels, storage conditions, sampling, and laboratory analysis.
- The Subcommittee drafted example decision questionnaires for several food products to check the applicability
of the designed approach for conducting microbiological challenge studies.
- The document will be finalized in an upcoming web meeting prior to the September plenary meeting.
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Last Modified:
August 21, 2008 |
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