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Several disease-causing microorganisms can survive in low-moisture foods and have been implicated in food recalls in recent years. Organisms, such as Salmonella in ready-to-eat foods and snacks, and E. coli and Listeria in dehydrated meats, can pose the potential for illness to consumers. Thus, it is the responsibility of the food producer to provide safe food by preventing pathogen presence or destroying those that have the potential to be present.

Low-moisture foods present some challenges. Pathogenic organisms exhibit greater resistance to heat in low-moisture foods than in moist foods. For example, while Salmonella can be destroyed in a moist food in a short time at temperatures of 160°F, the Guidelines for Validation of Dry Roasting Processes from the Almond Board of California states that Salmonella destruction in almonds takes more than 1.5 hours at 250°F.

Two vitally important components are needed to document process control for processors of low-moisture foods: (1) scientific data that states the required processing limits to achieve pathogen destruction; and (2) in-plant measurements to show the limits are met. The scientific data is part of the design phase of the HACCP/Food Safety Plan. The in-plant data is part of execution. Those two elements are at the heart of the validation and verification requirements of FDA and USDA.

SCIENTIFIC DATA IN DESIGN. The USDA document, FSIS Compliance Guideline HACCP Systems Validation, provides the following list of potential sources of scientific information:

  • Published processing guidelines.
  • Peer-reviewed scientific or technical data or information.
  • Processing authority expert advice.
  • A challenge or inoculated-pack study.
  • Pathogen modeling programs.
  • Data gathered in-plant.
  • Regulatory performance standards.
  • Best practice guidelines.

Each of these may be used to justify a food safety measure in a HACCP or Food Safety plan. But low-moisture food procesors may face the challenge of little scientific or technical data for their products. If that is the case, then a challenge or inoculated-pack study may be required. In such a study, a product is subjected to a treatment — such as a heat treatment or addition of an ingredient that inhibits the targeted microorganisms. After the treatment, the product is tested to see if the microorganisms have been reduced or eliminated. The final report from the study can be used to justify the safety of the food, when properly processed, and will describe the in-plant processing parameters used to control the microorganisms of concern for the product.

Let’s consider how a study could be conducted for beef jerky (USDA regulated) or a meat-containing pet treat (FDA regulated) produced in different facilities. Assume that each product has formulation control for beginning moisture, protein, fat content, and possibly the addition of preservatives. Ending moisture is specified.

For such a product, the design phase begins with a hazard analysis, including:

  1. Assemble the HACCP/Food Safety Plan team, with food safety experts.
  2. Describe the product.
  3. Identify its intended use.
  4. Construct a process flow diagram.
  5. Conduct on-site confirmation of the flow diagram.
  6. List potential hazards of each step.
  7. Conduct an analysis of hazard severity.
  8. Consider any measures to control identified hazards.

Imagine that each of the two products is processed in a drying oven, and that heat will be used to destroy the pathogens of concern. Oven time, temperature, and air flow settings are known.

So, how do we conduct the study? Perhaps in a microbiology laboratory, perhaps in the processing plant with a harmless surrogate microorganism. A useful article describing considerations for such a study, “Parameters for Determining Inoculated Pack/Challenge Study Protocols” by the National Advisory Committee on Microbiological Criteria for Foods, outlines aspects of study design, selection of experts to assist with studies, microbiological testing, and writing of a final report. Your report should explain the critical processing steps or conditions that are necessary to assure pathogen destruction or inhibition. Critical conditions could include process times, temperatures, humidity, pH, concentrations of ingredients or treatments, or other items relevant to the product and process.

THE EXECUTION PHASE. Data from the production plant is used to demonstrate that the process parameters can be consistently delivered using the specific equipment in the plant. This requires acquisition of facility data and confirmation that all the scientific parameters from the design phase are met. Both FDA and USDA’s Food Safety Inspection Service (FSIS) require that control points be validated in-plant.

FDA’s FSMA Preventive Control rules (21 CFR 117 for human food and 21 CFR 507 for animal feed) state that the first part of validation, the scientific justification, takes place prior to implementing a food safety plan, and the in-plant demonstration of capability should take place within 90 days of production start, or within another reasonable time frame as justified by the Preventive Controls Qualified Individual.

How is the in-plant work conducted for our example products? The FSIS Compliance Guideline for HACCP Systems Validation describes that plants should:

  • Implement the critical operational parameters in the production process consistent with the parameters in the scientific support;
  • Identify at least one product from each HACCP category for which to gather in-plant validation data;
  • Collect in-plant data demonstrating the effectiveness of the implementation of the critical operational parameters for at least one product from each HACCP category; and
  • Analyze the data to determine whether the critical operational parameters are being implemented effectively.

The report from the in-plant execution phase is kept with the scientific justification from the design phase. Reports are part of the food safety or HACCP plan. During the facility’s daily operation, in-process data is collected; operator observations of the process take place; and record review occurs, consistent with the design and execution requirements. When established limits are exceeded, corrective action occurs.

Validation is comprised of up-front design and in-plant execution for any food governed by FDA and USDA. Low-moisture foods can present special considerations beyond some other foods, due to the potential for increased microbial resistance to some treatments. With the scientific design and plant execution completed, food safety is maintained by adherence to defined process parameters.

The author is a senior science advisor, GMA, and contributing author of the forthcoming book, Control of Salmonella and Other Bacterial Pathogens in Low-Moisture Foods, edited by Richard Podolak and Darryl G. Black.