• Different controls and processing methods

  • What approach should you use?

  • Guidelines for picking a validation program

Food processors help ensure the safety and quality of our food supply by implementing a number of controls and processing methods. Food processing techniques include thermal treatments such as pasteurization, and non-thermal applications such as high-pressure processing (HPP), UV, or chemical interventions. The effectiveness of these processes is verified through well-designed and executed process validation studies that may be conducted in the laboratory (i.e., a benchtop study) or in the processing plant.

What Approach Should You Use?

When a process can be simulated in the lab, a benchtop study is appropriate, with the primary advantage being that the target microorganism(s) can be used in the study. Alternatively, an in-plant study may be a better fit if the organism of concern cannot be used. For in-plant validations, a qualified surrogate organism is selected to represent the pathogen(s) of concern, often Salmonella spp. or  Listeria monocytogenes. A non-pathogenic surrogate is used to protect the plant processing environment and finished product from contamination with disease-causing microorganisms and should be equally or more resistant to the process applied when compared with the pathogen of concern. There are pros and cons to both approaches, but some guidelines can help determine whether validation using a surrogate organism is the best fit:

1. What is being validated – the process or the equipment?

Most times, the need for validation is to confirm that the specific processing parameters (exposure time and temperature/pressure/dose) are sufficient to inactivate the pathogen of concern. The objective is to validate the controls for the process, not to validate the equipment itself.

If, however, the intention is to evaluate the performance of the processing equipment, an in-plant study would be appropriate and the product would be inoculated with a surrogate organism for testing within the typical processing environment.

2. Can the process be simulated in a laboratory environment?

When validating a process, the lab will need to determine if it can be simulated in the lab. A common example of a laboratory validation study is for thermal treatment when the parameters that need to be validated are holding time and temperature. A benchtop study is also used to determine thermal death time and establish D and z values for a particular organism in a particular product – a useful tool for calculating different time and temperature combinations needed to achieve the desired lethality.

Processes with conditions that cannot be simulated in the lab, such as extrusion (which occurs under pressure) or irradiation are good candidates for a surrogate study.

3. If the process cannot be simulated in a lab, can pilot-scale equipment be used?

Processors may have a pilot-scale version of the production processing equipment. Validation using a pathogen may be acceptable if the equipment is completely separated from the production environment and does not need to remain free from pathogen exposure. If this is not the case, the laboratory would recommend the use of a surrogate and help decide whether the validation study should be performed on the pilot or production equipment.

4. The process has been validated, how do I ensure consistent results?

As a follow up to validating a process, even when laboratory studies were applicable, a processor may wish to understand whether they consistently achieve the lethality observed in the benchtop study. Variables such as fluctuation in the processing parameters or variability based on the location of the product in the equipment can be evaluated in subsequent in-plant studies using a surrogate organism. This is also a useful approach to understand if or how batch sizes, product depth, and other variables affect lethality.

When an in-plant study is the validation approach selected, the surrogate organism is grown and prepared in a controlled laboratory environment. The culture may be used to inoculate the product in the laboratory or the culture may be directly shipped to the processor for inoculation on-site, with or without the assistance of our experienced consultants. Inoculated product is enumerated for surrogate levels before and after the process is applied in order to calculate the process lethality or log reduction.

What can Mérieux NutriSciences do for you?

With years of process validation experience, the Merieux NutriSciences’ Food Science Center can help determine whether a surrogate study is the right fit for validating your process. Contact us today to learn more!

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