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• 15. Process Verification

15. Process Verification

Most processing operations will have listeriocidal step, i.e. is, a step in the process that is designed to eliminate, or at least significantly reduce, the total number of contaminating bacteria, e.g., heat treatment. The operating criteria will need to be established for each listeriocidal step.

How well so you know your process?

The following set of questions should be used as a guide. It will be necessary for each business to identify the process steps where some form of control over Listeria can be established, and then to ensure that effective control is always maintained at these steps.

• Do you have a listeriocidal step(s) in your process?

For example, heat treatment.

• What is the required time/temperature combination?
• How do you know that this is a satisfactory listeriocidal step?
• How can you verify that this time/temperature combination is achieved all the time?
• What is the frequency of checking?
• Do you have records of this check?
• What is the heat source?
• Is the heat even?
• What can you do if you lose heat?
• Is your product protected by acid?
• What pH do you consider suitable to prevent the growth of Listeria?

(See the note on pH in the section on Growth Characteristics of Listeria).

• What controls for you have in place to ensure that the correct pH is maintained?

All process steps designed to control Listeria should be documented, verified and checked regularly.