Once the critical control points have been identified, staff need to know exactly when each one is under control. That is the job of the critical limit.

In this module you will learn what a critical limit is, see common examples, and learn where limits come from and how they are set.

A critical limit is the value that separates safe from unsafe at a critical control point. If the limit is met, the step is under control. If it is not, the food may be unsafe.

Critical limits must be measurable or observable, so that staff can check them quickly and clearly. They are usually based on temperature, time, acidity, water activity or a visual check, for example that a metal detector rejects a test piece.

• Cooking: a core temperature of at least 75°C, or an equivalent time and temperature combination.
• Chilled storage: 5°C or below.
• Hot holding: 63°C or above.
• Reheating: until piping hot throughout, with a core temperature of at least 70°C for two minutes, or an equivalent.
• Pasteurising milk: at least 72°C for 15 seconds.
• Metal detection: the test pieces must be detected and rejected at every check.

Critical limits must be based on reliable evidence, such as:

• Food law, which sets some temperatures directly.
• Official guidance, for example from the Food Safety Authority of Ireland.
• Industry guides and codes of practice.
• Scientific studies, and advice from experts.
• Equipment manufacturers’ instructions.

A limit that is simply guessed cannot be relied on.

Many businesses also set a target level, or operating limit, that is stricter than the critical limit. For example:

• Critical limit for a fridge: 5°C. Target level: 3°C.
• If the fridge reaches 4°C, staff can adjust it before the critical limit is broken.

This gives an early warning, so that problems can be corrected before any food becomes unsafe.