Critical limits

A critical limit is a criterion, observable or measurable, relating to a control measure at a CCP, which separates acceptability from unacceptability of the food. Put simply, it is the line between safe and unsafe. A failure to meet a critical limit is called a deviation.

Measurable limits use a number, such as temperature, time, pH or water activity. Observable limits are things you can see, such as a pump setting, conveyor belt speed, or ice covering a product. One step can have more than one limit. A heat treatment often needs both a temperature and a time.

The recitals to Regulation 852/2004 also say that a critical limit does not have to be a number in every case. What matters is that it is clear. Anyone doing the check must be able to say whether it has passed or failed. 'Cook until done' is not a critical limit. 'A core temperature of 75°C for 30 seconds' is.

Critical limits should be validated. That means there should be evidence that they can control the hazard. A business does not always need its own study. Limits can come from regulations, published science, guidance from the authorities, or studies by an equipment maker. The FSA gives these cooking equivalents: 75°C for 30 seconds, 80°C for 6 seconds, and 70°C for 2 minutes. If you use outside guidance, check that it fits your own food and process.

Some temperature rules differ between nations. In England, Wales and Northern Ireland, the legal maximum for chilled food is 8°C, with 5°C or below as the aim. In Scotland there is no fixed number in law. Food must be kept in a fridge or a cool ventilated place, and Food Standards Scotland recommends 5°C or below.

For hot holding, the rule is 63°C or above in England, Wales and Northern Ireland, and above 63°C in Scotland. For reheating, food in England, Wales and Northern Ireland should be piping hot throughout, and 75°C at the core is the common guide. In Scotland the law says at least 82°C, unless this would harm the quality of the food.

Many businesses also set a target that is stricter than the critical limit. A fridge may have a target of 5°C and a limit of 8°C. The target gives an early warning, so that you can act before the limit is reached. Going past a target calls for an adjustment. Going past a critical limit is a deviation, and it means the food may be unsafe.