What is a Critical Limit?
The HACCP team must establish a critical limit(s) for a selected control measure at each critical control point (CCP) to ensure it is operating as expected. Codex defines a critical limit as “a criterion which separates acceptability from unacceptability”1. A “failure to meet a critical limit” is called a deviation1.
A critical limit is an absolute value (minimum or maximum), not a range. It must be achievable, detectable during processing and relate back to the control measure. Parameters for critical limits maybe chemical, physical or even procedural2. Criterion often used include time, temperature, pH, Aw, moisture content, size, etc. Setting a microbiological critical limit is not practical because it normally involves a lengthy time delay2.
What is a Target Level?
A target level is more stringent than a critical limit. The difference between both values is called a tolerance. This buffer provides an opportunity to intervene before a deviation can occur at a critical limit. An action level is another measurable point between a target level and critical limit where appropriate action taken to bring the process under control. For example: a target level for cooking a product could be 78OC with a critical limit of 75OC and action level at 76OC to bring the process back under control.
Validate and Document Critical Limits
A critical limit must be validated. This requires reputable evidence to demonstrate it is achievable and can control the hazard to an acceptable level. Critical limits are often established by referencing validated literature including peer-reviewed scientific journals and regulatory or industry guidelines. If no published evidence exists it will be necessary to conduct relevant validation exercises, such as mathematical modelling, challenge testing using a surrogate microorganism, etc. Onsite trials may also be required to demonstrate critical limits are achievable and reproducible within product and process variables.
Evidence for the validation of critical limits must be documented to demonstrate they are based on reputable sources of scientific and technical data. This information could be checked during an audit or be required to support a due diligence defence in court. A documented validation study may include or reference target hazard, product description, process step, experimental approach, results, conclusions, recommendations, and contributors.
- Food and Agriculture Organisation of the United Nations (unknown). Section 3 – THE HAZARD ANALYSIS AND CRITICAL CONTROL POINT (HACCP) SYSTEM [online]. Available at: http://www.fao.org/3/w8088e/w8088e05.htm#module%2010%20%20%20establish%20corrective%20actions%20%20%20task%2010principle%205 Accessed on 01/11/20
- Food Standards Agency (2020). [Online]. Available at: https://myhaccp.food.gov.uk/ Accessed on 01/11/20