What is the difference between critical and operational limits?


There are distinct differences between operational limits and critical limits. Both have a vital role to play in producing safe food. Establishing a critical limit at a critical control point is also a legal requirement.

Every critical control point will have a critical limit set for each control measure.  A critical limit is the third principle of HACCP and an absolute value that separates the acceptable (safe) from the unacceptable (unsafe) at an operational condition. It must be achievable, measurable, detectable in real time and related to the control measure. Criteria used to set critical limits include physical, chemical and sensory parameters. These include measurements of temperature, time, size, moisture level, pH, Aw, visual appearance and texture. Setting a microbiological critical limit for a critical control point is not practical because it relates to the hazard and not the control, and levels cannot be monitored on a timely basis. A failure to achieve a critical limit is called a deviation.

Critical limits must be validated. This requires the HACCP team to provide evidence to support a justification for a critical limit. Evidence to justify a critical limit can be a process where tests are conducted internally because data is not readily available or can be a review of information. Credible sources of information include scientific studies, regulatory or industry guidelines and expert knowledge. The findings on how critical limits were established and validated must be documented and available for review. This is important for three reasons: the HACCP team may need to benchmark current information against new data, justifications may be checked during audit or the validation study may be required to support a due diligence defence in court.

Operational limits are more stringent than critical limits and include target and action levels. A target level creates an area of tolerance before a critical limit is breached. This provides an opportunity to intervene before a deviation occurs at a critical limit. An action level is a 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.

Critical limits and operational limits must be communicated clearly to CCP monitors. This can happen during HACCP training and when limits are included in standard operating procedures and CCP monitoring records.

A review of critical and operational limits should happen when there is a significant change or new information becomes available (e.g. process, legislation, new scientific information, threat to safety, feedback from an audit).

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