HACCP and Temperatures: When to Calibrate Thermometers and Keep Records

Controlling food temperatures is one of the most important tasks within a food safety system. However, a common question arises in restaurants, hotels, supermarkets and other food businesses: is measuring the temperature enough, or do thermometers need to be calibrated and records maintained?

A technical clarification made available by ASAE and published by Portugal's Directorate-General for Food and Veterinary Affairs (DGAV) helps clarify this issue. Technical Clarification No. 4/DGAV/2025 addresses temperature control in foodstuffs, the use of automatic recording devices, equipment calibration and legal metrological control.

For food businesses, the main conclusion is straightforward: simply having a thermometer is not enough. Businesses must ensure that the temperature-control procedures defined within their HACCP system are appropriate, that the equipment provides reliable measurements and that the necessary records can demonstrate that food has been kept under safe conditions.

Why Is Food Temperature Control So Important?

Maintaining the cold chain is essential for the safety of many food products. Inappropriate temperatures can encourage the growth of microorganisms and compromise both the safety and quality of food.

Regulation (EC) No. 852/2004 establishes that food business operators are responsible for food safety and specifically highlights the importance of maintaining the cold chain for products that cannot be safely stored at ambient temperature.

For this reason, temperature control should form an integral part of a business's food safety procedures.

Depending on the activity and the risk identified, temperature measurement may form part of a prerequisite programme, an operational prerequisite programme or even a Critical Control Point (CCP).

If you would like to review the fundamental principles of temperature control in food service businesses, see our article on temperature control in refrigerators and cold equipment in restaurants.

Is Automatic Temperature Recording Always Mandatory?

No. This is one of the important points clarified in the technical guidance.

Legislation requires automatic temperature recording in certain specific circumstances. Examples identified by the DGAV include the transport and storage of quick-frozen foodstuffs, subject to certain legal exceptions, as well as specific situations involving frozen fishery products and the transport of meat that has not been fully chilled.

This means that a restaurant does not necessarily have to install automatic recording systems in every refrigerator simply because refrigeration equipment is being used.

However, this does not mean temperature control can be ignored.

The DGAV clarifies that even where there is no specific legal requirement to use an automatic recorder, such equipment may still be necessary whenever temperature control is essential to food safety or has been identified as critical within the HACCP system.

When Might Automatic Temperature Recording Be Necessary?

The technical clarification provides several examples of situations in which the DGAV considers automatic temperature recording necessary, including:

Food freezing tunnels;
Temperature-controlled food storage chambers;
Food handling areas requiring controlled temperatures;
Receiving or dispatch areas involving temporary storage;
Certain types of food transport;
Production stages where temperature has been identified as a Critical Control Point;
Certain situations involving the extended storage of fresh fishery products.

The key issue is therefore the risk associated with the process. A HACCP system should identify where temperature control is necessary and define how that control will be carried out.

Do Thermometers and Recorders Need to Be Calibrated?

There is an important distinction between legal metrological control and calibration.

Legal metrological control applies to instruments covered by specific legislation, including certain automatic recording devices used in the transport and storage of quick-frozen foodstuffs.

Calibration, on the other hand, involves comparing a measuring instrument against a known reference to verify whether it is providing accurate measurements.

According to the DGAV clarification, calibration of thermometers and temperature recorders is not, in itself, a general legal requirement applicable to every piece of equipment used by every food business.

However, where temperature measurement forms part of the HACCP plan as a prerequisite, operational prerequisite or Critical Control Point, the reliability of that measurement must be ensured.

In these situations, equipment calibration becomes particularly important because a thermometer displaying an incorrect temperature can create a false sense of security.

Can a Thermometer Give an Incorrect Reading?

Yes. Like any measuring instrument, a thermometer can lose accuracy over time due to regular use, impacts, environmental conditions or deterioration of the equipment itself.

For example, imagine that a thermometer displays 4 °C when the actual temperature is significantly higher. The records may appear correct, while the food is in fact being stored outside the conditions defined by the food safety system.

For this reason, simply completing temperature-record sheets is not enough. Businesses must also have confidence in the measurement being recorded.

The DGAV indicates that calibration should ensure reliable and traceable results and also refers to accuracy-verification procedures that may apply to thermometers in certain circumstances.

Which Temperature Records Should Be Kept?

The records required depend on the type of activity, the equipment being used and the HACCP system itself.

In situations specifically covered by Regulation (EC) No. 37/2005 concerning quick-frozen foodstuffs, temperature records must be dated and retained by the food business operator for at least one year, or for longer where appropriate depending on the nature and shelf life of the products concerned.

In other situations, the relevant procedures and retention periods should be defined appropriately within the business's food safety system.

The important point is that records should be:

Reliable;
Legible;
Consistent;
Linked to the correct equipment or process;
Verifiable;
Retained for the period defined within the system.

Recording values simply to “complete the sheet” is not the purpose of HACCP. Records should demonstrate that monitoring has genuinely taken place and allow deviations to be identified and corrected.

What Happens When the Temperature Is Outside the Defined Limit?

One of the fundamental characteristics of HACCP is that a deviation should trigger a response.

If a temperature exceeds a limit defined within the system, the operator should assess the situation and apply the established corrective actions. Depending on the circumstances, this may involve checking the equipment, transferring food to another unit, assessing how long the deviation lasted or determining whether a particular food product remains safe.

This is precisely why records are important: they make it possible to identify trends and demonstrate what happened before, during and after an abnormal situation.

Learn more about Prevenção Ativa's HACCP and Food Safety implementation and support services.

The Common Mistake: Keeping Records Without Verifying the System

A restaurant may complete temperature records every day and still have an ineffective food safety system.

Some of the questions that should be reviewed regularly include:

Is the equipment measuring accurately?
Are the limits defined in the HACCP plan still appropriate?
Do employees know where and how to measure temperatures?
Do the records genuinely correspond to the measurements taken?
Are corrective actions defined for situations where limits are exceeded?
Have new pieces of equipment been incorporated into the HACCP system?
Has the documentation been updated to reflect changes made within the establishment?

This is precisely the type of verification that makes regular HACCP audits valuable. The purpose is not simply to confirm that documentation exists, but to verify that the procedures described actually reflect day-to-day operations.

Staff Training Is Also Part of Prevention

Even a technically well-designed system can fail if employees do not understand the procedures they are expected to follow.

Anyone responsible for taking measurements should know how to use the equipment correctly, recognise abnormal values and understand what action to take when a deviation occurs.

Regular training helps ensure that HACCP remains an operational system rather than simply a collection of documents stored in a folder.

Prevenção Ativa also provides Professional HACCP and Food Safety Training in the Algarve, tailored to the needs of businesses operating within the food sector.

What Should Restaurants Do Now?

The technical clarification does not mean that every restaurant needs to immediately replace its thermometers or install automatic recording devices in every piece of refrigeration equipment.

It does mean, however, that businesses should verify whether their existing system is appropriate.

A practical review should confirm:

Where temperature needs to be controlled;
What type of equipment is used at each monitoring point;
Whether manual or automatic recording is required;
Whether the instruments provide reliable measurements;
How the accuracy of the equipment is verified or assured;
Which records are retained;
Which corrective actions are defined for deviations.

Within an effective HACCP system, all of these elements should work together. Measuring, recording, verifying and correcting are all part of the same preventive process.

The updated technical guidance reinforces an essential principle: a temperature record is only meaningful if the measurement on which it is based is reliable.

For restaurants and other food businesses, the objective should not be to accumulate record sheets, but to ensure that the HACCP system effectively controls temperature-related food safety risks.

Reviewing procedures, verifying instrument accuracy, training employees and carrying out regular audits are all measures that can help identify problems before they compromise food safety.

Prevenção Ativa supports businesses throughout the Algarve with HACCP implementation, system reviews, food safety audits and professional training, helping to turn technical requirements into practical procedures that can be applied in daily operations.

Sources

This article is provided for general information purposes and is based on the DGAV technical clarification made available by ASAE and the legislation applicable at the date of publication. The application of specific requirements should be assessed according to the activities and processes of each individual food business operator.