Interlaboratory Tests. An Endorsement for the Food Industry

Interlaboratory Tests. An Endorsement for the Food Industry

Today’s society is increasingly aware of the two most significant aspects of food control: Quality and Food Safety and Hygiene.

At the European level, there is comprehensive food legislation, applied at all stages of the food chain, and common to all EU member states. Nationally, food safety is addressed through cooperation and coordination between the various competent authorities at Central, Regional, and Local levels. In 2001, the Spanish Food Safety Agency was created, today known as the Spanish Agency for Food Safety and Nutrition, with the goal of promoting food safety as a key aspect of public health, and providing guarantees and objective information to consumers and other stakeholders in the sector.

Testing Laboratories: Conformity Assessment Bodies

Testing laboratories are conformity assessment bodies responsible for verifying, through analysis, that all regulations related to food quality and safety are met within the defined tolerance levels, while providing reliable and secure data that ensure confidence at the chemical, physical, organoleptic, or microbiological level regarding the sanitary suitability and quality of products.

Testing laboratories play different roles at all levels. From industry self-control laboratories to third-party laboratories that serve countless stakeholders (production quality control, specification checks for major distributors, large retailers, or specialized regulation controls such as Designations of Origin or product certifiers for different quality seals). Official control laboratories also play a fundamental role.

All of them have the obligation and responsibility to guarantee data that allow informed and safe decision-making, for example, whether to keep or withdraw a product from the market.

Technical competence and good practices are not only self-imposed requirements of the sector, but often, due to legal or contractual requirements (in the private sector), laboratories must demonstrate, through an impartial body, the validity of their data.

Accreditation According to ISO 17025

Accreditation under ISO 17025 is the highest standard that allows a laboratory to demonstrate its technical competence to perform specific tests. The application of this standard is often required, even in voluntary contexts, by clients in primary production and industry. Other food safety and management standards also specify tools for process measurement and control (including laboratories), among which is the participation in interlaboratory tests.

One of the most powerful, effective, and efficient tools that allows laboratories to demonstrate the quality of their data is successful participation in interlaboratory tests.

Interlaboratory Tests

An interlaboratory test involves the organization, execution, and evaluation of the results obtained from the analysis of identical samples by different laboratories, under pre-established conditions and with a defined objective.

Although the objectives of interlaboratory comparisons may vary, within the framework of laboratory quality control, the most common exercises are:

• Proficiency tests: aimed at comparing similar samples to assess the quality of the results issued by participating laboratories, using their usual working methodology and routine conditions (ISO 17043).
• Collaborative trials: aimed at comparing similar samples to obtain information on a specific method for a particular sample type, providing data on the accuracy and precision of the method in question (ISO 5725).

Analytical laboratories involved in food chain control, from raw materials to finished products, whether official or private, and accredited under ISO 17025, must participate in proficiency tests. In fact, section 7.7.2 of the standard states: “The laboratory shall monitor its performance by comparison with results from other laboratories, where available and appropriate. This monitoring shall be planned and reviewed and shall include participation in proficiency testing (ISO 17043) or other interlaboratory comparisons.”

Interlaboratory Tests: Mandatory Activity and Essential Tool

Therefore, interlaboratory tests have become not only a mandatory activity for monitoring the validity of results from ISO 17025 accredited laboratories, but also an essential tool for evaluating technical competence, especially when organized by competent, impartial, and accredited entities.

Beyond accreditation bodies, interlaboratory tests are increasingly demanded and valued by all types of recognition entities: food safety certification bodies, regulatory authorities, health authorities, large groups, and even major food retail chains, which require laboratories—whether authorized regional networks, in-house labs across different factories, or supplier labs—to undergo these exercises in order to ensure the reliability of their data.

Laboratories that achieve satisfactory results provide assurance, while those that do not must implement corrective actions to improve and guarantee their data, or risk exclusion or disqualification.

Providers of Interlaboratory Tests

For more than 10 years, GSC has been providing interlaboratory testing services as an accredited provider, helping many laboratories obtain or maintain their accreditations, authorizations, and certifications, according to the requirements of the requesting body. GSC provides real-sample testing and carries out independent and impartial evaluations.

The results obtained in recent years from GSC’s interlaboratory circuits related to food safety highlight the reliability of the data provided by participating laboratories from different perspectives, such as:

• Consistency with labeling data: High agreement is observed between the consensus average of participant results (after excluding outliers) and the values indicated by manufacturers on product labels. This reflects a high degree of reliability and assurance in the information provided to consumers.
  From the analysis of approximately 50 results on meat, vegetables, fish, pasta, ready meals, and other food products between 2013 and 2020, a strong correlation is observed between labeling data and interlaboratory results:

• Microbiological circuits: consistency with expected data and among laboratories. Another way to verify the adequacy of results from laboratories involved in food safety controls is through pathogenic microbiological parameters, which have a major impact on consumer safety.

Types of Samples in Interlaboratory Tests

It is essential that the analyzed sample be food-based, comparable in matrix and pathogens to those routinely received by laboratories, and designed to prevent manipulation or interference (e.g., lyophilized samples). This ensures that interlaboratory results provide a realistic view of what is happening in control laboratories.

From GSC’s experience as a PT provider, the data collected across various rounds show the adequacy of laboratory results compared to expected values based on inoculated pathogens, as well as consistency among labs. This makes them highly comparable, even when using different methods, avoiding contradictory or redundant controls.

For example, false negatives (cases where laboratories failed to detect or quantify pathogens that were present) were observed at very low rates. From the analysis of approximately 50 samples from different matrices contaminated with key foodborne pathogens (Salmonella spp and Listeria monocytogenes) at levels below 50 cfu/g, between 2013–2021, the percentage of correct results was highly satisfactory.

These data support the reliability of laboratory results throughout the food chain, building confidence in the work performed, and therefore in the decisions made by authorities and companies regarding product recalls, sanctions, or financial penalties, for example.

Over the years, increasing participation of laboratories in interlaboratory circuits reflects the responsibility and commitment of the entire industry—from laboratories themselves to large food companies requiring self-control labs to participate, as well as official entities promoting their own exercises to monitor official and private laboratories. It is no longer just an obligation but a recognition of the benefits that interlaboratory tests bring to trust across the food chain.

If you want more information about interlaboratory tests, you can contact the GSC team by calling +34 91 551 92 52, emailing gscsal@gscsal.com, or filling out the following form.