A challenge test is process validation, not routine testing of every rPET batch. Its results support the scientific safety assessment; production must then maintain the validated operating conditions. The test does not replace a Commission authorisation decision.
Is a challenge test a quality test for every batch of rPET?
No. A challenge test is primarily a validation study used to assess the efficiency of a specific decontamination process. It helps demonstrate that the process removes representative contaminants sufficiently for the intended food contact application and identifies critical stages and parameters.
1. Why testing finished rPET alone is insufficient
Potential contaminants in waste PET can originate from previous use or misuse of packaging. Routine analysis of each batch cannot necessarily anticipate and identify all of them.
Process safety therefore relies substantially on demonstrated decontamination capability, alongside testing of the final material.
2. The challenge test deliberately challenges the process
Input material is contaminated with selected surrogate substances representing different chemical properties. It then passes through the key process stages, after which residual concentrations are measured.
The results are used to calculate removal efficiency for individual substances and assess the process’s ability to control the risk from unknown contaminants.
3. Surrogate contaminants are selected for a reason
Surrogates should represent different chemical behaviours and provide an adequate challenge to the process. The study must be designed so that its results can be related to the actual industrial process.
A simple laboratory test without a link to the technology’s configuration should therefore not be presented as equivalent to a properly designed challenge test.
4. The key result is decontamination efficiency
In its opinions, EFSA assesses how efficiently the process removes surrogate contaminants and whether the resulting migration is acceptable for the specified use scenario.
Many published PET assessments identify particular process stages as critical and specify the operating parameters that must be controlled during production.
5. Temperature, time, pressure and flow can be critical
Depending on the technology, critical parameters may include temperature, pressure or vacuum, residence time or gas flow. There is no single universal list for every installation.
Use the assessment of the specific process, the technology documentation and the relevant authorisation conditions to identify the applicable parameters.
6. Industrial operation must match validated conditions
A successful challenge test does not allow unrestricted subsequent operation. The recycler should demonstrate that the actual process operates under conditions delivering at least the required decontamination efficiency.
A deviation in a critical parameter is consequently a process control issue, even if the finished material looks normal.
7. The test supports EFSA assessment but is not a Commission decision
For mechanical PET recycling processes requiring individual authorisation, the test forms part of the scientific evaluation of process efficiency. EFSA issues its opinion; the European Commission decides on process authorisation.
“We have a challenge test, so we have authorisation” is therefore an incorrect conclusion. These are distinct stages.
8. A full challenge test is not performed for every batch
Routine production relies on process monitoring and material quality control. Where the installation operates under the conditions of the validated process, a full challenge test is not repeated for each batch.
Routine controls should instead demonstrate that the parameters and quality system keep the process within its validated operating conditions.
9. Technical changes can affect the relevance of an earlier test
Changes to residence time, reactor configuration, heating, vacuum, flow or another key element may change decontamination efficiency.
Change control should therefore determine whether a modification remains within approved conditions or requires further analysis, a new assessment or action involving the competent authorities.
10. Module A2 addresses control of the actual process
RecyClass Module A2 shifts attention from theoretical validation alone to whether the organisation has appropriate process documentation, controls parameters, maintains records, responds to deviations and preserves traceability.
Certification does not replace EFSA assessment or authorisation. It can verify specified requirements for systematic control of the plant’s process.
11. An example separates validation from monitoring
A challenge test may show that a process achieves the required efficiency at a particular temperature, residence time and vacuum. Routine control then checks whether each production campaign or batch ran under the required conditions.
Validation asks whether the process is capable; monitoring asks whether production actually operated within those conditions today.
Frequently asked questions
Does a challenge test establish the safety of the final bottle?
Not directly. Its primary role is to assess decontamination efficiency, which is then used in the safety assessment of a specified process and application.
Does every PET technology have the same critical parameters?
No. They depend on the configuration and mechanism of the particular process.
Is a positive EFSA opinion the same as authorisation?
No. EFSA performs the scientific assessment; the Commission decides on individual process authorisation.
Does an earlier challenge test always remain applicable after an installation change?
Do not assume this automatically. The change may require an assessment of its impact on the validated process.
Does RecyClass perform the challenge test?
A challenge test belongs to the technological and scientific assessment. RecyClass Module A2 assesses specified process and system requirements; it does not replace the test or regulatory procedures.