Microbial contamination is a major safety risk for consumers. The Challenge Test (Preservative Efficacy Test) verifies that your preservative system is robust enough to protect the product throughout its shelf life.
The ISO 11930 Standard
This is the gold standard for challenge testing in the EU. The test involves deliberately inoculating the product with specific strains of bacteria (e.g., E. coli, S. aureus), yeast (C. albicans), and mold (A. brasiliensis).
The Procedure
- Inoculation: A known concentration of microbes is added to the product.
- Incubation: The product is stored at a controlled temperature.
- Sampling: Samples are taken at intervals (e.g., 7, 14, and 28 days) to count the surviving microbes.
Criteria A vs. Criteria B
Criteria A represents a rapid reduction in microbial count, indicating a strong preservation system.Criteria B represents a slower reduction but no increase, which is acceptable but may require stricter packaging controls (e.g., airless pumps) or a shorter Period After Opening (PAO).
When is it NOT required?
ISO 29621 defines low-risk products that do not require challenge testing. These include:
- Products with high alcohol content (>20%).
- Products with extreme pH (<3 or >10).
- Anhydrous products (oils, waxes) with no water activity.
- Single-use sterile products.
Testing Services
We coordinate ISO 11930 testing with accredited Swiss laboratories. View our testing solutions.
PET is often conducted alongside Stability Testing to ensure comprehensive product safety.