Overview
EN ISO 6887-1:2017/A1:2024 amends Part 1 of ISO 6887 (Microbiology of the food chain) to provide requirements and guidance on using a larger test portion size for qualitative methods. This CEN-endorsed amendment clarifies terminology and practical procedures for preparing test samples, initial suspensions and decimal dilutions when sample sizes exceed those described in an original method or validation document.
Key topics and technical requirements
- Definitions and terminology: introduces/updates terms such as composite sample, pooled sample, category, type, item, and larger test portion to ensure consistent sampling language.
- Composite vs pooled samples:
- Composite sample: mix of several like items where a standard-sized test portion is taken from the mixture (applicable to qualitative tests only).
- Pooled sample: combination of items where the entire mixture is the test portion (applicable to qualitative tests only).
- Larger single test portion: a test portion larger than that in the original method/validation; can be used for both qualitative and quantitative analyses.
- Procedural controls to reduce false negatives:
- Pre-warm primary pre-enrichment broth to intended incubation temperature before use.
- Check temperature profile of larger enrichment volumes to ensure time-to-target temperature and total incubation time meet individual standard requirements (e.g., ISO 6579-1:2017 guidance cited).
- Maintain validated dilution ratio (sample:diluent) and incubation conditions; increases to dilution may be allowed to overcome inhibitory food matrices (reference to ISO 6887-4:2017 examples).
- Handling oversized laboratory samples: samples larger than maximum may be split into multiple test portions (example in text: a 750 g sample split into two 375 g portions for Salmonella testing).
- Validation and verification: the amendment addresses requirements for validating or verifying the use of larger test portion sizes (see ISO 16140-4 references).
Practical applications
- Use in food microbiology laboratories, quality control, and regulatory testing when batch size, environmental sampling volume or legislation demands larger sample analysis.
- Helpful for Salmonella testing, environmental monitoring, and other qualitative microbiological assays where sensitivity and representativeness are critical.
- Guides decisions on compositing/pooling strategies to increase throughput while managing risk of false negatives.
Who should use this standard
- Accredited microbiology laboratories, food manufacturers’ QC units, method developers, conformity assessment bodies, and national regulators implementing or interpreting qualitative microbiological methods.
Related standards
Keywords: EN ISO 6887-1:2017/A1:2024, microbiology of the food chain, initial suspension, decimal dilutions, larger test portion, composite sample, pooled sample, qualitative methods, sample validation.