Overview
EN ISO 6887-1:2017 (ISO 6887-1:2017) - "Microbiology of the food chain - Preparation of test samples, initial suspension and decimal dilutions" - defines the general rules for aerobic preparation of the initial suspension and subsequent decimal dilutions used in microbiological examination of products intended for human or animal consumption. It is a horizontal (general) method: other parts of the ISO 6887 series cover specific product groups. The standard is relevant where matrix effects (e.g., inhibitors) may also influence molecular methods such as PCR.
Key topics and technical requirements
- Principle and scope: Provides a harmonized approach for preparing test portions, primary suspensions and dilution series for microbiological testing.
- Diluents: Guidance on selection and preparation of diluents (e.g., peptone salt solution, buffered peptone water, double‑strength buffered peptone water) and on sterilization, distribution and performance testing of diluents.
- Apparatus and sampling: General apparatus requirements and principles for representative sampling of foods and feeds.
- Sample preparation: Practical rules for different matrix types:
- frozen products (including handling of small vs large frozen pieces)
- hard, dry and low‑moisture products
- liquid and non‑viscous products
- acidic and high‑fat foods
- multi‑component and packaged products
- surface samples (swabs and other devices)
- Specific procedures: Instructions for choosing test portion size, making the initial suspension (primary dilution), timing of procedures, and pooling/compositing for qualitative tests.
- Further dilutions: Methods for preparing decimal dilution series and alternative dilution schemes.
- Informative annexes: Illustrations and protocols (e.g., pooling/compositing, sampling frozen blocks, reliability data, verification for pooling).
Applications and who uses it
- Food and feed microbiology laboratories performing enumeration and detection assays.
- Quality control (QC) and assurance teams in food production and processing plants.
- Regulatory and public‑health laboratories validating surveillance and compliance testing.
- Method developers and validation specialists, especially where matrix effects may impact culture-based or molecular (PCR) methods.
- Standardization bodies and auditors seeking harmonized, reproducible sample‑preparation protocols.
Benefits include improved comparability of results, reduced procedural variability, and clearer guidance when special matrices or inhibitory substances are present.
Related standards
- Other parts of the ISO 6887 series (product‑specific rules) complement this general document.
- When a specific International Standard prescribes sample preparation or diluents for a test method, that specific standard takes priority over the general rules in ISO 6887‑1:2017.
Keywords: ISO 6887-1:2017, microbiology of the food chain, sample preparation, initial suspension, decimal dilutions, food microbiology, diluents, PCR inhibition.