Overview
ISO 6887-1:2017 - Microbiology of the food chain - Part 1: General rules for the preparation of the initial suspension and decimal dilutions - defines the horizontal, general rules for preparing test samples, the initial suspension (primary dilution) and subsequent decimal dilutions for aerobic microbiological examination of products intended for human or animal consumption. Published in 2017 (2nd edition), it applies to the general case; other parts of the ISO 6887 series give specific rules for particular product groups. The standard also notes aspects relevant to molecular methods (e.g., matrices that may inhibit PCR) and excludes cases where specific International Standards prescribe preparation steps.
Key topics and technical requirements
- Scope and definitions: clear terminology for laboratory sample, test portion, initial suspension, pooled and composite samples.
- Principle: how to obtain a representative, uniform initial suspension to support accurate enumeration or detection.
- Diluents: selection and preparation (e.g., peptone salt solution, buffered peptone water, double‑strength buffered peptone water), sterilization, distribution and performance testing.
- Apparatus and sampling: general equipment and laboratory sampling requirements.
- Matrix-specific sample preparation: general guidance for frozen products, hard/dry foods, low‑moisture or dehydrated products, liquids, acidic and high‑fat foods, multi‑component and packaged products, and surface samples (swabs).
- Test portion and dilution series: procedures for test portion size, creating the initial suspension (commonly 1:10), decimal dilution series and alternatives where justified.
- Pooling and compositing: procedures, verification and illustrative annexes for pooled and composite samples for qualitative tests.
- Documentation and safety: notes on hazardous materials, duration of procedures and when specific methods override general rules.
- Normative references: cross-references to ISO 7218 and ISO 11133.
Practical applications and users
ISO 6887-1:2017 is used by:
- Food and feed microbiology laboratories for standardized sample preparation, ensuring reproducible results.
- Quality control and HACCP teams in food manufacturers and feed producers.
- Third‑party testing laboratories and regulatory agencies performing routine microbial enumeration and detection.
- Method developers and laboratory auditors seeking a harmonized, general framework for preparing initial suspensions and dilution series.
Practical benefits include improved comparability between laboratories, reduced matrix-related artifacts (including PCR inhibition awareness), and guidance for pooling/compositing strategies.
Related standards
- ISO 6887 series (other parts cover specific product groups)
- ISO 7218 - General requirements for microbiological examinations
- ISO 11133 - Preparation, production and performance testing of culture media
Keywords: ISO 6887-1:2017, microbiology of the food chain, initial suspension, decimal dilutions, sample preparation, diluents, test portion, pooled samples.