Overview
ISO 17410:2019 defines a horizontal method for the enumeration of psychrotrophic microorganisms in the food chain. The standard covers organisms able to form colonies on solid agar after aerobic incubation at 6.5 °C and applies to:
- products intended for human consumption and animal feed
- environmental samples from food and feed production and handling
- samples from the primary production stage
The document specifies surface‑plating procedures (plate count agar), incubation, counting rules and reporting. Annex B provides a rapid estimation method for raw and pasteurized milk (incubation at 21 °C for 25 h), with the caveat that not all psychrotrophs detected at 6.5 °C will grow at 21 °C.
Key topics and technical requirements
- Principle: Surface plating of a defined test portion or initial suspension, incubation at 6.5 °C ± 1 °C for 10 days, colony counting on plates with fewer than 150 colonies.
- Sample handling: Prepare test samples and decimal dilutions per ISO 6887 series; ensure representative sampling and proper transport/storage.
- Culture media and performance: Use Plate Count Agar (PCA); performance testing of media is required following ISO 11133 and Annex A.
- Procedure details:
- Dry plates before inoculation (per ISO 11133).
- Inoculate 0.1 mL (or 1.0 mL on larger plates to increase sensitivity) and evenly spread across agar surface.
- Incubate inverted plates at 6.5 °C for 10 days.
- Count colonies (include pinpoint colonies) and calculate results as number of psychrotrophic microorganisms per gram or per millilitre.
- Equipment: Incubator capable of 6.5 °C, sterile pipettes, spreaders, colony-counting device (optional), pH meter, refrigerator.
- Quality assurance: Control plates, contamination checks and adherence to ISO 7218 general microbiology requirements.
Practical applications
ISO 17410:2019 is used for:
- Quality control and shelf-life monitoring of refrigerated foods susceptible to psychrotrophic spoilage (dairy, meat, fish, ready-to-eat products).
- Dairy industry testing, including monitoring raw and pasteurized milk for psychrotrophic plate counts (rapid method available).
- Environmental monitoring in processing facilities to track refrigeration-related spoilage organisms.
- Regulatory testing and supplier verification where consistent, comparable enumeration of psychrotrophic microbes is required.
Who should use this standard
- Food and feed microbiology laboratories
- Dairy, meat, seafood and prepared-food manufacturers
- QA/QC managers, food safety auditors and regulatory laboratories
- Developers of diagnostic media and laboratory equipment
Related standards
- ISO 7218 - General requirements for microbiological examinations
- ISO 6887 (all parts) - Preparation of test samples and dilutions
- ISO 11133 - Culture media production and performance testing
- ISO 835, ISO 8655 - Laboratory pipettes and volumetric apparatus
Keywords: ISO 17410:2019, psychrotrophic microorganisms, enumeration, plate count, surface plating, 6.5 °C incubation, plate count agar, food microbiology, rapid milk method.
Open preview (PDF)Microbiology of the food chain — Horizontal method for the enumeration of psychrotrophic microorganisms