Overview
EN ISO 11133:2014/A1:2018 (ISO 11133:2014/Amd 1:2018) is an amendment to the international standard on the preparation, production, storage and performance testing of culture media used in the microbiology of food, animal feed and water. Published by CEN in 2018, this amendment clarifies test criteria, updates definitions and inoculum levels, and adds procedural guidance for both solid and liquid media - including multipurpose diluents such as BPW (buffered peptone water).
Key topics and technical requirements
- Scope expansion: Confirms applicability to end-users and producers - commercial suppliers, non‑commercial suppliers and microbiology laboratories preparing media for internal use.
- Definitions: Revised definition of selectivity - non-target organisms that grow must not show the same visual characteristics as target organisms.
- Ingredient substitution: Allows hydrated/anhydrous ingredient substitution when molar mass is accounted for (e.g., Na2HPO4·12H2O).
- Inoculum levels and testing precision:
- Quantitative enumeration: target ~100 cfu per plate (practicable range 80–120 cfu; minimum 50 cfu).
- Qualitative and selectivity tests: minimum inocula revised (e.g., at least 10 cfu for selectivity/specificity in qualitative plate tests).
- Membrane filtration and liquid media testing: Guidance to assess discrepancies when filtration criteria are not met; specific acceptance thresholds for selectivity of liquid broths are defined (e.g., limits on non-target organism counts on non-selective agar).
- Multipurpose liquid media (e.g., BPW): Mandatory minimum qualitative pre‑enrichment testing with an appropriate pathogenic organism (for example, Salmonella) and expectations for suppliers to validate use as diluents for enumeration.
- Updates to annexes and test tables: Revisions to Tables E.1 and F.1 (selective & non-selective media), control strains, incubation conditions and references (including cross-references to ISO 6887-1, ISO 16649 series, ISO 15213).
Applications and users
This amendment is essential for:
- Food, feed and water microbiology laboratories performing isolation, enumeration and enrichment procedures.
- Manufacturers and distributors of culture media (ready-to-use, dehydrated, semi-finished).
- Quality assurance teams that validate media batches, perform performance testing and maintain compliance with ISO/CEN requirements.
- Regulatory and accreditation bodies assessing laboratory competence and media validation.
Related standards
Keywords: ISO 11133, culture media, performance testing, food microbiology, BPW, selectivity, specificity, enumeration, membrane filtration, media validation.