Overview
ISO 21528-1:2017 - "Microbiology of the food chain - Horizontal method for the detection and enumeration of Enterobacteriaceae - Part 1: Detection of Enterobacteriaceae" - specifies a validated, enrichment‑based laboratory method for the detection of Enterobacteriaceae in food, animal feed and related environmental samples. The standard is part of the ISO 21528 series and is intended for use when target organisms may require resuscitation by enrichment or when counts are expected to be below 100 per gram or millilitre.
Key topics and technical requirements
- Scope and applicability: Applies to products intended for human consumption, animal feeding stuffs, and environmental sampling in primary production, food production and food handling areas.
- Enrichment step: Buffered Peptone Water (BPW) is used for non‑selective pre‑enrichment, typically incubated at 37 °C (or optionally 30 °C for psychrotrophic considerations) for about 18 h.
- Isolation: Post‑enrichment cultures are plated on Violet Red Bile Glucose (VRBG) agar to detect typical presumptive Enterobacteriaceae colonies after incubation.
- Confirmation tests: Presumptive colonies are subcultured on non‑selective media and confirmed by glucose fermentation and oxidase reaction (negative oxidase indicates Enterobacteriaceae).
- Enumeration option: Enumeration can be performed by calculation of the Most Probable Number (MPN) after incubation in liquid medium (Annex A).
- Precision and limitations: The method can show significant variability (see Clause 11). It is intended for low‑count detection and when enrichment is required.
- Quality and equipment: References to media composition and performance testing (Annex B), and to general laboratory requirements (ISO 7218, ISO 11133). A skilled microbiologist and properly equipped laboratory are required; biosafety precautions are emphasized.
Practical applications and users
Who uses ISO 21528-1:2017:
- Food microbiology laboratories conducting routine hygiene and safety testing
- Quality assurance/quality control teams in food production and processing
- Veterinary and animal feed testing laboratories
- Regulatory agencies and auditors assessing environmental hygiene in food operations
Practical uses:
- Screening raw materials, finished products and surfaces for Enterobacteriaceae as hygiene indicators
- Investigating contamination routes in primary production and food handling environments
- Supporting compliance testing and comparative studies where enrichment‑based detection is required
Related standards
- ISO 7218 - General requirements for microbiological examinations
- ISO 6887 - Preparation of test samples and dilutions
- ISO 11133 - Preparation and performance testing of culture media
- ISO/TS 17728, ISO 13307, ISO 17604, ISO 18593 - Recommended sampling techniques for various matrices
- Other parts of the ISO 21528 series covering enumeration and complementary methods
This summary highlights the practical value of ISO 21528-1:2017 for food safety testing, Enterobacteriaceae detection, laboratory workflows, and regulatory compliance.
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