Overview
ISO 21569:2005 - Foodstuffs: Methods of analysis for the detection of genetically modified organisms and derived products - Qualitative nucleic acid based methods - defines standardized procedures to qualitatively detect GMOs by analysing nucleic acids extracted from food matrices. The standard focuses on PCR-based amplification methods and provides guidelines, minimum requirements and performance criteria to ensure comparable, accurate and reproducible results across laboratories. Annexes A–D give concrete method examples (target-taxon-specific, screening, construct-specific and event-specific).
Key topics and technical requirements
- Scope and principle
- Qualitative detection gives a clear presence/absence answer for target DNA sequences relative to controls and method detection limits.
- Main emphasis on conventional and real-time PCR methods.
- Sample and nucleic acid quality
- Extracts must be free of PCR inhibitors; integrity and amplifiability influence detection limits, especially in processed foods.
- PCR design and reagents
- Recommended primer characteristics: 18–30 nucleotides, optimal annealing ~60 °C, balanced GC content; product size chosen to match DNA degradation (e.g., 60–150 bp for highly degraded material).
- Use of hot-start PCR is recommended to improve specificity.
- Note: dUTP use can interfere with subsequent restriction analyses.
- Performance and validation
- Performance criteria and method-specific values are provided in the annexes.
- Optimized PCR should detect ~100 copies of template DNA within 40 cycles under ideal conditions.
- Primer validation: (1) theoretical (sequence similarity search, e.g., BLAST), and (2) experimental specificity testing.
- Detection and confirmation
- PCR products may be detected by gel electrophoresis or real-time PCR; identity confirmation by restriction analysis, hybridization or DNA sequencing.
- Quality assurance
- Inclusion of appropriate positive/negative and inhibition controls, method reporting requirements and inter-laboratory comparability measures.
Practical applications and users
- Who uses it:
- Food and feed testing laboratories, regulatory agencies, contract analytical labs, environmental monitoring groups, seed and ingredient suppliers, and academic researchers.
- Practical uses:
- Regulatory compliance and labeling verification for GMO content.
- Routine surveillance and screening of raw materials and processed foods.
- Method development and validation for laboratories implementing qualitative GMO detection.
- Event- or construct-specific identification for traceability and enforcement.
Related standards
- ISO 21571 - Nucleic acid extraction (complementary procedures)
- ISO 21570 - Quantitative nucleic acid based methods
- ISO 21568 - Sampling for GMO analysis
- ISO 24276 - General requirements and definitions for nucleic-acid based GMO methods
Keywords: ISO 21569:2005, GMO detection, qualitative PCR, nucleic acid based methods, food analysis, primer validation, event-specific, construct-specific, screening methods.