Overview
EN ISO 21571:2005 - "Foodstuffs - Methods of analysis for the detection of genetically modified organisms and derived products - Nucleic acid extraction" (CEN adoption of ISO 21571:2005) defines general requirements and validated methods for DNA extraction, purification and quantitation from food matrices. The standard focuses on producing nucleic acids suitable for downstream nucleic-acid-based analyses (e.g., PCR) and describes methods in Annex A (DNA extraction/purification) and Annex B (DNA quantitation). Though established for foods, it is applicable to related matrices such as grains and feed.
Key topics and technical requirements
- Objective: obtain DNA of sufficient quality (length, chemical purity, structural integrity) for qualitative and quantitative molecular testing.
- Extraction and purification: methods are provided in Annex A. Users may select alternative validated protocols adapted to the specific matrix.
- Quantitation methods (Annex B): physical (absorbance), fluorescent intercalating/binding agents, enzymatic (bioluminescence), or quantitative PCR (qPCR) - qPCR is recommended where DNA is degraded, low-abundance or in complex/composite matrices.
- Sample preparation: guidance on representative test portions, homogenization, and particle size - typical extraction test portions described range from 200 mg to 500 mg; practical upper test portion size guidance (technical reasons) is not to exceed 2 g, though larger portions may be needed for low-DNA samples. At least two test portions should be extracted.
- Laboratory requirements: contamination control, workspace organization and a forward flow principle to physically separate pre- and post-amplification areas to prevent cross-contamination (see ISO 24276 for more).
- Stability, interpretation and reporting: the standard covers DNA stability, result interpretation and required elements of the test report.
- Intellectual property note: some silica-based extraction procedures referenced may be subject to patent rights (EP 0389063 / US 5,234,809); licensing claims are noted in the standard.
Applications and users
Who uses EN ISO 21571:2005:
- Food testing laboratories performing GMO detection workflows (DNA extraction → PCR).
- Regulatory and official control bodies verifying GMO labeling and compliance.
- Feed and grain testing facilities where DNA-based methods are required.
- Laboratory method developers validating extraction protocols for specific matrices.
Practical uses:
- Establishing validated sample preparation and extraction workflows.
- Selecting DNA quantitation approaches appropriate for matrix and downstream qPCR assays.
- Implementing contamination control and reporting consistent with international best practice.
Related standards
- ISO 21569 - Qualitative nucleic acid-based methods (GMO detection)
- ISO 21570 - Quantitative nucleic acid-based methods (GMO detection)
- ISO 21568 - Sampling for GMO analysis
- ISO 24276 - General requirements and definitions for nucleic-acid-based GMO methods
Keywords: ISO 21571, EN ISO 21571:2005, DNA extraction, nucleic acid extraction, GMO detection, food analysis, PCR sample prep, DNA quantitation, CEN.
