Overview
This document describes EN ISO 21571:2005/A1:2013 - Amendment 1 to ISO 21571:2005 - published by CEN/ISO. It updates the international method for nucleic acid extraction from foodstuffs for the detection of genetically modified organisms (GMOs) and derived products. The amendment clarifies references, strengthens requirements on sample handling and laboratory design, adds practical guidance (e.g., buffer example), and introduces a validated guanidine–chloroform DNA extraction protocol for soybean lecithin, including collaborative trial results and practical limits of detection.
Key topics and technical requirements
- Scope and references: Replaces and harmonizes normative references (notably ISO 24276:2006 - general requirements and definitions for GMO analysis) and removes older references (ISO 21568 where applicable).
- Laboratory design and contamination control: Refers laboratories to ISO 24276:2006 (laboratory design, section 5.3.2) to ensure appropriate segregation, workflow and contamination prevention for nucleic acid work.
- Sample preparation: Requires that laboratory samples be sufficiently homogeneous before reduction/grinding and before taking test portions; after treatments samples must be homogenized.
- DNA handling and assessment:
- Recommends assessment of extracted DNA quality using appropriate PCR controls (e.g., if analysis is PCR-based).
- Specifies that the total amount of DNA used in PCR and the total amount of target taxon DNA should be determined because non‑target DNA can affect PCR efficiency.
- Gives a practical buffer example: TE buffer (pH 8.0) is appropriate for re-suspending or diluting DNA.
- Validation and LOD calculation: Practical limit of detection (LODpractical) calculations follow ISO 24276 procedures; the amendment includes example calculations and collaborative validation data for lecithin samples (assumptions such as an LOD of 10 copies in example calculations are shown).
- New protocol: Adds A.5.2 - a guanidine–chloroform extraction protocol for DNA from soybean lecithin and cold-pressed oils, with validation status, intralaboratory and interlaboratory trial results and performance criteria.
Applications and users
- Who uses it: Food testing and enforcement laboratories, GMO testing providers, method developers, QA/QC teams in food industry and regulatory agencies.
- Practical uses:
- Standardizes DNA extraction practices ahead of PCR or real-time PCR GMO detection.
- Provides validated method options for challenging matrices (e.g., viscous lecithin, oils).
- Supports accurate LOD estimation and routine quality controls for compliance testing and enforcement.
- Guides lab design and sample handling to minimize contamination and improve reproducibility.
Related standards
- ISO 21571:2005 (original standard)
- ISO 24276:2006 - General requirements and definitions for GMO analysis (now the primary reference)
- ISO 21570 - Methods referenced for quantitation (e.g., soybean lectin real‑time PCR)
- (References to ISO 21568 were removed in this amendment)
Keywords: EN ISO 21571, ISO 21571:2005/A1:2013, nucleic acid extraction, GMO detection, food analysis, DNA extraction, soybean lecithin, real-time PCR, limit of detection, ISO 24276.
