Overview
ISO 17059:2019 specifies a rapid method for cold extraction of oil from selected oilseeds and for preparation of the fatty acid methyl esters (FAME) of triglyceride fatty acids for analysis by gas chromatography (GC). The method combines oil extraction and transesterification to reduce analysis time, laboratory workload and cost while providing representative FAME for GC profiling of common oilseeds.
Key scope points:
- Applicable to rape and mustard with low erucic acid (< 2%), sunflower, soya beans and linseed.
- The method uses an iso-octane extraction followed by potassium hydroxide–catalyzed transesterification to obtain methyl esters suitable for GC.
- A noted limitation: application to high-erucic rapeseed can overestimate erucic acid by ~1% mass fraction due to partial oil extraction; no correction factor is recommended.
Key Topics
- Principle: Cold extraction of crushed grain in iso-octane; filtration/drying if needed; transesterification of triglycerides with methanolic KOH to produce FAME for GC.
- Representative sampling and test portion: Sample reduction (ISO 664) and crushed sample portions are adapted to oil content to extract approximately 100 mg oil (examples in the standard: ~0.40 g for >30% oil seeds, ~0.80 g for 15–30% oil seeds).
- Procedure highlights:
- Add solvent (iso-octane), shake and allow to settle (extraction is rapid - typically a couple of minutes).
- Filter/dry extract through anhydrous sodium sulfate when needed; transfer extract for transesterification.
- Add methanolic potassium hydroxide (prepared/dried as specified) and neutralize with sodium hydrogen sulfate after reaction.
- Prepare the resulting iso-octane solution of FAME for injection depending on column and injection mode (packed column, capillary column, on-column options).
- Storage and handling: FAME solutions should be analyzed promptly; if stored, keep under inert gas in refrigeration. For longer storage protect against autoxidation (e.g., low-concentration BHT) as described in the standard.
Applications
- Rapid fatty-acid profiling of oilseed samples where full oil extraction is unnecessary or time/labor costs are a constraint.
- Routine laboratory screening for fatty acid composition prior to breeding, quality control or processing decisions.
- Use where GC analysis of FAME is the target analytical technique and the specified oilseeds are under study.
Practical benefits include reduced analysis time, simplified workflow, lower solvent and labor consumption, and generation of GC-ready FAME solutions.
Related Standards
- ISO 12966-4: Gas chromatography of fatty acid methyl esters - capillary GC determination (referenced for GC analysis procedures).
- ISO 664: Reduction of laboratory sample to test sample (sampling/sample preparation guidance).
- ISO 659: Determination of oil content (reference method used for comparison in validation studies).
For implementation, follow the standard's procedural steps, reagent and apparatus guidance, and the test-reporting requirements to ensure traceable, comparable results.