Overview
ISO 659:2009 - "Oilseeds - Determination of oil content (Reference method)" specifies a laboratory reference procedure for determining the hexane extract (oil content) of oilseeds used as industrial raw materials. The method has been validated on rapeseed, soybeans and sunflower seed but is applicable to other commercial oilseeds. A special subprocedure applies to sunflower seed, which requires an additional moisture determination after grinding.
Key topics and technical requirements
- Scope: Reference (gravimetric) determination of oil extracted with technical hexane or light petroleum (hexane extract = “oil content”).
- Solvent specification: Technical hexane / light petroleum - mainly C6 hydrocarbons; specified distillation ranges and low bromine value; residue on evaporation ≤ 2 mg/100 ml.
- Principle: Extract oil from a defined test portion using an appropriate extractor, evaporate solvent and weigh the extract.
- Apparatus: Analytical balance (±0.001 g), mechanical mills and microgrinders (producing <160 µm), extraction thimbles, suitable extractors (preferred straight-through types: Butt, Smalley, Bolton‑Williams) or validated Soxhlet use, ovens (103 ±2 °C and 130 ±2 °C), desiccator.
- Sample preparation: Follow ISO 664 for reduction of laboratory sample. Predrying is required so the test portion has moisture < 10% before extraction. Sunflower seed requires moisture measurement on whole seed per ISO 665, then grinding and re-measurement to correct for moisture loss during milling.
- Safety: Solvent removal and extraction steps must be done using appropriate ventilation (fume hood) and safe solvent‑handling practice.
- Quality metrics: The standard includes precision data (repeatability and reproducibility) from interlaboratory tests and prescribes how to express and calculate results.
Applications and who uses it
- Quality control laboratories in seed processing, edible oil and biodiesel industries
- Research labs and agricultural testing services measuring oil yield of rapeseed, soybeans, sunflower, groundnuts and other oilseeds
- Certification and inspection bodies requiring a reference (official) method for contract testing and trade
- Breeding programs and commodity traders assessing seed lots for commercial value
Related standards
- ISO 658 - Oilseeds: determination of content of impurities
- ISO 664 - Oilseeds: reduction of laboratory sample to test sample
- ISO 665 - Oilseeds: determination of moisture and volatile matter content
Keywords: ISO 659, oilseeds, oil content, hexane extract, reference method, sunflower seed, rapeseed, soybeans, extraction, moisture determination, seed testing, oilseed analysis.