Overview
EN ISO 660:2020 - "Animal and vegetable fats and oils - Determination of acid value and acidity" (CEN adoption of ISO 660:2020) specifies standardized laboratory procedures to measure the acid value and acidity of fats and oils. The document defines three analytical methods (two titrimetric and one potentiometric) for refined and crude vegetable and animal fats and oils, including soapstock and technical fatty acids. Waxes and milk/milk‑derived fats are excluded. Results are reported preferably as acid value (mg KOH/g) or alternatively as acidity (percent free fatty acids, conventionally as oleic acid).
Key topics and technical requirements
- Methods specified
- Two titrimetric methods (cold solvent with indicator; hot ethanol with indicator).
- One potentiometric titration (cold solvent) - potentiometric method included as a reference.
- Scope and limitations
- Applicable to refined and crude animal/vegetable fats and oils and soapstock; does not apply to waxes or milk fats.
- Methods are non‑specific: they measure total acidity and cannot distinguish free fatty acids from mineral or other organic acids (acid value therefore includes any mineral acid present).
- Reagents and solvents
- Solvent mixture typically ethanol (≈96%) and diethyl ether (peroxide‑free) or approved alternatives (e.g., tert‑butyl methyl ether, toluene); neutralization before titration is required.
- Standard NaOH or KOH solutions (ethanolic or methanolic) with known concentration are used as titrants.
- Indicators and safety
- Colour indicators: thymolphthalein or Alkali Blue 6B preferred; phenolphthalein may only be used if no alternative is available (phenolphthalein has CMR classification).
- Apparatus, sampling and precision
- References to ISO laboratory glassware standards (ISO 385, ISO 1042), sample preparation (ISO 661) and water quality (ISO 3696).
- Precision data, repeatability and reproducibility are provided in the standard.
Applications and users
- Quality control laboratories in edible oil processing, rendering and refining industries
- Food analysts and regulatory testing bodies verifying compliance and labeling
- Traders and commodity inspectors assessing oil/fat quality for purchase/sale
- Research labs studying oil degradation, storage stability or refining efficiency
EN ISO 660:2020 provides a harmonized, reproducible approach for determining acidity and acid value - essential for product specification, shelf‑life assessment, process control and regulatory compliance in the fats and oils sector.
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