ISO 660:2020

ISO 660:2020 - Overview

ISO 660:2020 specifies standardized laboratory methods for the determination of acid value and acidity in animal and vegetable fats and oils. The standard defines three analytical procedures (two titrimetric and one potentiometric) and gives rules for sample preparation, reagents, apparatus, titration endpoints, calculation and reporting. Results are expressed preferably as acid value (mg KOH required to neutralize acids per g of fat) or alternatively as acidity / free fatty acid (FFA) content (percentage by mass).

Key topics and technical requirements

• Scope: Applicable to refined and crude vegetable or animal fats and oils, soap-stock fatty acids and technical fatty acids; excludes waxes and milk/milk‑derived fats (see ISO 1740 for milk).
• Methods:
  • Cold solvent titration using an indicator (reference method).
  • Cold solvent potentiometric titration using an electrode (reference method).
  • Hot ethanol titration using an indicator (alternative method; short-chain volatile acids can be lost).
• Reagents & solvents: neutralized solvent mixtures (ethanol + diethyl ether or alternatives), ethanolic/methanolic NaOH or KOH standard solutions (examples in the standard: 0.1 mol/L, 0.5 mol/L), and indicators (thymolphthalein, alkali blue or phenolphthalein - with CMR safety notes).
• Apparatus: burettes, analytical balance, combined pH electrode/automatic titrator for potentiometric method, volumetric flasks, etc.
• Non‑specificity: Methods measure total acidity and do not distinguish free fatty acids from mineral or other organic acids - acid value includes any mineral acids present.
• Calculation & reporting: Acid value expressed as mg KOH/g; acidity as % mass (commonly calculated on oleic acid basis by convention). Precision data (repeatability and reproducibility) and required reporting details are included.

Practical applications

• Quality control of edible oils, fats and technical fatty-acid products.
• Monitoring refining, storage and handling processes (hydrolysis/oxidation indicators).
• Specification testing for commercial trade and conformity assessment.
• Troubleshooting in processing plants (identifying increased free fatty acid levels).
• Reference method for interlaboratory comparisons and accredited testing labs.

Who should use ISO 660:2020

• Oilseed processors, edible‑oil refiners and animal‑fat producers
• Food and chemical testing laboratories and QA/QC teams
• Regulatory bodies and standards laboratories
• Research labs studying lipid degradation, shelf life or processing effects

Related standards

• ISO 661 - Preparation of test sample (fats and oils)
• ISO 385, ISO 1042 - Laboratory glassware specifications
• ISO 3696 - Water for analytical laboratory use
• ISO 5555 - Recommended sampling methods
• ISO 1740 - Determination of acidity in milk fats (for milk products)

Keywords: ISO 660:2020, acid value, acidity, animal and vegetable fats and oils, titrimetric, potentiometric, free fatty acids, analytical method, cold solvent method, hot ethanol method.