Overview
EN ISO 5536:2013 (ISO 5536:2009) specifies the Karl Fischer (KF) method for determining the water content of milk fat products, specifically applicable to butteroil / anhydrous milk fat with water content up to 1.0 % (mass fraction). Adopted by CEN from ISO/IDF, this standard defines reagents, apparatus, procedure and calculation steps for accurate volumetric KF titration of milk fat matrices.
Key topics and requirements
- Scope: Analysis of milk fat products (butteroil/anhydrous butterfat) with ≤ 1.0 % water.
- Principle: Direct volumetric titration of the test sample with a commercially available, pyridine‑free two‑component KF reagent at approximately 40 °C; water content calculated from reagent volume used.
- Reagents:
- Two‑component pyridine‑free Karl Fischer reagent (or one‑component titration reagent with methanol as solvent).
- Titration component with water equivalent ≈ 2 mg/ml.
- 1‑Octanol and methanol (methanol water content ≤ 0.05 %).
- Water standard (w = 10 mg/g) for calibration of the titration component.
- Working medium: Mix equal volumes of solvent component and 1‑octanol (1+1) in the titration vessel (~30 ml recommended).
- Apparatus:
- Automatic volumetric KF titrator with 5 ml (preferred) or 10 ml burette, double‑jacketed titration vessel and water bath for controlled ~40 °C titrations.
- Analytical balance (readability 0.1 mg) and disposable syringes (5 ml or 10 ml).
- Key procedural controls:
- Determine KF apparatus drift daily (titration without sample) and express drift in mL/min or mg/min.
- Establish water equivalent of titration component via five replicate titrations using the water standard; report mean to three decimal places.
- Shut-off criterion: typically a 10 s stop delay or stop drift slightly above measured drift.
- Sample preparation: mix sample thoroughly at 35–40 °C to disperse water; typical test portion ≈ 5 g. Replicates recommended for accuracy.
Applications and users
- Who uses it: dairy quality control laboratories, butteroil producers, food testing laboratories, regulatory agencies and research institutes concerned with milk fat product quality and specification compliance.
- Why use it: precise, standardized measurement of low-level water content for product shelf-life assessment, quality control, specification verification, trade and regulatory compliance.
Related standards
- ISO 707 | IDF 50 (recommended sampling method for milk and milk products) is referenced for sampling practices.
- CEN adoption: EN ISO 5536:2013 is the CEN-endorsed version of ISO 5536:2009.
Keywords: EN ISO 5536:2013, ISO 5536:2009, Karl Fischer, water content, milk fat products, butteroil, KF titration, anhydrous milk fat, dairy laboratory.