Overview
EN ISO 1211:2010 (ISO 1211:2010) - "Milk - Determination of fat content - Gravimetric method (Reference method)" - specifies the reference gravimetric procedure for determining the fat content of milk of good physicochemical quality. The method is based on the classical Röse–Gottlieb extraction principle: an ammoniacal ethanolic test solution is extracted with a mixed solvent (diethyl ether and light petroleum), the solvents are removed, and the mass of extracted fat is determined gravimetrically.
This standard applies to raw cow, raw sheep, raw goat, reduced‑fat, skimmed, chemically preserved and processed liquid milk. It is not intended when greater accuracy is required for skimmed milk (e.g., to assess cream‑separator efficiency).
Key topics and technical requirements
- Principle: Extraction of fat using ammoniacal ethanol and a 1:1 mixture of diethyl ether and light petroleum; solvent removal by distillation/evaporation; gravimetric determination of extracted material.
- Reagents: Ammonia solution (~25% NH3), ethanol (≥94% v/v), diethyl ether (peroxide‑free), light petroleum (boiling range 30–60 °C or pentane equivalent), Congo red (optional indicator).
- Apparatus: Analytical balance (readability 0.1 mg), Mojonnier‑type fat extraction flasks/tubes (see ISO 3889), centrifuge capable of 500–600 min−1 (optional but recommended), distillation/evaporation equipment.
- Procedure elements: Sampling and test‑portion preparation, blank tests, fat‑collecting vessel preparation, solvent extraction, centrifugation/separation, solvent removal, calculation and expression of results.
- Quality/precision: The standard includes precision data (repeatability, reproducibility) and prescribes blank control and reagent purity checks to ensure reliable results.
- Safety: Use of flammable solvents (diethyl ether, light petroleum) and carcinogenic Congo red requires appropriate laboratory safety and ventilation.
Applications and users
Who uses EN ISO 1211:2010:
- Dairy laboratory analysts performing milk fat analysis for quality control and labeling.
- Food testing and regulatory laboratories that require a recognized reference method.
- Dairy industry R&D and production teams validating routine methods (e.g., Gerber, infrared) against a reference.
- Certification bodies and interlaboratory studies assessing method performance.
Practical uses:
- Accurate determination of fat content for product specification, nutrition labeling and process control.
- Reference benchmarking to validate faster routine methods.
- Comparative studies across milk types (cow, sheep, goat) and processed liquid milks.
Related standards
- ISO 3889 / IDF 219 - Specification of Mojonnier‑type fat extraction flasks.
- ISO 7208 - Special methods for skimmed milk when higher accuracy is required (not covered by ISO 1211).
- Annexes in ISO 1211:2010 provide notes on procedures, alternative fat‑extraction tubes and interlaboratory trial data.
Keywords: EN ISO 1211:2010, ISO 1211, milk fat determination, gravimetric method, Röse‑Gottlieb, reference method, milk analysis, Mojonnier, diethyl ether, light petroleum.