ISO 3433:2008

Overview

ISO 3433:2008 (IDF 222:2008) specifies the Van Gulik method for the determination of fat content in cheese expressed as a mass fraction (g per 100 g). The method is empirical and gives values equivalent to the reference method. It is applicable to all types of cheese, with a noted limitation: it may not give completely satisfactory results for cheeses with internal mould (blue‑veined cheeses).

Key topics and technical requirements

• Principle: Protein is dissolved in sulfuric acid, fat is liberated and separated in a Van Gulik butyrometer with the aid of iso‑amyl alcohol, and the fat column is read directly from the butyrometer scale.
• Reagents
  • Sulfuric acid: density at 20 °C (1.522 ± 0.005 g/ml) - corresponds to ~61.7–62.6% H2SO4; colourless or pale amber.
  • Iso‑amyl alcohol: minimum 99% primary alcohols (3‑methylbutan‑1‑ol and 2‑methylbutan‑1‑ol); density 0.808–0.818 g/ml at 20 °C; purity and distillation specifications and a suitability test are defined.
• Apparatus
  • Van Gulik butyrometers compliant with ISO 3432|IDF 221.
  • Centrifuge capable of producing (350 ± 50) g at the butyrometer stopper; rotational frequency tables provided for various radii.
  • Water bath maintained at (65 ± 2) °C, analytical balance (0.001 g), pipettes, grater for sample preparation.
• Procedure highlights
  • Remove rind and grind/mix sample; typical test portion is 3.000 g (weigh to 0.005 g).
  • Dissolve protein with sulfuric acid in butyrometer, add 1 ml iso‑amyl alcohol, heat, shake, centrifuge, and read the fat column.
  • Result expression: fat content (g per 100 g) = reading at top of fat column (B) minus reading at bottom (A).
• Limitations: dark or turbid fat columns or extraneous deposits can invalidate results; special note on blue‑veined cheeses.

Applications

• Routine dairy laboratory analysis and quality control for cheese fat labelling, upstream QC in cheese production, compliance testing for regulatory and trade purposes.
• Useful for product development, specification verification, and verifying fat content claims on packaging.
• Practical where a fast, empirical but standardized method is required that correlates with the reference method.

Related standards

• ISO 3432 | IDF 221:2007 - Butyrometer for Van Gulik method
• ISO 2446 - Milk - Determination of fat content (Gerber method)
• ISO 1735 | IDF 5 - Reference methods for fat determination (referenced)
• ISO 707 | IDF 50 - Recommended sampling methods for cheeses

Keywords: ISO 3433, Van Gulik method, cheese fat content, butyrometer, iso‑amyl alcohol, sulfuric acid, dairy laboratory, cheese quality control.