Overview
ISO 12078:2006 (IDF 159:2006) is a reference method for determining the sterol composition of anhydrous milk fat using gas‑liquid chromatography (GLC). The standard defines a validated laboratory procedure - from sample preparation through chromatographic identification and quantification - to profile cholesterol and phytosterols in dairy fats. It is suitable for assessing milk fat purity and for detecting vegetable‑fat addition (validated on samples with ~28–32% vegetable fat).
Key topics and technical requirements
- Analytical principle: Addition of an internal standard (betulin), saponification (methanolic KOH), extraction of the unsaponifiable fraction, purification by thin‑layer chromatography (TLC), conversion to silyl derivatives and analysis by capillary GLC with a flame ionization detector (FID).
- Reagents and standards: High‑purity solvents (n‑hexane, di‑isopropyl ether, diethyl ether), betulin and cholesterol standard solutions, and phytosterol standards (campesterol, stigmasterol, β‑sitosterol) for qualitative evaluation.
- Apparatus: Typical laboratory glassware, TLC plates and developing tanks, rotary evaporator, nitrogen supply, micropipettes, and a gas‑liquid chromatograph with capillary column and FID. Carrier gases of high purity (hydrogen or helium) are specified.
- Procedure highlights: Saponification, unsaponifiable extraction, TLC purification to remove impurities, derivatization to silyl ethers, retention‑time identification against standards, and quantification by internal standard response factors.
- Quality and performance: The standard includes precision data from interlaboratory testing (repeatability and reproducibility) and prescribes reporting elements for test reports.
- Safety note: Use appropriate controls for volatile, flammable solvents and laboratory safety procedures.
Practical applications
- Dairy quality control: Verify the sterol profile of anhydrous milk fat for compositional specifications.
- Adulteration and authenticity testing: Detect and quantify vegetable fat blending in milk fat by profiling phytosterols.
- Regulatory compliance and labeling: Support claims about fat origin and content for food standards and labeling.
- Research and nutritional studies: Characterize sterol composition in dairy‑fat research and product development.
Who should use this standard
- Food and dairy analytical laboratories
- Quality assurance and regulatory testing teams
- Food chemists and R&D departments in dairy and ingredient manufacturers
- Laboratories conducting authenticity/adulteration screening
Related standards
- ISO 6799 - Sterol fraction analysis by gas‑liquid chromatography
- ISO 14156 | IDF 172 - Lipid extraction methods for milk and milk products
- ISO 3696 - Water for analytical use
Keywords: ISO 12078:2006, anhydrous milk fat, sterol composition, gas‑liquid chromatography, GLC reference method, dairy analysis, phytosterols, cholesterol.