Overview
EN ISO 7328:2008 (IDF 116:2008) is the reference gravimetric method for determining the fat content of most milk-based edible ices and ice mixes, including concentrated and dried mixes. Often referred to as the Röse‑Gottlieb principle, the method extracts fat from an ammoniacal ethanolic solution using a mixed solvent (diethyl ether and light petroleum or pentane) and determines fat by weighing the solvent‑extracted residue. The standard is published by CEN/ISO in collaboration with the International Dairy Federation (IDF).
Key Topics and Requirements
- Scope & limitations
- Applicable to most milk-based ice creams, edible ices, ice mixes, concentrated and dried mixes.
- Not suitable when high levels of emulsifiers, stabilizers/thickeners, egg yolk, fruits or certain combinations make the Röse‑Gottlieb approach inappropriate (use a Weibull‑Berntrop method - ISO 8262‑2 / IDF 124‑2).
- Principle
- Extraction of fat from an ammoniacal ethanol solution with diethyl ether and light petroleum (mixed solvent), followed by solvent removal and gravimetric determination of extracted fat.
- Reagents & materials
- Ammonia solution (~25% NH3), ethanol ≥94%, diethyl ether (peroxide‑free), light petroleum (30–60 °C) or pentane (recommended).
- Optional Congo red indicator to visualize phase separation.
- Apparatus & conditions
- Mojonnier‑type fat extraction flasks (ISO 3889 / IDF 219).
- Analytical balance with 1 mg capability (readability 0.1 mg).
- Centrifuge (500–600 min−1 producing ~80–90 g) - optional but recommended.
- Drying oven (102 °C ± 2 °C), water bath (65 °C ± 2 °C) and distillation/evaporation equipment (≤100 °C).
- Quality & precision
- The document includes precision data (repeatability and reproducibility) based on interlaboratory tests and blank test requirements for reagent purity.
- Safety
- Use of volatile, flammable solvents (diethyl ether, pentane) requires appropriate safety measures and compliant electrical equipment.
Applications and Users
- Who uses it: dairy laboratories, quality control teams in ice‑cream manufacturing, regulatory bodies, third‑party testing labs and R&D departments working on frozen dairy products.
- Practical uses:
- Regulatory compliance and labeling verification of fat content in ice cream and related products.
- Product development and formulation control (fat level verification in mixes and concentrates).
- Comparative testing and method validation in accredited testing laboratories.
Related Standards
- ISO 3889 / IDF 219 - Mojonnier‑type fat extraction flasks
- ISO 8262‑2 / IDF 124‑2 - Weibull‑Berntrop method (alternative for difficult matrices)
- ISO 835, ISO 1042, ISO 4788 - laboratory glassware specifications
Keywords: EN ISO 7328:2008, fat content, milk-based edible ices, gravimetric method, Röse‑Gottlieb, ice mixes, Mojonnier, pentane, diethyl ether, reference method.
