Overview - ISO 5550:2006 (Caseins and caseinates - moisture content, reference method)
ISO 5550:2006 (IDF 78:2006) specifies the reference method for determination of the moisture content of all types of caseins and caseinates. The standard defines the principle, apparatus, sample preparation, drying procedure, calculation and reporting rules for measuring moisture (expressed as a mass fraction in percent) in these dairy powders. It is intended for laboratories and organizations that require a validated, repeatable measurement procedure for quality control, specification compliance and regulatory testing.
Key topics and technical requirements
- Scope & principle: Moisture determined as mass loss after drying; test portion dried at 102 °C ± 2 °C and weighed until mass change stabilizes.
- Apparatus: Analytical balance (weighing to nearest 1 mg, readability 0.1 mg), ventilated drying oven, desiccator with desiccant, flat-bottomed non-corrodible dish (≥65 mm diameter), grinding device (no hammer‑mill), 500 µm test sieve.
- Sample preparation: Thorough mixing, sieving (500 µm) or grinding to pass sieve, immediate transfer to airtight container to prevent moisture change; recommended sampling reference ISO 707|IDF 50.
- Test portion & drying cycle: Typical test portions - ~5 g for caseins and ~2 g for caseinates. Dish and lid pre-dried (102 °C for ≥1 h), cooled in desiccator, weighed, then sample dried (3 h at 102 °C), cooled and weighed, then additional 1 h drying cycles until mass change ≤1 mg (take lowest mass). Total drying normally ≤6 h.
- Calculation & reporting: Moisture calculated from mass loss before/after drying; results reported to two decimal places.
- Precision (validated interlaboratory data):
- Repeatability limits (r): caseins 0.34%, caseinates 0.32%
- Reproducibility limits (R): caseins 0.53%, caseinates 0.41%
- Precision depends on casein grain size (see Annex B).
Applications - who uses ISO 5550:2006
- Dairy product manufacturers (casein/caseinate producers) for incoming/outgoing quality control and product specification.
- Food testing and analytical laboratories performing standardized moisture determinations.
- Regulatory and conformity assessment bodies requiring reference-method data for compliance.
- Research and R&D groups studying powder stability, shelf life, or processing effects on moisture.
Related standards
- ISO 707|IDF 50 - sampling of milk powders (recommended sampling method).
- ISO 5725 (interlaboratory precision methodology) - referenced for repeatability/reproducibility evaluation.
ISO 5550:2006 provides a robust, reproducible reference method for moisture analysis in caseins and caseinates - essential for accurate quality control, specification compliance and consistent reporting across laboratories. Keywords: ISO 5550:2006, caseins and caseinates, moisture content, reference method, drying oven, analytical balance, repeatability, reproducibility.
