ISO 5537:2023

Overview

ISO 5537:2023 (IDF 26:2023) is the international reference method for determining the moisture content of all types of dried milk and dried milk products. Published jointly by ISO and the International Dairy Federation (IDF), this standard specifies a controlled drying procedure - including apparatus, sample preparation and calculation - to measure non‑chemically bound water in milk powders and related products.

Key topics and technical requirements

• Scope: Applies to all dried milk and dried milk products; sampling guidance is referenced (ISO 707 | IDF 50).
• Principle: Loss of mass of a test portion after drying at a defined temperature with a controlled dry‑air flow.
• Critical parameters:
  • Drying temperature: 87 °C (±1 °C)
  • Drying time: 5 h
  • Dry air flow: 33 ml/min per column (±2 ml/min)
  • Test portion: ≈5.0 g (±0.3 g)
  • Use of columns, filters and controlled airflow in a ventilated oven to ensure reproducible drying
• Apparatus: Analytical balance (mg‑level readability), forced‑ventilation oven with a metal block and air channels, airflow meter, columns with filters, desiccator and dried silica gel.
• Preparation & procedure: Detailed steps for column conditioning, weighing, sample loading, oven drying and re‑weighing to determine moisture loss.
• Results & reporting: Calculation, expression of moisture as percent mass fraction, and inclusion of precision data (repeatability and reproducibility) are covered.
• Safety note: Users must address hazards associated with hot ovens, compressed air and laboratory handling.

Practical applications

ISO 5537:2023 is used in laboratories and quality systems where robust moisture determination is essential:

• Dairy manufacturers - production control and batch release for milk powder, infant formula, whey powder and other dried dairy products.
• Quality control & assurance - monitoring moisture for shelf‑life, caking risk, microbial stability and compliance with product specifications.
• Regulatory and contract testing labs - official or dispute resolution testing using a standardized reference method.
• Research and development - formulation and process optimization where accurate moisture measurement is required.

Using this reference method ensures consistent, comparable moisture results across suppliers, customers and regulatory bodies - critical for product quality, safety and trade.

Related standards

• ISO 707 | IDF 50 - recommended sampling of milk powders (sample representativity)
• ISO/IDF joint numbering: this publication is also identified as IDF 26:2023.

Keywords: ISO 5537:2023, dried milk, moisture content, reference method, milk powder testing, dairy quality control, IDF 26, drying oven, moisture determination.