Overview
ISO 24557:2009 - "Pulses - Determination of moisture content - Air-oven method" is an ISO reference method for measuring moisture content in pulses. It applies to chickpeas, lentils, peas and all classes of beans (except soybeans) and defines a routine laboratory procedure based on loss of mass on drying (air‑oven). The method is suitable for quality control, trading, research and regulatory testing where reliable moisture determination of pulse commodities is required.
Key topics and technical requirements
- Principle: moisture content is determined as the percentage loss of mass when a representative, preconditioned and ground test portion is dried under specified oven conditions.
- Scope: excludes soybeans; intended for chickpeas, lentils, peas and beans.
- Preconditioning: reduce sample moisture to about 9–11% mass fraction (preferred: 130 °C for 15 min then cool 2 h; optional: air‑dry 48 h).
- Grinding: use a laboratory mill that does not overheat or overly expose the sample; required particle-size distribution (e.g., >20% <0.5 mm, 70% <1.0 mm, 100% <1.7 mm). High-speed grinders (>3 600 r/min) are discouraged.
- Drying: oven (gravity or mechanical convection) maintained at 130 °C ± 1 °C; test portions (2–3 g) are dried for 120 minutes after temperature recovery.
- Apparatus: laboratory mill, convection oven, heavy‑gauge aluminium moisture dishes with lids, airtight desiccator, analytical balance (±0.001 g).
- Calculation & reporting: moisture expressed as % mass fraction; use ISO’s equation based on masses before/after preconditioning and before/after oven drying. Report mean of two valid determinations rounded to one decimal place.
- Precision: interlaboratory data give a repeatability limit r ≈ 0.3% and reproducibility limit R ≈ 0.5% (statistical annex).
Applications and who uses it
- Food and cereal laboratories performing moisture analysis for quality control and inventory management.
- Grain traders and commodity graders verifying moisture for sale, storage and transport decisions.
- Research institutions studying pulse composition, storage stability and processing behavior.
- Regulatory bodies and inspection laboratories requiring an approved reference method for official testing.
Related standards
- ISO 24333 - sampling of cereals and cereal products (recommended sampling practice)
- ISO 5725‑1 / ISO 5725‑2 - accuracy (trueness and precision) of measurement methods
- AACC method 44‑17 - the air‑oven pulse moisture method on which ISO 24557 is based
Keywords: ISO 24557:2009, moisture content, pulses, air‑oven method, chickpeas, lentils, peas, beans, laboratory mill, oven 130 °C, repeatability, reproducibility.