Overview
ISO 6673:2025 - "Green coffee - Determination of loss in mass at 105 °C" defines a reference laboratory method for measuring the loss in mass at 105 °C of green (unroasted) coffee. The procedure is applicable to both decaffeinated and non‑decaffeinated green coffee (as defined in ISO 3509) and, by convention, can be used to determine water content. ISO 6673:2025 is intended as a reference method for calibrating routine moisture-determination methods.
Key topics and technical requirements
- Principle: Heat a test portion at 105 °C ± 1 °C for 16 h ± 0.5 h at atmospheric pressure; measure mass loss (principally water and volatile matter).
- Test portion: Approximately 10 g of green coffee spread in the dish.
- Apparatus:
- Oven with forced ventilation and calibrated temperature control.
- Dish with close-fitting lid (aluminium, glass or stainless steel; ≈90 mm diameter, 15–30 mm height).
- Analytical balance with 0.1 mg resolution.
- Desiccator with effective desiccant.
- Procedure highlights:
- Pre‑dry dish and lid at 105 °C, cool in desiccator, weigh.
- Weigh dish + sample (covered), dry with lid removed, cool, reweigh.
- Perform three determinations on the same test sample and report the arithmetic mean.
- Result expression:
- Loss in mass w (%) = (m0 − m1) / (m0 − m) × 100
- m = mass of dish + lid
- m0 = mass of dish + sample + lid before drying
- m1 = mass of dish + sample + lid after drying
- Uncertainty and precision:
- Uncertainty assessment follows ISO/IEC Guide 98-3 (GUM).
- Interlaboratory data (14 labs) show repeatability limits roughly 0.11–0.34% and reproducibility limits roughly 0.54–1.19%, depending on sample.
Applications and practical value
- Serves as a reference method for calibrating rapid or automated moisture analyzers used in coffee quality control.
- Used in quality assurance, incoming inspection, export/import testing, research, and method validation where an authoritative water-content measurement is required.
- Useful for establishing contract specifications and ensuring compliance with moisture-related storage and handling requirements (mold risk, weight-based trade).
Who should use ISO 6673:2025
- Coffee testing laboratories and QA/QC teams in green‑bean trading, roasting, and storage facilities.
- Regulatory and standards bodies, research institutions, and equipment manufacturers validating moisture measurement systems.
- Exporters, importers and commodity graders requiring a reproducible reference method.
Related standards
- ISO 3509 - Coffee vocabulary (definitions for decaffeinated/non‑decaffeinated).
- ISO 4072 - Recommended sampling for green coffee in bags.
- ISO/IEC Guide 98-3 (GUM) - Expression of measurement uncertainty.
- ISO 5725 series - Precision of measurement methods (interlaboratory studies).
