Overview
ISO 1572:1980 specifies a standardized laboratory method for preparing a ground sample of tea and determining its dry matter content. The procedure ensures analytical results can be reported on a dry basis by grinding the sample to a defined fineness and drying a test portion in an oven at 103 ± 2 °C to constant mass.
Key topics and technical requirements
- Scope: Preparation of ground tea sample and determination of dry matter for analytical determinations requiring dry-basis results.
- Grinding: Use a grinding mill made of non‑moisture‑absorbing material, easy to clean and with minimal dead space. Ground material must pass a 500 µm sieve (see ISO 565).
- Pre-drying: If moisture is too high for satisfactory grinding, pre-dry a portion of the sample, cool, then grind.
- Sample handling:
- Transfer grindings into a clean, dry, airtight sample container (preferably glass) nearly filled by the ground sample.
- Use a squat weighing bottle with airtight lid for drying tests.
- Drying conditions:
- Heat weighing bottle and lid for 1 h at 103 ± 2 °C before use; cool in a desiccator and tare.
- Weigh a test portion (about 5 g) to 0.001 g accuracy.
- Dry with lid removed at 103 ± 2 °C, initially for 6 h, then repeat heating (typically 1 h) and cooling cycles until weight change between successive weighings is ≤ 0.005 g (constant mass).
- Calculation and repeatability:
- Dry matter (%) = (mass of dried test portion / initial mass of test portion) × 100.
- Perform two determinations and report the mean, provided repeatability criteria are met.
- Repeatability requirement: difference between two determinations by the same analyst should not exceed 0.3 g dry matter per 100 g sample.
Applications and users
ISO 1572:1980 is primarily used by:
- Tea testing and quality-control laboratories
- Food and beverage analytical laboratories reporting results on a dry basis
- Manufacturers and processors verifying moisture/dry matter for product specification, shelf‑life and blending
- Regulatory bodies and certification agencies performing standardized moisture determinations
- Research groups studying tea composition or processing effects
Practical benefits include reproducible dry-matter values, improved comparability of moisture-related analyses (e.g., concentrations expressed on dry basis), and standardized sample preparation for downstream tests.
Related standards
- ISO 1839 - Tea - Sampling (for representative sample collection)
- ISO 565 - Test sieves - nominal aperture sizes (for sieve specification)
- ISO/TC 34 (Agricultural food products) is the responsible technical committee.
Keywords: ISO 1572:1980, tea, dry matter content, ground sample, oven 103±2°C, grinding mill, sample preparation, ISO 1839, ISO 565.