Overview
ISO 7971-3:2019 specifies a routine method for determining the bulk density of cereals, referred to as mass per hectolitre (kg/hl). The standard covers measurement using manual or automatic mechanical, electric or electronic mass-per-hectolitre instruments and defines the measurement principle, apparatus requirements, procedural steps, expression of results and reporting. It is the second edition and complements instrument traceability requirements given in ISO 7971-2:2019.
Key topics and requirements
- Scope and principle: Mass per hectolitre is the ratio of cereal mass to the volume it occupies after controlled filling and flow conditions. Results depend on grain packing (void space) and grain density.
- Apparatus: Requirements for hand-operated and automatic measuring instruments, plus an analytical balance (readability 0.1 g or 0.01 g depending on container volume) and a spirit level. Annexes give example hand-operated designs (KERN, NILEMA LITRE).
- Instrument verification: All apparatus must be verified in accordance with ISO 7971-2 (traceability to a reference instrument).
- Procedure essentials:
- Remove large impurities and equilibrate sample temperature with the room.
- Perform duplicate determinations (preferably on two separate test portions).
- For hand-operated devices, ensure level base, avoid impacts when filling and follow manufacturer instructions.
- For automatic instruments, use correct cereal calibration, recommended sample volume and empty collector between samples.
- Expression of results: Use the arithmetic mean of two determinations (or mean of four if repeatability conditions are not met). Report to the nearest 0.1 kg/hl.
- Precision and uncertainty: The standard provides repeatability (example: r = 0.4 for a defined mass-per-hectolitre range), reproducibility guidance and critical difference values for within-lab (≈0.2 kg/hl) and between-lab (≈1.2 kg/hl) comparisons. Measurement uncertainty should be evaluated (e.g., using ISO 5725-2 data).
Applications
- Quality control and grading of cereals (wheat, barley, etc.)
- Commercial acceptance testing and contract compliance where hectolitre mass affects price or classification
- Calibration and verification of mass-per-hectolitre instruments
- Laboratory testing, research and storage monitoring to assess grain handling and packing properties
Who uses this standard
- Grain testing laboratories and QA/QC teams
- Grain traders and commodity inspectors
- Cereal processors and millers
- Instrument manufacturers and calibration laboratories
- Standards bodies and conformity assessment organizations
Related standards
- ISO 7971-2:2019 - method of traceability for measuring instruments (verification and reference instruments)
- Other parts of the ISO 7971 series (see ISO website for the complete list)
Keywords: ISO 7971-3, mass per hectolitre, bulk density of cereals, hectolitre mass, routine method, cereal testing, grain quality, instrument verification.
Open preview (PDF)Cereals — Determination of bulk density, called mass per hectolitre — Part 3: Routine method