Overview
ISO 11746:2020 - Rice - Determination of biometric characteristics of kernels specifies a standardized, manual method for measuring the biometric characteristics (length, width, thickness) of husked or milled rice kernels. The method defines apparatus, sample preparation, measurement procedure, calculation of mean values and length/width ratio, precision limits, and required elements of the test report. It is intended to produce comparable, traceable kernel-size data for quality control, classification and research.
Key topics and technical requirements
- Scope: Applies to husked and milled rice kernels; sampling is not part of the method (ISO 24333 is recommended for sampling).
- Apparatus: sample divider or multiple-slot sampler, contrasting tray, tweezers, and a micrometer (or equivalent) readable to 0.01 mm that does not deform kernels.
- Sample preparation: Reduce aggregate sample (repeat dividing at least three times) to ~50 g, remove extraneous matter, immature, malformed or broken kernels.
- Measurement procedure:
- Randomly draw two sets of 100 kernels from the prepared test sample.
- Using tweezers to hold kernels in orientation specified in Annex A, measure length (l), width (b) and thickness (δ) with the micrometer; report to 0.01 mm.
- Verify random selection by checking percent difference between the two set means: |X1 − X2| / ((X1+X2)/2) × 100 ≤ 2; otherwise repeat selection.
- Calculations and reporting:
- Report arithmetic mean values for length, width, thickness (to 0.01 mm).
- Calculate length/width ratio l/b using the mean length and mean width.
- Precision:
- Repeatability limits (r): l = 0.125 mm, b = 0.049 mm, δ = 0.040 mm.
- Reproducibility limits (R): l = 0.337 mm, b = 0.163 mm, δ = 0.092 mm.
- Test report: Must include sample identification, sampling method (if known), reference to ISO 11746, operating details, results, repeatability check (if performed) and date.
Applications and who uses it
- Rice quality control laboratories and grain inspection services for classification, grading and lot acceptance.
- Rice breeders and agronomy researchers measuring kernel morphology for variety evaluation.
- Food processors and buyers who require standardized kernel-size data for milling performance, yield estimates and product specification.
- Certification bodies and interlaboratory studies requiring reproducible biometric measurements.
Related standards
- ISO 24333 - Sampling of cereals and cereal products (recommended sampling method).
- ISO 5725-1 / -2 - Accuracy (trueness and precision) of measurement methods (used for precision assessment).
- ISO 7301 - Rice specification (terminology and related provisions).
Keywords: ISO 11746:2020, rice biometric characteristics, kernel measurements, micrometer, length/width ratio, sampling, repeatability, reproducibility, rice quality control.