ISO 6647-2:2020

Overview

ISO 6647-2:2020 specifies two simplified, spectrophotometric routine methods for determining the amylose mass fraction of milled, non‑parboiled rice. The standard covers routine laboratory procedures that omit the defatting step used in the reference method (ISO 6647‑1) and instead use calibration from rice standards whose amylose content has been established by the reference method. Two dispersion alternatives are defined: Method A (hot dispersion) and Method B (cold dispersion). Both methods are applicable to rice samples with an amylose mass fraction greater than 5%.

Key topics and technical requirements

• Scope and applicability: Routine determination of amylose in milled, non‑parboiled rice (>5% amylose).
• Principle: Grind rice to a fine flour, disperse starch in NaOH, react an aliquot with iodine and measure absorbance (typical wavelength 720 nm; 620 nm or 680 nm also acceptable).
• Dispersion procedures:
  • Method A: hot dispersion - 1 mol/L NaOH and 10 min heating in a boiling water bath.
  • Method B: cold dispersion - 2 mol/L NaOH and 10 min high‑speed magnetic stirring.
• Sample preparation: Grind to pass 150–180 µm sieve; typical test portion 100 mg; add ethanol to wet sample before alkali dispersion.
• Calibration: Use at least four rice standards (or a certified reference material) whose amylose mass fraction was determined independently by ISO 6647‑1; plot absorbance versus amylose mass fraction to create the calibration graph.
• Reagents and apparatus: Standard analytical reagents (ethanol, NaOH, acetic acid, iodine solution), spectrophotometer (1 cm cells), grinder, sieve, volumetric glassware. Blank solutions and dual determinations are required.
• Results and precision: Report amylose on a dry basis, as the mean of two determinations. The standard includes precision data and interlaboratory results (see Clause 10 and Annex A).

Applications and users

ISO 6647-2:2020 is designed for routine use where timely, reproducible amylose results are needed:

• Quality control laboratories in rice milling and processing plants
• Cereal and food analysis laboratories performing routine screening
• Rice breeding and research facilities monitoring amylose phenotype
• Regulatory and trade laboratories requiring standardized methods The method is suited where the defatting step is impractical or time‑consuming and where calibration against rice‑based standards improves comparability with the ISO 6647 reference method.

Related standards

• ISO 6647‑1:2020 - Reference spectrophotometric method (with defatting)
• ISO 712 - Moisture determination for cereals
• ISO 7301 - Rice specification
• ISO 8466‑1 - Calibration and statistical evaluation of analytical methods
• ISO 24333 - Recommended sampling for rice

Keywords: ISO 6647-2:2020, amylose content, rice amylose determination, spectrophotometric routine method, milled rice, calibration from rice standards, hot dispersion, cold dispersion.