Overview - ISO 6647-1:2020 (Rice - Determination of amylose content)
ISO 6647-1:2020 specifies a reference spectrophotometric method for determining the amylose mass fraction of milled, non‑parboiled rice (applicable when amylose > 5%). The method uses a defatting procedure with methanol and a calibration curve based on potato amylose and waxy (glutinous) rice amylopectin. Results obtained with this standard can be compared with PDO/PGI legislative limits and, where validated, applied to husked rice, maize, millet and other cereals.
Key topics and requirements
- Principle: finely ground, defatted rice flour is dispersed in NaOH; an aliquot is reacted with iodine and absorbance is measured at 720 nm. Amylose content is read from a calibration graph that corrects for amylopectin interference.
- Defatting & sample prep: flour must be milled to pass a 150–180 µm sieve and defatted by refluxing with methanol; samples and calibration stocks are conditioned to stable moisture before analysis.
- Calibration: uses stock suspensions (1 g/L) of defatted potato amylose and waxy rice amylopectin mixed in defined ratios to prepare the calibration series. Potato amylose purity and amylopectin iodine‑binding capacity are checked (see Annex A).
- Reagents & apparatus: analytical‑grade methanol/ethanol, NaOH solutions, iodine reagent, laboratory blender, cyclone mill or equivalent, reflux extraction apparatus, and a spectrophotometer with 1 cm cells capable of 720 nm measurements.
- Procedure & quality: detailed steps for test portion preparation, blank preparation, colour development, spectrophotometric measurement, expression of results, and reporting are defined. The standard includes precision data (interlaboratory test, repeatability, reproducibility) and informative annexes (e.g., interlaboratory results and an example flow injection analyser).
Applications and users
ISO 6647-1:2020 is intended for:
- Food testing laboratories performing routine or reference amylose determinations.
- Rice processors and breeders monitoring varietal amylose levels for quality and breeding decisions.
- Regulatory authorities and certification bodies assessing compliance with PDO/PGI specifications and labeling rules.
- Cereal researchers and product developers studying starch functionality (cooking, texture, nutritional properties).
Practical benefits include a standardized, comparable method for amylose quantification, minimized lipid interference via methanol defatting, and calibration that accounts for amylopectin effects on iodine binding.
Related standards
- ISO 712 (moisture determination) - used for moisture corrections when stocks and samples are not conditioned identically.
- ISO 8466‑1 and ISO 15914 - referenced for calibration evaluation and starch analysis methods.