ISO 5809:1982 PDF

Overview

ISO 5809:1982 specifies a standardized laboratory method for the determination of sulphated ash in starches and derived products. The procedure is based on controlled incineration of a test portion in the presence of sulphuric acid at 525 ± 25 °C. Results are reported as a percentage by mass, either as received or on a dry basis, and rounded to two decimal places. This method supports quality control, product specification and ingredient evaluation in starch processing and food industries.

Key topics and technical requirements

• Principle: Incineration of an accurately weighed test portion with sulphuric acid to convert volatile chlorides to non‑volatile sulphates and destroy organic matter.
• Temperature and equipment:
  • Electric furnace with air circulation controlled at 525 ± 25 °C.
  • Incineration dish (platinum or silica) capacity 100–200 ml, minimum useful surface 15 cm².
  • Analytical balance, desiccator, hot plate/gas burner, water bath (60–70 °C).
• Reagents:
  • Sulphuric acid solution: prepare by adding 100 ml concentrated H2SO4 to 300 ml water (handle carefully).
  • Hydrochloric acid cleaning solution: 100 ml concentrated HCl to 500 ml water.
• Procedure highlights:
  • Prepare and pre-calcinate the dish to constant mass (weigh to 0.0002 g).
  • Weigh representative test portion (typical sample ≈ 5 g; special dilution procedures provided for bulky samples).
  • Add 5 ml sulphuric acid solution to the sample, pre‑incinerate to carbonize, then incinerate in furnace until carbon residue disappears (typically ~2 h), cool, add drops of acid, re‑incinerate (~0.5 h) and weigh.
  • Perform two determinations and report the arithmetic mean if repeatability criteria are satisfied.
• Performance criteria:
  • Results expressed to two decimal places.
  • Repeatability and reproducibility limits are specified (e.g., reproducibility: 0.1 g/100 g for ash < 0.5%; 20% of mean for ash between 0.5–5%; 1% of mean for ash > 5%; repeatability limits also defined).

Applications and who uses it

• Quality control laboratories in starch production and starch‑derived product manufacturing.
• Food ingredient suppliers and formulators verifying mineral/ash content.
• Regulatory bodies and certification labs validating product compliance and label claims.
• Research and development groups studying composition, processing effects or formulations involving starches and syrups.
• Uses include specification compliance, contamination monitoring (e.g., mineral residues), product grading and formulation optimization.

Related standards

• ISO 1666 - Determination of moisture/loss on drying (relevant for dry‑basis reporting)
• ISO 1741, ISO 1742, ISO 1743 - Determination of dry matter for glucose/dextrose/glucose syrups

Keywords: ISO 5809, ISO 5809:1982, sulphated ash, starches and derived products, incineration method, ash content, analytical method, dry basis.