ISO 21415-3:2006

Overview

ISO 21415-3:2006 defines an oven-drying method to determine dry gluten from wet gluten obtained according to ISO 21415-1 or ISO 21415-2. The procedure yields the dry gluten content of a wheat, semolina or flour sample and can also be used to determine the moisture content of the wet gluten. The method is widely used for routine quality control, specification testing and laboratory reporting in cereal and milling laboratories.

Key Topics

• Principle: a ball of wet gluten is dried in an oven and weighed; the mass loss gives the water content and the residue is the dry gluten.
• Apparatus: typical laboratory equipment is required including a scalpel or knife, a 5 cm × 5 cm metal or glass plate, an oven capable of 130 °C ± 2 °C, a desiccator and a balance accurate to 0.01 g.
• Drying regime: the plate with wet gluten is dried at 130 °C for a total of 6 hours (initial 2 h, then incisions are made in the partially dried gluten, followed by a further 4 h), cooled in a desiccator and weighed.
• Calculations:
  • Dry gluten (%) = (mass_plate+dry_gluten − mass_empty_plate) / mass_original_sample × 100
  • Water content of wet gluten (%) = (mass_wet_gluten − mass_dry_gluten) / mass_wet_gluten × 100
• Precision: the method includes validated precision data. Repeatability limit r ≈ 0.6 g/100 g; reproducibility limits depend on the starting wet-gluten method (manual: R ≈ 3.1 g/100 g; mechanical: R ≈ 2.3 g/100 g).

Applications

• Routine laboratory determination of gluten content for quality assurance in flour, semolina and wheat processing.
• Determination of moisture in wet gluten to support process control and formulation.
• Regulatory and commercial testing where standardised, traceable gluten measurements are required.
• Useful in R&D, milling operations and ingredient specification where gluten strength and quantity impact end-product quality.

Related Standards

• ISO 21415-1: Determination of wet gluten by a manual method - source for the wet gluten sample.
• ISO 21415-2: Determination of wet gluten by mechanical means - alternative source for wet gluten.
• ISO 21415-4: Dry gluten determination by a rapid drying method - alternative drying procedure.
• ISO 712: Determination of moisture content of cereals and cereal products - used when results are expressed on a dry-matter basis.

Practical notes

• Report the method references (this part and the part used for wet gluten), sample identification, any deviations from the procedure and the arithmetic mean of duplicate determinations.
• Ensure oven temperature control, balance calibration and desiccator efficiency to meet the method precision.

This standard provides a robust, repeatable procedure for obtaining reliable dry-gluten and moisture data for quality control and laboratory use.