Overview
ISO 21415-1:2006 - "Wheat and wheat flour - Gluten content - Part 1: Determination of wet gluten by a manual method" - defines a validated manual washing‑out procedure to determine the wet gluten content of wheat flour, with applicability to semolina and ground wheat when particle size requirements are met. The method isolates hydrated gluten (gliadin + glutenin) from a dough prepared with a 20 g/L sodium chloride solution, followed by hand washing, removal of excess moisture using a gluten press, and weighing of the wet gluten.
Key topics and requirements
- Scope: Applies directly to wheat flour (Triticum aestivum and Triticum durum) and, with pre‑grinding to the specified particle size, to semolina and whole wheat.
- Sample prep & moisture: Homogenize and determine moisture (per ISO 712) before testing; grinding procedures for whole wheat are specified in Annex B.
- Reagents: 20 g/L sodium chloride solution for dough/washing and Lugol’s iodine/potassium iodide for starch detection.
- Apparatus: Porcelain mortar or enamelled vessel, 25 ml burette, balance (0.01 g), wooden frame with 308 µm gauze, gluten press, small‑scale mill, gloves, watch‑glass.
- Procedure highlights:
- Test portion ≈24 g; add 12 ml NaCl solution dropwise to form dough.
- Rest dough under humid cover for 30 minutes to allow gluten development.
- Wash out by hand over gauze with NaCl solution (typical washing ≈8 minutes; flow ~750 ml per 8 min).
- Continue washing until absence of starch (iodine test).
- Remove excess wash by repeated pressing in a gluten press and weigh wet gluten.
- Results & calculation: Wet gluten content expressed as percent of the test sample using the masses of test portion, dough portion and wet gluten (standard gives the calculation and instructs to report results to one decimal place).
- Precision: Repeatability and reproducibility figures are provided (example: for wheat flour r = 1.5 g/100 g; R = 7.7 g/100 g).
Applications and users
- Who uses it: Grain and flour testing laboratories, milling and semolina producers, cereal quality control teams, ingredient suppliers, food manufacturers, research institutions, and regulators.
- Why it’s used: To quantify wet gluten for quality grading, process control (baking performance, dough handling), specification compliance, and product development where gluten functionality matters.
- Practical value: The manual method is simple, low‑cost (no specialised mechanical washer needed), and is especially relevant where full gluten development must be ensured - the method can yield higher wet gluten values than mechanical washing for high‑gluten wheats.
Related standards
- ISO 21415-2: Mechanical determination of wet gluten.
- ISO 21415-3 / -4: Methods for determination of dry gluten from wet gluten.
- ISO 712: Moisture determination for cereals and cereal products.
- Refer to the full ISO 21415-1:2006 text for complete procedural details, annexes (gluten press design, grinding), and reporting requirements.
Open preview (PDF)Wheat and wheat flour — Gluten content — Part 1: Determination of wet gluten by a manual method