A wheat flour specification has to predict how the flour will behave in your process, not just describe it. Six numbers do most of that work: ash, protein, wet gluten, gluten index, falling number and a rheology value such as alveograph W. This guide shows what each predicts, which method stands behind it and how to write bands a mill can actually hold.
Key takeaways
- Ash defines the flour type; contract it as a band on dry matter with ISO 2171 named.
- Protein shows potential, gluten index shows strength; specify both, not protein alone.
- Falling number below the band means sprout damage and sticky crumb; above it, add malt or enzyme.
- Alveograph W and P/L separate bread, pizza and biscuit flours better than any grade name.
- Every number needs its method and its moisture basis, or two honest labs will disagree.
Start from the application
Bread, pizza, biscuits and wafers need opposite flours. A pan bread wants high protein with strong, elastic gluten. A rotary-moulded biscuit wants weak, extensible gluten and low water absorption. Write the application on the first line of the specification; every band below follows from it.
The six numbers
| Parameter | What it predicts | Reference method | How to write it |
|---|---|---|---|
| Ash | Refinement, colour, flour type | ISO 2171 | Band on dry matter |
| Protein | Volume potential, water uptake | ISO 16634-2 (Dumas) or Kjeldahl, N x 5.7 | Band, basis stated |
| Wet gluten | Gluten quantity | ISO 21415-2 | Band |
| Gluten index | Gluten strength | ISO 21415-2 | Minimum, sometimes maximum |
| Falling number | Enzyme activity, sprout damage | ISO 3093 | Minimum, and maximum for bread |
| Alveograph W, P/L | Dough strength and balance | ISO 27971 | Bands per application |
Ash. Flour ash is the mineral residue after incineration. Minerals sit in the bran, so ash tracks how much bran ended up in the flour. German type numbers (405, 550, 812, 1050) and French ones (T45, T55, T65, T80) are both read as ash on dry matter; Type 550 is roughly 550 mg of ash per 100 g of dry flour. These are national conventions; they bind only when the contract names them. A Ukrainian grade name does not map one-to-one to either system, so state the ash band itself.
Protein. Wheat protein is calculated from nitrogen with a factor of 5.7, while feed and many food labels use 6.25. The same flour can read 11.0 or 12.1 depending on the factor and on whether the result is on dry matter or at 14 per cent moisture. State both.
Gluten. Wet gluten measures how much gluten washes out of the dough; the gluten index measures how much of it resists a centrifuge, on a 0 to 100 scale. Two flours at the same protein can bake very differently if one has a weak index from heat-damaged or bug-damaged wheat.
Falling number. The falling number is the time in seconds a plunger takes to fall through a heated flour paste. Rain at harvest starts germination inside the kernel, alpha-amylase rises and the paste thins, so the number drops. As an indicative trade range, values below about 200 seconds give sticky crumb in bread, 250 seconds or more is a common bread specification, and very high values may need malt flour or enzyme to support fermentation.
Rheology. The alveograph blows a dough bubble and reports W (strength) and P/L (tenacity against extensibility). Indicatively, bread flours sit around W 180 to 250, long-fermentation pizza flours higher, and biscuit flours well below 150 with a low P/L. A farinograph (ISO 5530-1) adds water absorption and stability, which matters to plants that dose water by recipe.
Moisture, granulation and additions
Moisture is measured by the ISO 712 oven method; NIR readings are screening values. Granulation is a sieve fraction, and it changes water uptake and mixing time. Ascorbic acid and enzymes are common flour treatments; anything added must be declared and permitted for the destination, so the specification should say “no additions” or list them.
Contaminants are referenced, not restated
Mycotoxins, ergot and heavy metals in flour fall under Commission Regulation (EU) 2023/915. The contract should reference the instrument in force at shipment rather than copy figures that change with amendments. The mycotoxin guide explains sampling and testing.
Writing bands a mill can hold
A band that is narrower than the mill’s own process variation guarantees disputes. Ask the mill for three months of certificates for the flour you are buying, look at the spread of each parameter, and set the band around it. Then name the method, the moisture basis and the frequency of each test: ash, protein, wet gluten and falling number on every lot; rheology weekly or per agreed tonnage. For Ukrainian supply, add a clause on the August to September crop change; the wheat flour from Ukraine record lists the intake checks.
Reading a mill certificate against the specification
A certificate of analysis is only useful when every value on it can be traced to the line in your specification. Check four things on each certificate: the basis (as is, 14 percent moisture or dry matter), the method named for each value, the lot or silo the sample came from, and the date of analysis. A falling number measured on the wheat before milling is not the same as one measured on the flour, and an ash value on dry matter will read higher than the same flour reported as is.
When the first deliveries arrive, run your own intake tests on the parameters that drive your process and compare them with the certificate. A consistent offset between the two laboratories is normal and can be agreed; random scatter is a warning that the sampling or the method differs. Record the comparison for the first ten lots and use it to tighten or widen the bands at the next contract review.
For grain-side checks that feed into the flour result, see what falling number measures and what flour ash tells a buyer.
Checklist
- Application and target flour type stated as an ash band on dry matter
- Protein band with nitrogen factor and moisture basis
- Wet gluten band and gluten index minimum, ISO 21415-2
- Falling number minimum (and maximum for bread), ISO 3093
- Alveograph or farinograph bands where the process needs them
- Mycotoxin and residue position referenced by instrument
- Test frequency and the certificate content agreed per lot