Cluster article
Flour Granulation: Why Particle Size Matters More Than You Think
How to test and control flour granulation — sieve stacks, target distributions by application, what controls particle size, and why two flours at identical ash can behave completely differently.
Key takeaways
- Two flours at identical ash and protein behave differently if granulation differs — this explains most 'the flour changed' complaints.
- Granulation is controlled by roll gap, sifter screen aperture and detacher settings.
- Noodle flour needs uniform fine granulation; bread flour tolerates broader distribution.
Why it matters
Ash and protein tell you what is in the flour. Granulation tells you how it will behave.
Two flours at 0.55% ash and 12% protein can produce completely different bread if one has 30% of particles under 60 µm and the other has 15%. The fine fraction hydrates in seconds and is available to yeast immediately; the coarse fraction hydrates over minutes and colours the crust.
This is why “the flour changed” complaints are so often traceable to granulation drift rather than composition.
Testing
Equipment: sieve shaker + stack of 100, 150, 200, 250 mesh (150, 100, 75, 63 µm) sieves.
Method:
- Weigh 100 g of flour
- Stack sieves coarse to fine with a pan at the bottom
- Shake 10 minutes
- Weigh each fraction
- Report cumulative % passing each screen
Typical report:
| Screen | Passing |
|---|---|
| 100 mesh (150 µm) | 99.5% |
| 150 mesh (100 µm) | 92% |
| 200 mesh (75 µm) | 78% |
| 250 mesh (63 µm) | 61% |
Targets by application
| Application | Passing 200 mesh | Distribution |
|---|---|---|
| Bread | 85–95% | Broad acceptable |
| Noodle | 85–95% | Narrow, uniform |
| Biscuit | 80–90% | Moderate |
| Cake | 95%+ | Very fine |
| Atta | 70–85% | Coarse, deliberate |
| Semolina | <10% (different product) | 250–600 µm |
What controls it
| Control | Effect |
|---|---|
| Reduction roll gap | Smaller gap = finer flour |
| Reduction roll differential | Higher differential = more fines and more bran dust |
| Sifter screen aperture on flour passages | Directly sets cut point |
| Impact detacher | Breaks flakes, increasing passing fraction 5–12% |
| Roll condition | Dull rolls produce coarser, more variable flour |
The detacher effect
Smooth reduction rolls produce flat flakes. Those flakes behave as large particles in a sieve test but are actually thin and fragile.
An impact detacher breaks them apart, which:
- Increases the passing fraction by 5–12%
- Improves sifting efficiency
- Produces a more uniform distribution
Without a detacher, your granulation test may report a coarse flour that actually bakes fine — or a fine flour that bakes coarse. The measurement is misleading because flake dimension depends on orientation.
Drift diagnosis
| Symptom | Likely cause |
|---|---|
| Granulation coarser over weeks | Roll wear or fluting |
| Granulation suddenly coarser | Screen frame torn |
| Granulation suddenly finer | Roll gap closed or screen changed |
| Increased variability | Detacher pins worn, or feed rate unstable |
| Coarse fraction with high ash | Bran flakes — check break rolls and sifter |
Practical discipline
Test granulation:
- On every product change
- When a customer complains about behaviour
- Monthly as a trend check
- After any roll change or screen replacement
Do not test every shift. It consumes 20 minutes and rarely changes. Test when something is different.