Rye flour vs wheat flour
Rye has the proteins and cannot build the network, so a rye dough is held together by something else entirely — which is why it is handled as though it were a different material.
The short answer
Rye contains gluten-forming proteins and does not form usable gluten, which is the fact everything else follows from — it is not gluten-free and it does not behave like wheat. What holds a rye dough together is pentosans: soluble fibres that absorb several times their weight in water and make the dough viscous rather than elastic. A high-rye dough is therefore sticky rather than stretchy, cannot be kneaded into strength, takes far more water, rises less and keeps for longer. It is also unusually rich in the enzyme that degrades starch, which is why traditional rye breads are soured: the acidity restrains the enzyme, and without it the crumb goes gummy.
Where they differ
| Dimension | First | Second |
|---|---|---|
| Gluten | Proteins present; no usable network forms. | Forms an elastic, extensible network when worked. |
| What holds the dough | Pentosans — soluble fibre making a viscous gel. | The gluten network. |
| Handling | Sticky, slack, not improved by kneading. | Elastic, and improved by working. |
| Water | Considerably more, because the pentosans hold so much of it. | Less, for the same handling feel. |
| Acidity | Usually soured, and the sourness is structural rather than a flavour choice. | Optional. |
| Keeping | Longer, because the held water is slow to leave. | Shorter. |
Differences that do not matter
These are real distinctions that are unlikely to change your decision. They are listed so you can stop thinking about them rather than left out so the comparison looks decisive.
- Suitable for coeliacs. No. Rye contains gluten and is not a gluten-free flour. No.
Why a rye loaf is soured and a wheat loaf need not be
The sourness of a traditional rye bread is not a regional preference. Rye carries a high level of amylase, the enzyme that breaks starch into sugars, and it stays active well into the bake — long enough to degrade the starch that should be setting the crumb. The result is the gummy, wet centre that a rye loaf made like a wheat loaf produces.
Acid slows that enzyme down. A sourdough rye is therefore acidified for a structural reason first and a flavour reason second, and the two are inseparable: the loaf that keeps its crumb is the loaf that tastes sour.
This is one of the clearest cases on the site where a traditional practice turns out to encode a mechanism nobody involved could have named.
Related
Compares
Why rye has the proteins and cannot build the network, and why that makes it a different material rather than a weaker flour.
Why rye has the proteins and cannot build the network, and why that makes it a different material rather than a weaker flour.