Demerara sugar vs brown sugar
One keeps molasses it never lost and the other has molasses added back, and the difference shows up as moisture rather than as colour.
The short answer
Both are brown and they get there by opposite routes. Demerara is a partly refined cane sugar that never had all its molasses removed, and it keeps large, hard, dry crystals. Soft brown sugar is fully refined white sugar with molasses stirred back in, so it is fine, damp and clumping. The consequence is textural rather than chromatic: soft brown sugar dissolves readily and brings measurable moisture and acidity into a bake, and demerara largely does not dissolve and stays as crunch. Swapping demerara into a cookie recipe written for soft brown gives a drier, paler, crunchier result, and swapping the other way loses the crackly top the demerara was there for.
Where they differ
| Dimension | First | Second |
|---|---|---|
| How it got brown | Never fully refined — molasses it never lost. | Refined white sugar with molasses added back. |
| Crystal | Large, hard, dry. | Fine, damp, clumping. |
| Moisture contributed | Very little. | Real, and part of why brown-sugar bakes are softer and keep better. |
| Dissolving | Slow and often incomplete — it survives as crunch. | Readily. |
| Acidity | Slight. | Enough to react with bicarbonate of soda, which some recipes rely on. |
| Best use | A crunchy topping, a crackled crust, coffee. | Creamed into a batter, or anywhere chew and keeping matter. |
Why the swap fails in one direction more than the other
Going from soft brown to demerara removes both the moisture and the fine crystal, and the second is the one people forget. Creaming depends on crystals of roughly the right size cutting air into the fat; demerara's are too large and too hard, and a cookie creamed with it aerates less as well as being drier.
Going from demerara to soft brown is more forgiving in the mixture and disappointing on top, because the whole point of demerara scattered over a crumble or a loaf is that it does not dissolve. Soft brown sugar in that position melts into the surface and disappears.
Muscovado is a third thing again — very dark, very damp, and strongly flavoured — and BakeHQ compares it with demerara separately.
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Compares
Two brown sugars that got there by opposite routes, and why the difference shows up as moisture rather than colour.
Two brown sugars that got there by opposite routes, and why the difference shows up as moisture rather than colour.