Why does bread dough rise?
In yeast dough, fermentation produces carbon dioxide. Gas held within the dough expands it before baking; in sourdough, acid-producing bacteria also help shape the result.
- The scientific idea
- Fermentation
- Fields of science
- Biology, Chemistry
How it works
A rising loaf is evidence of work done before the oven is switched on. Baker's yeast ferments sugars and produces carbon dioxide and ethanol. Gas retained in the dough helps expand it.
Look closer
Sourdough adds another community to the story. Yeasts live alongside acid-producing bacteria, so the starter develops both gas and sourness. These communities are not identical in every jar. A study in which bakers used the same flour and recipe still found differing microbial communities and bread acidity. Fermentation is therefore more than a timer running on a bowl: it is metabolism carried out by organisms whose identities help shape the result.