Bicarbonate of soda
A single alkaline compound that releases carbon dioxide when it meets an acid — and leaves a soapy residue when it does not.
Also called baking soda (US); sodium bicarbonate (TRADE)
Bicarbonate of soda is one compound, not a system. It releases carbon dioxide when it reacts with an acid in the presence of water, and it requires that acid to be supplied by something else in the formulation — buttermilk, yoghurt, natural cocoa, brown sugar, honey, lemon juice, or a sourdough culture.
Unreacted bicarbonate has a distinctly soapy, metallic taste and raises the batter’s pH, which darkens colour and accelerates browning. That is the signature of using too much, or of using it where no acid is available.
It is also why swapping natural cocoa for Dutch-processed cocoa in a recipe leavened with bicarbonate alone causes trouble: the alkalising treatment removed the acid the recipe was relying on.
What changes if it is left out
Baking powder can generally replace it, but not gram for gram — baking powder is substantially diluted by its acid and starch, so more is needed, and the batter’s own acid then goes unreacted, which changes flavour and colour.
BakeHQ deliberately does not publish a conversion ratio here. The correct amount depends on how much acid the formulation contains, which a single number cannot capture.
RecordedPaula Figoni, John Wiley & Sons
Related
Used in
Natural cocoa is acidic and can supply what bicarbonate of soda needs — which is exactly why swapping in Dutch-processed cocoa causes trouble.
The leavener, and the reason an acid is required.
The leavener, which needs that acid.
Leavening, and the alkalinity that darkens the biscuit.
What it does
pH modification
Raises pH where it goes unreacted, darkening colour and accelerating browning — and leaving the characteristic soapy taste.
Aeration
Releases carbon dioxide only when it meets an acid, which is the entire difference between it and baking powder.
Can be replaced by
Possible but not gram for gram: baking powder is diluted by its own acid and starch, so more is needed, and the recipe’s own acid is then left unreacted — which changes both flavour and colour. BakeHQ does not publish a single ratio because the right amount depends on how much acid the formulation contains.
Compared in
Baking powder vs bicarbonate of soda
The other side, and the one whose dependence on a recipe acid causes most of the confusion.
Commonly confused with
Routinely treated as interchangeable. One brings its own acid and the other does not, which is the whole difference and the source of most chemical-leavening faults.
History and culture
When baking stopped needing time
The alkali the whole development rests on.