Sponge cake
A cake raised principally by air whisked into egg, which makes it the category where technique matters more than formulation.
Also called victoria sponge (UK), genoise (INTERNATIONAL), sponge (UK), foam cake (US)
A sponge is a cake whose lift comes substantially from air beaten into eggs, rather than from a chemical leavener alone.
That single fact explains the method. The eggs and sugar are whisked to a foam that holds a visible ribbon; the flour is folded rather than stirred, because stirring collapses the foam that is doing the work; and the batter goes into the oven promptly, because the foam is not stable indefinitely.
A true genoise uses no chemical leavener at all and relies entirely on the whisked foam and on steam. The everyday creamed sponge — the Victoria — sits between the two, using creamed butter and sugar to trap air and baking powder to insure it.
Structure is set by egg protein coagulating and starch gelatinising, in a batter deliberately low in developed gluten. This is why sponge recipes specify a soft, low-protein flour and why overmixing produces something closer to bread.
What it should be like
- Structure
- Fine, even, open crumb
- Volume
- High rise relative to the batter weight
- Tenderness
- Tender, with little chew
Why a sponge sinks in the middle
A sponge that rises and then sinks has set its edges before its centre. The classic causes are opening the oven early, which drops the temperature at the moment the structure is still liquid; underbaking, so the centre never sets at all; and too much leavener, which inflates the batter faster than the protein and starch can build something to hold it.
The last is the least intuitive and the most common. More baking powder does not make a taller cake — past a point it makes a cake that rises spectacularly and collapses, because the gas outruns the structure.
Related
Part of
The cake family’s reference product.
What this product needs done
Structure building
Egg protein setting, with gelatinised starch alongside it. Gluten is actively unwanted, which is why sponge recipes call for a soft flour.
Aeration
THE DEFINING REQUIREMENT. A sponge is raised by air beaten into egg or into creamed butter and sugar. A chemical leavener may insure it and does not replace it.
Gas retention
A batter viscous enough to hold the foam it was given until the protein sets.
Hydration
Egg and milk supply it. A sponge batter is poured, and it needs enough liquid to pour.
Gluten inhibition
Fat and sugar both restrain gluten. A sponge with developed gluten is bread.
Techniques this product depends on
A sponge is raised by air beaten into egg. Owning eggs is not owning a foam, and a sponge whose eggs were stirred rather than whisked is a flat, dense cake.
The flour is folded into the foam, not stirred. Stirring collapses the air that is doing the lifting.
Techniques involved
A sponge is baked in a tin and a sponge that tears on release has lost the structure it had. The fault is in the preparation rather than the formula.
A creamed sponge depends on butter in a plastic state. Butter melted to hurry it along cannot hold air, and the cake rises less however long it is beaten.
Things that go wrong
An egg-free bake came out dense or gummy
The product where this fails most reliably, because a sponge’s lift IS the whisked egg.
Where a dry crumb is most obvious, because a sponge has the least fat to hide it.
Meringue is weeping, chewy or will not whip
Whisked egg-white foam is the same mechanism a sponge depends on, and it fails the same way.
The cake is dense and did not rise
Recorded because the V3 demand asks about this fault under this product name, not because the fault belongs to it alone.
The cake is raw, wet or gummy in the middle
A shallow cake makes this rarer and it still happens with a cool oven.
The reference creamed cake, and the family the model was written from.
The cake domed and cracked on top
A shallow cake domes when the oven runs hot, which is the clearest single signal of it.
Layer cakes show oven unevenness more visibly than anything else.
Covered in
The cake families, sorted by how the air gets in
The foam family, where the whisked egg IS the leavening.