In the last post, I looked in detail at creaming the butter and sugar, the starting point for many cakes. This post follows what happens next – adding the eggs, flour and then baking.
I found a great description of what happens in a cake in Rose Levy Berenbaum’s Cake Bible:
“Ingredients fall into two categories: those that form and strengthen the cake structure and those that weaken it”.
The flour and eggs provide the protein that holds the cake structure up, and stop it from collapsing into a pancake. The fat, sugar and leavening all weaken the structure in different ways, making the cake tender and soft instead of tough and chewy. The balance between the two sides is important for capturing the air that makes cakes soft and light.
Adding eggs – what happens when it curdles
Almost as soon as I put the last post up, someone asked what happens if the mixture curdles. I have looked into this problem before – most people seem to say it can be avoided, perhaps marginally reduces the volume of the final cake, but if it does happen, you can carry on without problems.
But what was unclear was what caused it to curdle in the first place – was it really not enough creaming, or something else?
When the mixture curdles, what you see appearing are lumps of fat and sugar, surrounded by a thin watery liquid. The clearest explanation I found came from Shirley Corriher in ‘Bakewise’. She describes this as a:
“switch from the the water-in-oil emulsion that you want to an oil-in-water emulsion”.
This probably only makes sense if you know what an emulsion is. An emulsion is simply one liquid suspended in another. In this case, when you start to add the eggs, you are aiming for little droplets of the water from the eggs, suspended through the fat-and-sugar mixture that is already there. At some point, the liquid from the eggs can overwhelm the amount of fat, causing the bubbles of water to all join up and become the main part of the mixture – the continuous phase, as it’s called.
To prevent this happening, you need to ensure that the fat and sugar are able to hold as much liquid as possible – which means soft, but not melted. You also need to add the egg very gradually, so that it doesn’t overwhelm the mixture. This is the same principle as adding oil to mayonnaise – go slowly and incorporate each bit before you add some more.
Finally, the solution once it has curdled – which it might well do – is to stop beating it and add some flour. This will absorb the excess liquid that’s starting to pool, and shift the balance back again.
Speaking of Shirley Corriher, this is a brilliant excuse to link to my favourite food science programme, Good Eats:
Good Eats: A Cake on Every Plate
Shirley appears at about 4m30 (disturbingly extolling the virtues of cake flour, which you can’t get in the UK because it’s chlorinated, and the EU aren’t big fans of that idea).
Alton also talks about creaming and bubbles at about 8m30. He also has kick-ass flames painted onto his KitchenAid mixer.
Once the eggs are in, the final step is to add the flour, and any liquid that might be called for. These are often added in alternate batches, so that the mixture gets neither too stiff nor too runny as they go in – either might deflate the air.
An often neglected step is to thoroughly sift the flour and baking powder together. This isn’t necessary if using self-raising flour, but when adding baking powder, there is always the risk that small lumps of leavener will persist in the batter, and produce large ugly holes in the final cake. If you really want a fine texture, sift two or three times before it goes into the batter.
The other important thing when you add the flour is to stop folding or stirring as soon as the flour has disappeared into the mixture – don’t mix any more than you need to. As soon as the flour makes contact with the liquid in the eggs, and any added liquid like milk, it will start to make gluten. The more you mix at this point, the longer and stronger the gluten will become, and the tougher your cake will be.
The final point is on baking. The balance here is between allowing the leavener time to work and expand, and setting the egg and flour proteins in a structure that will hold the air. Bake at too high a heat, and the leavener might not have had time to work before the batter sets, making a more dense cake with a closer texture. Bake at too low a temperature, and the gas might bubble to the surface and disperse, and so be lost that way. A medium temperature will set the batter at the right point, and bake through evenly without making the surface too dark and brown.
An alternative method – the two stage approach
When consulting Rose Levy Berenbaum, I discovered that she actually doesn’t recommend creaming at all. Her favoured approach is a different one completely. She combines the flour, sugar and fat together with a little egg, and beats thoroughly to incorporate air. Then she adds the remainder of the egg, and other liquid in batches.
This approach takes a different route to the issues above. By combining the fat directly with the flour, it can be coated to prevent the liquid getting at the protein and forming gluten. The flour-sugar-fat mixture can still hold air, so the creaming still generates volume. And the eggs are added only once the flour is already there to absorb liquid, so there is no risk of curdling.
I haven’t tried this approach more than once or twice, but I will be trying it out alongside regular creaming to see what effect it has. Watch this space.