Last year [= last week] I was writing about baking powder. Even as I wrote ". . .there are two ways of getting loft into cakes - biological and chemical . . ." I knew I was ignoring part of the cakiverse. So here I am making up for slighting the physical / mechanical ways of creating foamy deliciousness. During my expensive education, I tried a few things once and then moved on.
- I was in a play that had a morris dancing scene;
- but not the other Beecham thing(*);
- I made a cheese soufflé;
- I rode a donkey . . . for 15 seconds
- I went pillion on a motorcycle . . . for 15 minutes
You can tell I've lived a very exciting life; but the only event relevant to this post is the soufflé, which derives its light airiness from beating egg whites to a foam and folding that gloop gently into the other ingredients just before baking - pre-heat oven, or the confection will collapse.prev].
- Don't use a plastic bowl: it is hard-to-impossible to clean oils from plastic. Oils and fats prevent the egg-white proteins making the crucial interface between air and water.
- rigorously exclude egg-yolk: lecithins are complex fatty molecules which are even more effective than sunflower oil or residual butter at elbowing into the molecular edge of the bubbles and causing collapse.
- salt is ionic and will change the shape of albumin and lower its foam making capabilities - if you must add salt to taste, do so at the last moment
- also add sugar [folding in] after the egg whites are proper peaky.
- a pinch of cream of tartar [tartaric acid as in baking powder prev] will lower the pH from 9 to ~8 and this seems to enhance the foaminess and stability
- it has long been asserted that a copper pan is a miracle-worker for meringues and there is some scientific evidence that copper ions help prevent over-beating collapse by stabilizing the foam
- before your eyes evidence for bowl effects
So there is a little chemistry in making great meringues, but it's mainly elbow work [or Kenwood Chef for wimps].
Victoria sponges are related. Cream butter and sugar till it turns white [ie gorra lorra air in], in a separate bowl whisk the eggs so that they also have a lot of incorporated air. Throw them together then g e n t l y fold in sufficient flour; taking care not to work all the air out by over stirring. Very similar in principle to a soufflé, as both rely on beating to create bubbles in a foam and ultimately in the finished product. You'd be surprised by strawberry jam and clotted cream in a soufflé, though.
*Sir Thomas Beecham once said "In this life try everything once, except morris-dancing and incest".