Preparations as sponge cake belongs to the so-called category of “whipped batters”. This family is rather wide and includes, in general, all those batters that are beaten in order to incorporate air. These batters are commonly used as bases for more complex preparations as multi-layers cakes, Sacher, angel food cake…
From the scientific perspective, these batters are whipped emulsions and, therefore, foams...a colloid in the colloid :) The inclusion of air allows the batter staying fluffy. Indeed, very often these preparations do not require any rising agent.
How can we make sponge cakes and similar foodstuff?
1. Preparation of the batter. That includes eggs, weak flour and sugar. Sometimes, other ingredients as shortening, backing powder, cocoa or almond flour are added to the batter.
2. Whipping. The batter is whipped manually or with an electrical whisker in order to incorporate air. The mechanical action denatures the egg proteins, which help stabilizing the foam, as already discussed in this post.
3. Baking. During this step, air bubbles expand, while the egg and flour proteins coagulate and trap the air bubbles. The expansion of air bubbles is limited by the viscosity of the batter. The equilibrium among those two forces, air expansion and viscosity, is crucial for a good outcome.
Now that our sponge cake is ready, we can use it to prepare puddings, multi-layers cakes, Sacher or other yummy desserts :D
This was a brief introduction. There are still a lot of things to take into consideration as all the factors involved in the stability of sponge cakes & co. But we will see that next week :)
The next appointment is on Thursday, for a sweet, indulgent recipe ;)
Leonardo di Carlo, Tradizione in Evoluzione, 102-103, Chiriotti Editori
D. Elgeti et al., Foam stabilization during processing of starch-based dough systems, Innov. Food Sci. Emerg. Technol., 2017, 39, 267-274