In a cake sponge, air is entrapped in a solid network of fat, starch and proteins.
During batter making, ingredients are mixed and air is incorporated into the system.
The mixing process breaks down the fat particles into smaller ones, forming an oil-in-water emulsion, mainly stabilised by egg yolk proteins. Meanwhile egg white proteins and solid fat crystals stabilise the air bubbles.
During baking, the rise in temperature causes expansion of the air bubbles and melts the fat crystals, inducing starch gelatinisation and protein coagulation, setting the cake structure.
Anne Vissers, senior bakery scientist, Campden BRI
Campden BRI provides technical support to the food, drinks and allied industries worldwide. Its activities are built on a programme of industrial relevant research and innovation steered by industry. See campdenbri.co.uk or telephone 01386 842000