ABSTRACT
Cake batters are a complex mixture of numerous air bubbles and dispersed fat particles in a continuous aqueous phase. The batters can be divided into two categories, those with high and low fat content. In batters with high levels of fat, the air is predominantly beaten into the fat phase, thus creating an unusual system where the foam is trapped inside the emulsified fat phase which is then mixed into an aqueous phase. In low-fat or fatless batters, the air is occluded directly into the aqueous
phase and thus forms a conventional liquid foam. The dispersion of air and fat generates considerable area in terms of gas-liquid and liquid-liquid interfaces, and these newly created surfaces have to be stabilized to prevent the dispersed phases from reuniting and separating out of the aqueous phase. During baking, a further increase in interfacial area occurs as a result of bubble expansion, and this area also has to be stabilized to prevent bubbles from coalescing and impacting on cake quality. Interfacial properties therefore play a crucial role in both the batter and the baking stages of cake production. This chapter reviews in brief a number of the chemical and physical properties of surface-active materials and explains some of the functional roles that are relevant to cake emulsion systems. The type of improvements required from surface-active materials are discussed, and the ways these improvements are brought about are explained. The production of surface-active materials in situ by the use of enzymes is specifically covered.
