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Foam

Foam. A two-phase gas and liquid system in which minute gas bubbles or air cells, representing the disperse phase, are surrounded by liquid films that comprise the continuous phase. In baking, familiar examples of true foams are beaten egg white (q.v.) and whipped cream (q.v.), while aerated batters (q.v.) and doughs may also be considered as representing special types of foam. The ability of a liquid to form a foam depends on its viscosity (q.v.) and on a low air-liquid interfacial tension (q.v.).