A foam is a dispersion of gas bubbles in a liquid or semi-solid medium, stabilised by a network of protein, fat, or surfactant molecules at the gas-liquid interface. The kitchen's foams — whipped cream, meringue, bread's crumb, beer head, the mousse — are all governed by the same physical principles. Understanding foam stability — why some foams last and others collapse — allows the cook to design the texture rather than accept it.
Modernist Cuisine