frothing

Frothing is the formation of foam or froth on a liquid, typically by introducing gas bubbles into the liquid so that a thin liquid film surrounds each bubble. Froth consists of a dispersed gas phase within a continuous liquid phase, and its stability is often enhanced by surface-active compounds (surfactants) or by the physical properties of the liquid. Frothing occurs in culinary, industrial, and scientific contexts, producing foams that can range from light, temporary bubbles to dense, long-lasting foams.

Its behavior depends on interfacial surface tension, liquid viscosity, bubble size, and drainage of the liquid films that separate bubbles. Agitation, aeration rate, temperature, and the presence of surfactants or dissolved salts influence both foam formation and stability. When bubbles are small and surface films are durable, foams tend to be stable; if films drain rapidly or coalesce, the foam breaks down quickly.

In kitchens, frothing is used to create milk foam for coffee drinks, steamed milk, and whipped toppings, with factors such as milk composition, temperature, and aeration method shaping foam texture. In industry, froth formation is central to froth flotation for mineral separation and to the use of foams in firefighting and insulation. In many processes, controlling foam formation is important to efficiency and safety.

Foaming and defoaming are managed with stabilizers or antifoaming agents to promote or suppress froth as required. The term frothing is sometimes used interchangeably with whipping or aeration in culinary contexts, though whipping typically yields a more vapor-rich, airy emulsion.