froths

Froths are foams formed when gas bubbles are dispersed in a liquid or solid matrix, creating a floating layer of tiny bubbles. They are typically composed of a continuous liquid phase with gas-filled bubbles separated by thin films. Stability arises from surface-active compounds that reduce surface tension and form a stabilizing film around each bubble; proteins, phospholipids, and certain surfactants are common contributors. Froth structure is influenced by bubble size distribution, drainage of liquid from the films between bubbles, and phenomena such as coalescence and Ostwald ripening, which can make a froth rise and then collapse over time.

In culinary and beverage contexts, froths contribute texture, aroma, and appearance. Milk froth is produced by aerating milk with steam or whisking, with proteins and fats helping stabilization. Beer and sparkling wines form a head of foam due to surface-active components and carbonation. Egg foams (meringue), whipped cream, and some mousses are intentional foams created by whisking or whipping, using proteins like ovalbumin or milk proteins to trap air.

In industry and the environment, froth-based processes include froth flotation, a mineral-processing technique that uses air bubbles to separate hydrophobic particles. Foaming can also occur in wastewater and industrial detergents, sometimes requiring antifoaming agents to prevent equipment issues. Sea foam and foam produced by waves result from the agitation of seawater containing organic matter and salts and are not necessarily linked to surfactants.