espumas

Espumas, or foams, are materials in which a dispersed gas forms bubbles within a continuous phase. They can be liquid foams, where gas bubbles are dispersed in a liquid (as in beer, whipped cream, or the froth on beverages), or solid foams, where gas is trapped in a solid matrix (such as polyurethane, metal, or ceramic foams). In culinary contexts, espumas refer to light, aerated foams produced from flavored liquids, often stabilized by proteins or hydrocolloids.

Foams form when gas is introduced into a liquid that contains surface-active compounds, which lower interfacial tension and help create stable bubbles. Stabilization is aided by emulsifiers, proteins, polysaccharides, or gels that increase the viscosity and create a viscoelastic interfacial film. Common culinary stabilizers include lecithin, gelatin, egg white proteins, xanthan gum, and agar. Foaming methods include whipping, emulsification with siphons charged with gas (nitrous oxide or carbon dioxide), and ultrasonic or high-shear processing.

Key properties include bubble size and distribution, porosity, drainage, and coarsening. Stability depends on interfacial film strength, continuous-phase viscosity, temperature, pH, and additives. Some foams are long-lasting, others transient.

Applications: In gastronomy, espumas add texture and aroma to dishes. Industrial foams provide cushioning, insulation, packaging, and acoustic damping; examples include polyurethane foams, metal foams, and ceramic foams. Environmental and safety considerations arise with certain blowing agents and production processes.