Recap

• Latte art has a 26-year history, but references to milk mixed with coffee go back more than 300 years.

• Milk is approximately 87% water.

• The other 13% is mostly made up of sugar (lactose), fat, and protein.

• Casein protein helps as an emulsifier.

• Whey protein helps stabilise milk foam.

• When entraining air, it’s helpful to add the air before the milk gets hot and to increase the volume of the milk by 33%.

New Words

Emulsifier  A surface-active substance that helps stabilise an emulsion.

Entraining  The process of injecting air into the body of a current of liquid in a way that holds it in suspension

Latent heat  Energy that is absorbed or released by a substance as it changes phase (e.g., from a gas into a liquid)

Macrobubbles  A foam made of large bubbles; in a latte foam context, bubbles greater than 0.5 mm in diameter are undesirably large.

Microfoam  A foam comprised of very small, uniform-size bubbles having a diameter usually less than 500 um

Surfactant  A ‘surface active agent’ which lowers the surface tension between substances; surfactants are integral to the performance of detergents, wetting agents, emulsifiers, foaming agents, and dispersants.