Foam: An Introduction
Foams, if you’ll pardon the pun, are the whipping boy of avant-garde cuisine. Those who fear “molecular gastronomy” deride them; those who practice it often downplay them. Anthony Bourdain once famously derided the godfather of avant-garde cooking, Ferran Adrià, as “that foam dude.”
So what exactly is a foam? At the highest level, it’s a dispersion of a gas in a liquid or solid, in the form of tiny bubbles. Because these bubbles interfere with the movement of the liquid phase, a foam is, perhaps counterintuitively, thicker in texture than the fluids it’s made up of. Different foams have different levels of stability: some are fleeting, needing to be eaten moments after they’re created, while others will last indefinitely. Foams collapse as the liquid in the bubble walls drains downward due to gravity; you can stabilize them by thickening the liquid, which makes it drain more slowly.
Although the term is currently associated with avant-garde cuisine, foams have been a mainstay of Western cooking since well before Adrià: for example, the steamed milk shown above is a type of foam, as are meringue, sabayon, whipped cream, and even bread. Many foams exhibit a couple of properties that make them useful in culinary applications. Because they have copious amounts of surface area, aroma molecules can easily escape, giving them great flavour release; at the same time, their relative fragility gives them a pleasing light-as-air texture, as they dissipate in your mouth. Foams have been around for a while and, like it or not, they’re here to stay.
Are you pro-foam or anti-foam in your food?