Traditionally foams have always formed a part of the pastry chef’s repertoire. Whipped cream and meringues are just two examples. Air is whipped into a liquid, either heavy cream or egg whites, and the result is a frothy set of stabilized bubbles. They hold up fairly well at room temperature and both are strong enough to be piped through a pastry bag. But what about foams with no fat—with strong clear flavors?
Foams as a Sauce Alternative
Foams can take many forms, but in all cases they are a liquid composed of a multitude of bubbles. The stability of these bubbles is what will dictate the ultimate form and look of the foam. The simplest form of a foam is made by incorporating air into ice-cold whole milk. The result is a foam with large light bubbles. The bubbles resemble soap bubbles. They are clearly delineated from each other.
Heat milk to infuse desired flavors. Allow to steep if needed. Chill milk until icy cold and then vehemently whisk when needed for service. The resulting bubbly foam can be spooned off the top of the milk and placed on the plate as a sauce. These bubbles have a short life span and will dissipate quickly. The large, clear bubbles resulting from aerated foam offer a beautiful visual contrast both on the plate itself and on the palate. They give texture to sauce work and are light and airy on the tongue. Such foams will work as top notes.
A light foam is not always desired. Sometimes the chef wants a foam with smaller bubbles, a foam that will not dissipate so quickly on the plate or on the customer’s tongue.
Foam ISI Canister
Since foams are simply aerated liquids, the smaller and tighter the bubbles, the heavier and more stable the foam will become. An ISI canister pumps gas into a liquid base and is one way of creating small bubbles out of a liquid. The resulting foam is much more tightly packed than a simpler hand aerated foam. An ISI foam can be piped and will still hold its shape. Although the ISI canister has traditionally been used to make whipped cream, fat-free intensely flavored waters, juices, and liquors can also be used with great results.
Foams stabilized with gelatin are quite strong. They will hold their shape for a long time, which allows them to be made before service. Additionally, such foams can be scooped and frozen. The following method of preparation is based on the fact that as bloomed and dissolved gelatin cools, it begins to thicken. (For exact measurements see the Appendix.)
Prepare the liquid. Some options include infusing water or dairy and lightly sweetening. Take approximately two-thirds of the liquid and place in a freezer. The liquid must be icy cold to achieve the best results. Storing the liquid in a metal container will facilitate the cooling process. Rehydrate or bloom the gelatin sheets by covering them with cold water. Wring out the excess water. Heat the remaining one-third of the liquid; add the rehydrated gelatin. Stir to dissolve gelatin. Place the gelatin mixture in a 5-quart KitchenAid mixer with the whip attachment. Start the mixer on speed 3 and slowly drizzle in the remaining two-thirds of icy cold liquid.
The theory behind this foam is simple. The addition of the icy liquid to the warm gelatin mixture means that the gelatin will start to solidify or to set up. By whipping the mixture on speed 3, the gelatin is being broken up into tiny pieces as it chills. The result is a foam with relatively small, yet clearly visible individual bubbles. It is extremely stable and will remain stable for quite a while. The mixture will continue to gel and solidify as it sits out at room temperature. For a clean look on the plate, simply scoop or quenelle the foam onto a parchment lined sheet pan and hold for service.