Culinary foams consisting of natural flavors mixed with a gelling agent such as gelatin, lecithin, or agar.
Chefs have been making different types of foam since the dawn of time. Whipped cream, meringues, soufflés, mousses and marshmallows all qualify as they each have a unique “foamy” light texture and mouthfeel due to the tiny air bubbles incorporated during mixing. More recently, culinary foams have become a part of molecular cooking techniques made famous by adventurous chefs who are incorporating more science into their cooking styles. (Read more about molecular gastronomy here.)
Culinary foams are created with rich base flavors like stock, fruit juices, and vegetable purées. These are combined with neutrally-flavored stabilizing or gelling agents for superior holding power, preventing ingredient breakdown later on and aiding to the foaming effect.
The scientific process of “foaming” can get very techy with details of emulsions and shearing power, surfactants (binding agents), interfacial tensions between liquid and gas phases, etc. Simply put, to create the ethereal foams of master chefs you’ll need to do a little research into foaming agents and experiment in the kitchen to determine which one will work best with your flavor base and which one will achieve your desired textural effect.
The three main binding agents are gelatin, lecithin, and agar.
Gelatin is a very efficient foam stabilizer (remember the marshmallow). Gelatins turn liquids into solids, and because they are flavorless keep fresh flavors intact without diluting them as fats can. Gelatins are derived from seaweed, animal proteins, fruit pectins or vegetables. Different gelatins have different foam stabilizing properties and gelatin for this use needs to be carefully selected.
Lecithin is classified as an “amphoteric” binding agent in that it can react with either an acid or a base. It is ideal for converting juices and watery liquids to airs and foams. To produce a stable foam, start with a ration of .6% of lecithin.
Agar is a gelatinous substance derived from seaweed. Though chiefly used as an ingredient in desserts throughout Japan, many chefs worldwide are now experimenting with agar as it’s a good vegetarian alternative (Read more here).
Finally, some air is introduced into these base and binder mixtures via whipping. Foams made with the use of a hand-held immersion blender results in a delicate froth like that found in cappuccino. For denser foams, chefs reach for a cream charger gun or espuma (Spanish for foam) gun specifically designed for this task which uses gas canisters of N2O (Nitrous Oxide) for bubbly results.
So simply take your super flavorful base, add a binder and whip in air to create unique textural and visual foam aspects to your dishes.