In the food world, culinary foam consists of gelatin (or other gelling agent) mixed with a liquid (from cream to water to wine) and other flavorings, which may be herbs or spices or any of myriad puréed ingredients (such as berries, fish or potatoes). The savory or sweet blend is placed in a whipped cream dispenser fitted with a nitrous oxide (NO) cartridge, which forces the mixture out into a froth. Such foams are the inspiration of Ferran Adrià, innovative chef of El Bulli in Roses, Spain, one of the world's premier restaurants. Foams may be used as a base to a presentation or as a topping.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.