Foam is to early-21st-century dining what balsamic vinegar was to the 1990s: It is everywhere, and often for no particular reason.
The fad started at experimental restaurants, where technically oriented chefs marveled at their ability to make sauces that were so light as to seem suspended above the rest of the dish. As the methods spread, even chefs with little or no interest in the science of cooking followed suit. Suddenly, cream siphons were a must-have. Thickeners such as lecithin, xanthan gum and agar, long used in the food industry, became kitchen staples. Foams helped diners appreciate the unbearable lightness of eating.
To some critics, foam is the symbol of all that is wrong with “modern,” “modernist” or “molecular” cooking. Foam is full of gas, they say, with no substance, metaphorically as well as literally. Its only function is to show that the chef is modern, and desperately trying to capture the culinary zeitgeist in his siphon. Culinary foam has become a cliche: little of it on top of a scallop is expected, not surprising.
But remember: Foam was not built in a day, and certainly not in a lab-like kitchen over the past 15 years. It has been a part of what we eat for centuries, if not millenniums. The modern foams are just a handful of new recipes to add to a plethora of old ones.
Foam is bubbles — gas — enclosed in, well, more or less anything. It can be protein, fat, gel or even a solid or semi-solid substance. Steamed milk is foam. That foam is, like the bubbles that form on top of your pot of boiling stock, protein-based. Whipped cream is a different type of foam, based on fat. Then there are foams based on starch, or created by the viscosity of a liquid. (If it is thick, it takes a long time for gas to escape.)
The realization that most people eat foam in one way or another every day might be a humbling reminder for the worshipers of modern foam: What you are doing is not so new. Even if the foam stabilizer you use has been on the market for only a few years, the mechanism behind it is more or less the same as the old-fashioned foams. It might also serve as a reminder for the detractors of foam: Yes, to worship foam is folly. And not every scallop dish requires it, or even benefits from it. But to declare that you dislike foam wholesale is to declare that you dislike everyday items such as cappuccino, whipped cream and bread, and treats such as souffle, spongecake, milkshakes, meringues and the bubbles on top of a glass of just-poured champagne, without which life no doubt would be a sadder, flatter place.
I think the problem is that we tend to forget the craft that lies behind the old foams. A few years ago, I was touring the country promoting a book on Scandinavian cooking. For most television appearances I chose to make what was certainly one of the simplest recipes from my book: Veiled Farm Girls, a traditional dish consisting of layers of whipped cream, applesauce and cinnamon-toasted bread crumbs. I chose it because it was simple and foolproof. But I was shocked by how often I heard comments about the cream.
“Did you really whip the cream yourself? Well, my grandmother did that, too!” one television host told me proudly, as if whipped cream were a thing of the past.
“What do you do instead?” I asked. It turned out that she used Cool Whip, a modern edible foam from the food industry. It is not highly regarded by modernists (or by anyone else with interest in high-quality cooking), but the idea is similar: using technology and additives to achieve new textures and to obtain a predictability that traditional methods cannot offer.
The old foams demand two things a cream siphon does not: a constant presence from the cook, and an ability to respond to the food as you’re cooking. When making zabaglione, whipped cream or steamed milk (all three are combined in my coffee zabaglione on Page E8), you have to interact with the food in a way that is almost impossible to master. And even if you do master it, things can always go wrong.
It is very difficult to measure the perfect temperature of a zabaglione while you are making it, for instance; the egg mixture should begin to set, but if you heat it too much, you begin to scramble the eggs, and the zabaglione becomes grainy and starts to collapse. The process can be controlled by precooking the egg yolks by the sous-vide method to around 157 degrees, but do you want to start up an immersion circulator just to make zabaglione? Finishing it in a cream siphon, which injects the mixture with nitrous oxide to create the foam, is convenient if you are in a restaurant kitchen, but hand-whisking creates a livelier foam.
With whipped cream, the challenge is to whisk it enough to create soft peaks but to stop before it starts to turn into butter. The cream needs to be at least 35 percent fat in order to whip, and its temperature is critical. If the cream reaches 69 degrees or higher, it will be impossible to whip it into shape. That is why it can be difficult to make whipped cream in summer; even if the cream is cold, the bowl, whisk and surrounding air are often significantly warmer. (That’s why your grandmother may have taught you to leave the bowl and the whisk or mixer blades in the freezer for a few minutes before whipping cream. You should also consider doing the job in another room; the kitchen usually is the warmest room in the house.)
To make cream more stable, give it a hot-cold treatment (as described in Nathan Myhrvold’s “Modernist Cuisine”): Heat the cream to 86 degrees and hold it there for about 30 minutes, then cool it to 41 degrees before whipping. Even easier is to add a little gelatin in the form of a melted marshmallow, quickly beaten into the cream after it forms soft peaks.
The simplest way to make foam is so efficient that it’s strange that is not used more: Place one egg white into a very clean mixing bowl. Add white wine or porcini consomme or anything liquid and nonfat, and whisk. That one egg white has the ability to create around one gallon of foam, more than most special equipment is able to.
But why foam in the first place? Why adulterate the food you eat with the air you breathe?
When used correctly, foam can transform and enhance food. Just as we have trouble differentiating between sounds if we are exposed to a continuous stream of noise, so it is when we eat; the small bubbles in the foam give our senses tiny breaks that allow us to perceive the food more acutely.
I don’t want to eat a teaspoon of cream, which feels too heavy, but a tablespoon of whipped cream feels light and makes me want more. When you add whipped cream, a green pea soup (Page E8) tastes sweeter and more like itself, more like peas, in part because of the many bubbles. And if you add a splash of sparkling wine at the last minute, you are not just adding more gas and the taste of the wine, but also the perception that your soup is alive.
That’s an old-fashioned decadence that makes a traditional dish taste fresh and new.