|Liquid Nitrogen: Fun with -320°F
It’s clear, odorless, tasteless, and it freezes foods at lightning speed. Chances are you’ve seen ice cream, sorbets, or even frozen cocktails emerge from its swirling mists. Liquid nitrogen is an undeniably fun kitchen toy—but more than that, it’s a useful tool for creating a slew of cool (pun intended), unusual textures.
Ice cream is a good place to start. The extreme cold (-320°F, to be precise) means that the liquid freezes so quickly that ice crystals don’t have time to form, making for an especially smooth, creamy texture. Once you’ve got the technique down, that is. When Janine Falvo of Carneros Bistro & Wine Bar first started playing with liquid nitrogen, she added too much to the bowl holding her popcorn crème anglaise and started scrambling the mixture as you would an egg. The result was popcorn-like nuggets—not the smooth ice cream she was hoping for, but an altogether different texture. But as it turns out, the happy mistake found its way onto her menu as “frozen popcorn,” served as an intermezzo or aside a chocolate tart.
At Madrona Manor in Healdsburg, California, Chef Jesse Mallgren serves a classic ice cream sundae, with one small twist—the ice cream is “hand churned” tableside, with the help of a smoking bowl of liquid nitrogen. Mallgren was inspired by the bacon and egg ice cream made tableside at The Fat Duck, Heston Blumenthal’s restaurant in Bray, England. “It’s interesting theatrics,” says Mallgren. “I thought I’d play with that and see if we could make it more American. The texture is so amazing—it’s custardy, very smooth, almost like a crème brulee.”
The idea isn’t really new. Blumenthal cites a Victorian cookbook writer named Agnes B. Marshall, whose 1885 “The Book of Ices" suggests letting guests at a dinner party make their own ice cream with a bowl of liquid nitrogen. Nor is it limited to the restaurant world: Blue Sky Creamery, available in grocery stores around the country, freezes their ice cream using liquid nitrogen. The rapid freezing eliminates the need for eggs and extra butterfat, they say, which help to make conventionally frozen ice cream smoother and creamier. In Chicago, the recently opened iCream Café in Wicker Park uses KitchenAid stand mixers and liquid nitrogen to make customers’ personalized ice cream creations in mere seconds.
A New York Times article from July 11, 1961 holds an interesting liquid nitro technique idea. While testing liquid nitrogen as a method for freezing food, an employee of the Air Reduction Company dropped a frozen orange segment: “…and it shattered into thousands of tiny juice cells. The cell walls remained unbroken, retaining full flavor and making the crystals ideal as flavoring agents.” Shattering can be used to separate individual citrus cells for garnishes, or for breaking larger fruits and vegetables into artistic, abstract shapes—technique used by Aki Kamozawa and H. Alexander Talbot, the duo behind industry blog Ideas in Food.
The two also use it to make frozen banana powder. They freeze the banana in liquid nitrogen until solid, and then blend it until it’s turned into a fine powder. “This light, frozen powder can be scooped up like snow and once eaten melts quickly into a rich stream of banana goodness sliding down into your tummy,” they write. “Powdered frozen bananas, try them and you'll never go back to bananas on a stick.”
Falvo does the same with cheese—freezing and grinding it to a powder—so that when it hits the warmth of a diner’s palate, it coats the tongue like melted cheese. She also makes olive salt by freezing olives in liquid nitrogen, grinding them, blending them with salt, and dehydrating the mixture in the oven.
In the last year, both Dani Garcia (of Calima in Marbella, Spain) and Ferran Adrià (of el Bulli) have demonstrated freezing a spoonful or small ball of puree in liquid nitrogen so that the outside is a thin frozen shell, and the inside is still soft and warm.
Liquid nitrogen is often delivered and stored in dewars—insulated, vacuum-jacketed pressure containers specially engineered to release pressure buildup and prevent explosions. Store your dewar in well-ventilated areas (many companies have regulations about where and how it needs to be stored)—and don’t be too gung-ho about doing anything with your bare hands. Injuries from liquid nitrogen can range from a brief tongue burn if something is eaten too cold (think tongue sticking to a cold metal pole) to serious tissue damage from the cold, so don’t pour the liquid nitrogen too quickly or pop something just-frozen into your mouth. Another obvious but necessary tip: It’s compressed gas, so keep it far, far away from open flame.
As for the basic ice cream technique, the consensus is that it takes a few tries before figuring out the motion, pace, and quantity that you like best. As a rule, stir slowly and add the liquid nitrogen slowly for the best (smoothest) results. Use a wooden spoon, as a metal spoon will get too cold, and whisking will make it clump.