Long sleeves. Check. Goggles. Check. Safety gloves. Check.
Liquid nitrogen hisses and boils violently as it's poured into the bowl of a stand mixer, erupting into a 360-degree wave of vapour that ripples through the room. When the fog clears, it has transformed a vanilla custard into the silkiest ice cream imaginable, all in the confines of a home kitchen.
Molecular gastronomy chefs first recognized liquid nitrogen's potential to create stellar ice cream years ago. Michelin three-star wunderkind Heston Blumenthal of The Fat Duck in Bray, England, has a famous bacon-and-egg variety. In Canada, servers craft dishes of liquid nitrogen crème fraîche ice cream tableside at Toronto's Colborne Lane.
But while many molecular gastronomy innovations never migrate beyond professional kitchens, this is one technique resourceful cooks can use at home. And it's not just for show. Liquid nitrogen enhances one of ice cream's signature qualities: texture. "People are looking for creaminess," says David Lebovitz, a veteran of the pastry department at the legendary Chez Panisse and author of The Perfect Scoop: Ice Creams, Sorbets, Granitas, and Sweet Accompaniments.
Taste is still paramount - people ceaselessly bicker about the superiority of one flavour over another. But chocoholics and vanilla junkies almost unanimously prefer ice cream that has a smooth consistency and rich mouth feel even after the carton has been pulled from the freezer a dozen times. That's why most store-bought ice creams contain a long list of unpronounceable emulsifiers and stabilizers such as mono- and diglycerides, guar gum and carrageenan.
It wasn't always so. Back when ice cream was a down-home affair made with ice, salt and elbow grease, a little coarseness was expected, even appreciated. But with industrialization came palates that craved ever-more-refined results. "Dense," "smooth" and "creamy" became buzzwords for this ideal texture.
Of course, this emphasis on texture gave mass producers, with their specialized additives and blast freezers, an advantage over home kitchens equipped with only basic ingredients and chill chests set to a relatively balmy -18 C.
Liquid nitrogen not only levels the playing field - it tilts it in the home cook's favour. At the microscopic level, ice cream is ice crystals surrounded by chilled cream and air. Small crystals equal smooth ice cream, and they require rapid freezing. That means mind-bogglingly cold temperatures.
Enter liquid nitrogen.
As noted food science writer Harold McGee, author of On Food and Cooking: The Science and Lore of the Kitchen, explains: At -196 C, the temperature of liquid nitrogen, "water molecules are essentially frozen in place and end up being immobilized in tiny aggregates, mini-crystals, and so you get this wonderful creamy effect."
It may sound extreme, but making liquid nitrogen ice cream differs very little from the traditional ice-cream-making process familiar to home cooks. The base is exactly the same - a blend of dairy, sugar and sometimes eggs, with a flavouring - but it's frozen by slowly stirring liquid nitrogen into it using either the paddle attachment of an electric stand mixer or a wooden spoon and some muscle.
The result? Liquid nitrogen produces "unequivocally the best ice cream I've ever had," says chef Claudio Aprile of Colborne Lane. It's a position he defends by pointing to his work with scientists who have "PhDs in ice cream technology" - and objective experience.
"Do a blind taste test," he argues, "and let it be the deciding factor." Then he brandishes a bowl of lemon-zest-dappled crème fraîche ice cream - fashioned à la minute with some liquid nitrogen and a wooden spoon - that melts into a silky ribbon on the palate.
All that creaminess comes at a cost: Renting the dewar (the thermos on steroids in which liquid nitrogen must be stored) and buying five to 10 litres of liquid nitrogen (the minimum amount most vendors will sell) runs from $50 to $100, plus deposit.
So your homemade ice cream won't come cheap, considering it takes about an equal volume of liquid nitrogen to transform a litre or so of base into a slightly greater volume of ice cream.
There's also some risk. Liquid nitrogen must be handled with at least as much care as hot fat. Proper storage, goggles and gloves to prevent burns and eye injuries are essential, as is a well-ventilated kitchen to prevent oxygen deprivation that can, in extreme cases, cause death.
But it's hard to beat the quality - and the spectacle. Mr. Aprile's decision to make ice cream in front of customers may seem like gimmickry, but only because it highlights liquid nitrogen's other great advantage: The wow factor.
"The little bit of tension at the table when this little mystery bowl comes up that's smouldering is very appealing."
Special to The Globe and Mail
Malted Milk Ice Cream
Those who love their ice cream dense and creamy will have a hard time beating this recipe, adapted from The Perfect Scoop: Ice Creams, Sorbets, Granitas, and Sweet Accompaniments by David Lebovitz. The key to this ice cream is lots of egg yolks that make for a stunningly rich texture whether frozen in a conventional ice cream maker or with liquid nitrogen.
What you need
1 cup half-and-half cream
3/4 cup sugar
Pinch of salt
2 cups heavy cream
1/4 teaspoon vanilla extract
2/3 cup malt powder
6 large egg yolks
2 cups malted-milk balls, coarsely chopped
What you do
Warm the half-and-half, sugar and salt in a medium saucepan. In a large bowl, whisk together the heavy cream, vanilla and malt powder, and set a mesh strainer on top.
In a separate medium bowl, whisk together the egg yolks. Slowly pour the warm mixture into the egg yolks, whisking constantly, then scrape the warmed egg yolks back into the saucepan.
Stir the mixture constantly over medium heat with a heatproof spatula, scraping the bottom as you stir, until the mixture thickens and coats the spatula.
Pour this custard through the strainer and whisk it into the malted-milk mixture. Stir over an ice bath until cool.
Chill the mixture thoroughly in the refrigerator.
To churn conventionally: Freeze the mixture in your ice cream maker according to the manufacturer's instructions. As you remove the ice cream from the machine, fold in the chopped malted-milk balls.
To churn with liquid nitrogen: When handling liquid nitrogen, wear suitable gear, including a long-sleeved shirt, pants, socks, shoes, safety gloves and goggles. If indoors, use only in a large, well-ventilated space near open windows or doors.
Fill a metal or wooden bowl, or styrofoam container, with about 4 cups of liquid nitrogen and set aside.
If using a stand mixer, use the paddle attachment. Add the mixture and turn the mixer on to its lowest setting.
Slowly add the liquid nitrogen to the mixture, in small amounts, scraping down the sides of the bowl, if necessary, until the mixture is slightly firmer than the consistency of soft-serve ice cream.
If using a wooden spoon, add the mixture to a large, deep, metal or wooden bowl. Slowly add the liquid nitrogen in small amounts, stirring constantly until the mixture is slightly firmer than the consistency of soft-serve ice cream.
Fold in the chopped malted-milk balls and serve immediately. Freeze leftovers in an airtight container.
Adapted recipe reprinted with permission from The Perfect Scoop: Ice Creams, Sorbets, Granitas, and Sweet Accompaniments by David Lebovitz, copyright © 2007. Published by Ten Speed Press (www.tenspeed.com).
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