Cryo-gem: liquid nitrogen ice cream and marshmallows Alaska
My most memorable experience with liquid nitrogen is not the first time I watched someone cook with it at Moto, nor is it the first time I used it to turn orange juice into sorbet; it's not even the first time I tasted my first batch of liquid nitrogen ice cream.
No, those are memorable, but not that memorable. That honour goes undoubtedly to the ride home after my second fill up when, after driving less than a block with a freshly filled ten litre dewar, we hit a bump. The force of the impact briefly lifted the lid off the dewar, sending a few tiny streams of liquid nitrogen skyward. None of this is too particularly troubling unless, of course, the dewar just happens to be nestled between your legs while streams of unbelievably cold liquid nitrogen arc towards your crotch.
Unfortunately, that was precisely my situation.
In its liquid form, nitrogen reaches mind- (and body-) numbingly cold temperatures around -196C. That's frigid enough to do horrific damage. A minuscule amount in the eye can blind, and sufficient amounts elsewhere cause frostbite and 'burns' equivalent to hot frying fat. This is nasty stuff.
So during that brief flicker of time between the liquid nitrogen escaping the dewar and it landing on the fabric covering my boys (I have a strict policy about never transporting liquid nitrogen while naked), two thoughts went through my mind: How much is this gonna hurt? and Will Rachel still love me if I were a eunuch?
Thank God we didn't have to find out.
The corollary to nitrogen being a liquid below -196C is that it turns into a gas -- that is it literally boils -- above it, so you can imagine what happened on this particular hot summer day. Drops of liquid nitrogen splashed on my crotch and the seat beneath it, and those that hadn't evaporated during the flight to my nether regions promptly did so with a sizzle on my crotch (sadly, I can take no credit for my sizzling manhood. This time.).
The whole episode took no more than a few seconds, if that, but it highlights just how volatile and dangerous liquid nitrogen can be.
Liquid nitrogen's incredibly low temperature make it dangerous, but it also makes it the ultimate medium for preparing ice cream. That's because the texture of ice cream -- its creaminess and smoothness -- are directly related to how quickly it's frozen. Longer freezing times encourage ice crystal growth, crystals that feel gritty on the tongue, which, at least in my opinion, doesn't make for enjoyable ice cream.
I didn't want to have to resort to using liquid nitrogen -- well, okay, the geek in me absolutely did -- but I was driven to it by conventional ice cream makers like my Cuisinart standby. It hurts to bash it, because my in-laws gave it to me and because it's helped me make a lot of really great ice cream, but it's just not in the same league.
To prove it, I invited some friends over for a semi-blind taste test. The best test was a Philadelphia-style vanilla ice cream showdown for which I made a double batch of base frozen three ways: in my Cuisinart, in my friend's KitchenAid ice cream maker attachment, and with the paddle attachment of my KitchenAid stand mixer using liquid nitrogen. I also added vanilla bean Haagen-Dazs and a cup of vanilla gelato from my local gelateria for good measure.
My friend's knew the five kinds of ice cream I'd be serving them, but they didn't know which was which. They all agreed that the gelato was the worst of the five, not simply based on its overly sweet and largely non-existent vanilla taste, but also because of its weak, overly light texture. I have no doubt this is because it had far more air beaten into it than any other ice cream in the tasting.
The Haagen-Dazs fared better but didn't stack up to the homemade versions. Even the Cuisinart version, which ranked dead last among homemade ice creams, garnered more votes. All three homemade ice creams shared a wonderful taste -- when it comes to ice creams, homemade equals unparalleled flavour regardless of how it's frozen -- but the Cuisinart ice cream had a noticeably icy texture.
The KitchenAid ice cream, on the hand, was excellent with almost no crystallization. In fact, my only real complaint about it is that it left a thin film of greasy fat, likely butter, in the bowl of the attachment after churning. That said, it produced ice cream so good that a couple of people made it their first choice, even over the ice cream prepared in liquid nitrogen.
The majority of the tasters still chose liquid nitrogen ice cream, and it finished no worse than second on anyone's ballot. The fine line between those who preferred the KitchenAid over the liquid nitrogen seems to be that some of the tasters found the liquid nitrogen ice cream almost too dense and heavy.
That's precisely what I love about it. Liquid nitrogen ice cream has a dense, custard-like mouthfeel; it's sort of what I imagine pudding would taste like were it frozen, and the effect is amplified when preparing egg-based (aka French-style) ice creams.
I say this from a position of experience. The past two months have been a liquid nitrogen-induced fog of frozen goodness. In addition to dairy-based vanilla, I've also made similar strawberry, chocolate, and chocolate and Guinness ice creams. The list of egg-based ice creams I've made is even longer: panforte with strands of candied citrus peel that takes me back to our honeymoon in Siena; coffee, which makes for one helluva breakfast; toasted almond and cherry that sends Rachel over the moon with delight; and malted, my personal favourite, especially when I bite into a large spoonful with a crunchy Malteser, the best malted balls in creation.
Fellow ice cream aficionados may recognize that a number of the ice creams I mentioned come directly from David Lebovitz's book, The Perfect Scoop. I've come to love that book over the past few months, and it's now my ice cream bible. The fact that a book written by a former member of the Chez Panisse pastry kitchen is now my starting point when looking for recipes to freeze with liquid nitrogen is an irony that amuses me considerably.
Liquid nitrogen need not be used solely to make conventional ice cream. As I wrote earlier, my first experiment with liquid nitrogen included plain orange juice, which becomes a refreshing, if slightly watery, sorbet. To really take advantage of liquid nitrogen's freezing power, however, turn to the liquor cabinet.
Pure ethanol -- the happy juice in alcoholic drinks -- freezes at -114C. Only those with a death wish drink pure ethanol, however, so we only have to worry about temperatures closer to 0C since the booze we consume is, literally, watered down to prevent an ugly death. That said, 100 proof alcohol still requires temperatures of -32C to freeze, and no home ice cream maker can approach that.
It's child's play for liquid nitrogen, however. Watermelon-infused vodka, for example, freezes into a refreshing sorbet that packs a huge wallop. Bailey's turns into something magical. Frozen, its texture is identical to incredibly smooth ice cream and it tastes delicious. This is something of a problem given that eating a small scoop of Bailey's ice cream is the equivalent of drinking three or fours shots of liquor in just a couple of minutes. Let's just say the Bailey's ice cream is the last frozen treat one makes during a session of liquid nitrogen experimentation.
There are uses beyond ice cream for liquid nitrogen. I've not yet had a chance to experiment with some of the recipes from el Bulli, though I will soon, but even our less haute experiments produced intriguing results. We 'cooked' Cheezies in liquid nitrogen and discovered that biting into one produces a rush of air that feels something like blowing into a balloon then releasing the air in it directly into the mouth. The force was sometimes powerful enough to actually force our mouths open.
My favourite alternative preparation came from Rachel while we were experimenting with some friends. Upon trying a frozen marshmallow, she suggested freezing one then scorching one end of it using our brulee torch. It's the avant-garde version of baked Alaska and it's awesome because it produces a simple sugary treat with several distinct textures and flavours. The frozen end has a crispy exterior and a soft, chewy interior, while the bruleed side has that slightly oozy melted sugar texture along with a complex burnt sugar taste. For a dish so simple in its conception and execution, I love how complex 'marshmallows Alaska' tastes and feels. It's an experience I won't soon forget.
The key word is 'soon,' of course. 'Never' is a word I now reserve for an entirely different order of liquid nitrogen experiences.