by Jeff Potter
Note
Standard lab safety protocols for driving small quantities of liquid nitrogen around usually state that two people should be in the car and that you should drive with the windows down or at least cracked.
When it comes to working with liquid nitrogen, I find it easiest to work with a small quantity in a metal bowl placed on top of wooden cutting board. Keep your eyes on the container, and avoid placing yourself in a situation where, if the container were to fail, you would find yourself getting splashed.
Don’t sit at a table while working with it. Standing is probably a good general rule to reduce chances of injury. And remember: it’s cold! Placing a noninsulated container such as a metal bowl directly on top of countertops, especially glass ones, is not a good idea.
Note
I once cracked a very nice countertop with an empty but still cold bowl during a demo at a large software company whose name begins with the letter M. I’m still sheepishly apologizing for it.
One final tip: when serving guests something straightaway after contact with liquid nitrogen, check the temperature (using an IR thermometer) to make sure the food is warm enough. (As a guideline, standard consumer freezers run around –10°F / –23°C.)
Making dusts
One of the classic "silly things you can do with liquid nitrogen" tricks is to freeze a leaf or a rose and then whack it against something to shatter it. Unlike traditional methods of freezing, liquid nitrogen freezes the water in the plant so quickly that the ice crystals do not have time to aggregate into crystals large enough to pierce the cell walls and destroy the tissue, meaning the leaf or flower won’t wilt when thawed.
In culinary applications, you can use this same property to create "dust" from plant material. Lavender flowers, for example, can be rapidly frozen, crushed with a mortar and pestle (which needs to be chilled in a freezer to keep the frozen plant material from thawing), and then allowed to thaw back out. Some chefs have frozen larger items—beets, for example—causing them to shatter in an organic pattern that couldn’t be obtained with a knife.
Making ice cream
The standard formula for LN2 ice cream goes something like this: cream + flavoring + liquid nitrogen + whisking / mixing = 30-second ice cream.
While you can make ice cream with a small quantity of alcohol using traditional methods, those versions have only a mild flavor brought by the alcohols, which are used more as extracts or flavorings than as actual components of the body. With liquid nitrogen, however, you can make a scoop of ice cream with an entire shot of alcohol. Calories are no longer the biggest problem with this type of ice cream; hangovers are.
As with anything you make with liquid nitrogen that’s served cold, check to make sure that it’s not too cold before serving it. An IR thermometer is a handy tool for this. Spot-check your ice cream, and if it’s too cold, let it warm up to normal freezer temperature.
Cocoa-Goldschläger Ice Cream
In the metal bowl of a stand mixer, mix:
1 cup (256g) milk
1 cup (240g) heavy cream
¾ cup (180g) Goldschläger (cinnamon liqueur)
¼ cup (80g) chocolate syrup
½ cup (80g) bittersweet chocolate, melted
2 tablespoons (25g) sugar
½ teaspoon (1g) salt
½ teaspoon (1g) cinnamon
Taste the mixture to check the balance (try not to drink it all at this point), and adjust accordingly. Once frozen, the mixture will not taste as strong, so an overly strong mixture is desirable.
Turn your stand mixer on and (carefully! with goggles and gloves!) slowly pour in liquid nitrogen. I find it takes about a 1:1 ratio of mixture to liquid nitrogen to set the ice cream. If you don’t have a stand mixer, you can also do this in a metal bowl and stir with a whisk or wooden spoon.
Note
To melt the chocolate, microwave the milk and then add the chocolate to the hot milk. Let it rest for a minute, so the chocolate warms up, and then mix to combine. You can nuke the chocolate directly as well, but I find it easier and less likely to burn doing it this way.
Playing with Dry Ice
Dry ice—solid carbon dioxide—is easier to work with than liquid nitrogen. For one thing, it’s solid, so you don’t need specialized equipment to handle it. A Styrofoam cooler or even a cardboard box is sufficient. And secondly, it’s much more readily available. Just make sure to ask for food-grade dry ice!
A few words of warning: like liquid nitrogen, dry ice expands into a much larger volume as it sublimates. Do not store dry ice in a sealed container. Also, dry ice and ethanol form a wet slurry that is very dangerous. It’s not cold enough to generate the Leidenfrost effect, the phenomenon where a liquid generates a vapor barrier around a much-hotter item. Dry ice and ethanol can wick through clothing and stick to skin.
Besides sticking a chunk of dry ice in a cup of coffee and pretending not to notice while drinking from it (the chunk will sink to the bottom), what else can you do?
Quick-freeze berries. Industry lingo for this is IQF (individually quick frozen), in which large blast freezers rapidly freeze individual peas, raspberries, and chicken breasts. You can toss some dry ice in a Styrofoam cooler and mix in a roughly equal amount of berries or veggies, wait until the dry ice has sublimated away, and then bag ’em and stick them in the freezer.
Make ice cream. Works just like liquid nitrogen, only alcoholic flavors probably won’t set quite as nicely. Take your food-grade dry ice, place it between two towels, and give it a few whacks with something like a rubber mallet or the back of a frying pan to create a powder. Whisk the powder into the ice cream base until set.
Note
As with LN2 ice cream, it’ll take a little less dry ice if you start with a base already at freezing temperatures.
Create "fizzy fruit." Drop some grapes, bananas, strawberries—really, any moist fruit—into a pressure cooker, toss in some dry ice, and slap on the lid. As the dry ice sublimates, the chamber of the pressure cooker will hold the carbon dioxide (and bleed off any over-pressure amount), and the fruit will absorb some CO2. Wait 20 to 30 minutes, release the pressure, pop off the lid, and munch away.
DIY "Anti-Griddle" Using Dry Ice
If a griddle cooks foods by adding heat, it should follow that an anti-griddle "cooks" foods by removing heat. PolyScience, known by many chefs for its sous vide recirculating units, makes a product that does exactly that: its anti-griddle cools down whatever you put on the griddle surface.
You can make a do-it-yourself version by using dry ice, ethanol, and a sheet of stainless steel. You’ll need a solid chunk of stainless steel (plan on ordering a piece from a distributor such as McMaster-Carr). I have a 6″ × 6″ / 15 cm × 15 cm slab that normally lives in my freezer; it’s handy for those times when you want to cool down a small item quickly. Here’s how it works:
Rig up a bed of crushed dry ice. Try using a cookie sheet placed on top of a wooden cutting board. The cookie sheet will hold the dry ice/ethanol slurry, and the cutting board will provide insulation between the extremely cold cookie sheet and your countertop. Alternatively, if you have the lid to a Styrofoam container, using the inside, indented part can serve both purposes.
Pour a small amount of ethanol onto the bed of crushed dry ice—enough to create a level top. (You can use rubbing alcohol or cheap vodka.) The ethanol will remove any air gap between the pieces of dry ice and the stainless steel griddle, and it won’t cause the dry ice to froth in billowy clouds like water would.
Plop the square of stainless steel on top of the ethanol-topped dry ice. It should be a complete contact fit, just like a heat sink on top of a CPU.
Spray or coat the top surface of the stainless steel with a nonstick cooking spray, butter, or oil.
Drop your food to "cook" on the surface, smoothing it out into a pancake shape if desired. After 10 seconds or so, use a spatula to flip it and set the other side. As a starter, try whipping some cream up in a bowl with a bit of sugar and cho
colate syrup. Try using a cream whipper with flavored foams or the chocolate mousse recipe from earlier in this chapter.
Windell Oskay and Lenore Edman: Electrocuted Hot Dogs and Apple Pie
PHOTO OF WINDELL AND LENORE USED BY PERMISSION OF SCOTT BEALE, LAUGHING SQUID (HTTP://LAUGHINGSQUID.COM)
Windell Oskay and Lenore Edman blog about DIY and open source hardware projects on their website (http://www.evilmadscientist.com) and occasionally dive into the food arena with their "Play with your food" posts.
You are unique in the sense that you do some really extreme stuff both in hardware and in food. How much of what you do is happenstance versus planned?
Lenore: Most of the time we are brainstorming. Any topic is fair game for a project. We may have talked about doing an "Apple" apple pie long, long ago, and then we’re at the cooking store and looking at all of the different round-cornered square pans thinking, "This might work," or "Oh, wow! This is perfect!"
Windell: That also brings up one of the most important methods we have for solving problems, which is to put it on a list and wait for a really long time until we think of a solution.
How do you know if a project is going to work?
Lenore: You try it. The apple pie went through several iterations before we figured out a way to make it aesthetically pleasing.
Windell: There were a couple of different pie shells. We’re not running a commercial kitchen. It actually takes us time to make a pie shell and let it chill. We don’t have an extra one just sitting ready.
Why do you do these projects?
Lenore: That’s a good question. Why do you breathe?
Windell: What else are we supposed to be doing? We like to do cool stuff. We have a chance to, so why not?
Lenore: It’s rewarding to see other people enjoying our projects, so publishing them is rewarding. And you’ve got to eat, right? So you might as well eat something interesting. You have to wear clothes.
Windell: So wear something interesting.
If you knew the world were going to end tomorrow, what would you want your last meal to be?
Lenore: I don’t know... We eat a lot of good food, so it’s not like there’s one thing in particular that I would regret not having eaten.
Windell: If the world were going to end tomorrow, the last thing I think I would do is sit down and have a nice big comfy meal. It doesn’t really seem like that’s going to happen.
Lenore: I guess if you knew you couldn’t do anything about it, that might be a fine way to end. Sit down and have a big comfy meal. It seems unlikely, but...
Windell: Water and hard tack in the bunker.
Electrocuted Hot Dog
Since heat is a form of energy (heat = kinetic energy of molecules in a system), adding energy to a system can cause it to heat up, which is why a hot dog gets hot when electricity runs through it. (Hot dogs happen to be made of materials—proteins, fats, a little bit of salt—that are conductive enough for this to work.)
But the potential for killing yourself on a live wire is high enough that it’s not even funny to joke about doing it. If you really want to electrocute your dogs, search http://eBay.com for "Presto Hotdogger."
Visit http://www.evilmadscientist.com/article.php?story=hotdogs for more information.
P.S. LEDs light up when "plugged in" to a hot dog!
PHOTOS OF ELECTROCUTED HOT DOG USED BY PERMISSION OF WINDELL OSKAY
"Apple" Apple Pie
You too can make an Apple apple pie. Lenore and Windell used their laser cutter and a square springform pan, but with care, you can use a knife to cut the logo and a square glass pan to bake the pie. (If you’re not a purist shooting for an edible replica of a Mac Mini or Apple TV, a standard round pie will taste just as good.) For details, see http://www.evilmadscientist.com/article.php?story=ApplePie.
PHOTOS OF APPLE PIE USED BY PERMISSION OF LENORE EDMAN
Cooking with (a Lot of) Heat
Common and uncommon hot temperatures.
If cooking at 400°F / 200°C produces something yummy, surely cooking at 800°F / 425°C must produce something twice as yummy.
Well, okay, not quite—and by now, hopefully your mental model of how heat is transferred to food and the importance of time and temperature for gradients of doneness should have you slamming this book shut while muttering something about software engineers not understanding hardware. (Guilty as charged.)
But there are some edge cases—just as with "cooking" with cold—where extremely high heat can be used to achieve certain effects that are otherwise difficult. Let’s take a look at a few dishes that can be made by transferring lots of heat using blowtorches and high-temperature ovens.
Blowtorches for crème brûlée
Blowtorches can be used to provide very localized heat, enabling you to scorch and burn just those parts of the food at which you aim the flame. Torching tuna sushi, roasting peppers, and browning sous vide–cooked meats are all common uses, but creating the sugary crust on crème brûlée is the canonical excuse for a blowtorch in the kitchen. You can also use a blowtorch to prerender the fatty side of meats—try scoring and then torching the fatty side until it begins to brown before roasting.
When it comes to buying a torch, skip the "gourmet" torches and head to a hardware store to pick up a propane blowtorch—not a MAPP gas one, though. The smaller torches sold by kitchen specialty shops burn butane and work okay, but they don’t pack the same thermal punch as the hardware-store variety, which have larger nozzles and thus larger flames.
Quinn’s Crème Brûlée
Prepare six ramekins for baking by placing them in a large glass baking dish; set aside. Preheat oven to 325°F / 160°C.
In a bowl, separate out five large egg yolks, saving the egg whites for some other dish (see the section on egg whites in Mechanical Leaveners in Chapter 5 for suggestions). Whisk the egg yolks until light and frothy; set bowl aside.
In a saucepan, measure out:
2 cups (475g) heavy cream
½ cup (100g) sugar
Heavy cream and whipping cream are essentially the same thing in the United States. Heavy cream usually has a slightly higher percentage of fat while whipping cream typically has a stabilizer such as carrageenan added, but you can usually use either one regardless of what is called for.
Cut a vanilla bean lengthwise and use the edge of a spoon to scrape out the seeds. Add both seeds and bean to saucepan. Set the burner to medium heat and cook the cream, sugar, and vanilla for 10 minutes, stirring continuously. Meanwhile, in a separate pot, bring to a boil enough water to partially fill the glass baking dish holding the ramekins.
After the cream mixture has been cooked for 10 minutes, fetch out the vanilla bean and discard it. Strain the mixture through a ~400 micron filter (cheesecloth works fine) into a measuring cup or other container that’s easy to pour from.
Set the bowl with the egg yolks on the counter, where you can whisk the yolks with one hand and hold the saucepan with the other. Slowly drizzle the hot cream mixture into the egg yolks, whisking the entire time to prevent the hot cream from cooking the egg yolks. Too slow is okay; too fast, and you’ll end up with scrambled eggs. (Sweet, tasty scrambled eggs, to be sure.)
Ladle the mixture into the six ramekins, taking care to not transfer any foam that you may have whisked up. (The foam will float and set on top of the brûlée.) Add the boiling water into the baking dish—enough to reach halfway up the sides of the ramekins—and transfer to oven.
Bake until the centers of the custards jiggle just a little when shaken, about 30 to 35 minutes. They should reach an internal temperature of 180°F / 82°C. Remove ramekins from baking dish and chill in fridge until cold, about three hours. (You can store them longer, of course.)
You can create a quick work surface for blowtorching by flipping a cookie sheet upside down and setting the ramekins on top.
Once cold, sprinkle a thin coating of sugar over the top of the custard. Using a blowtorch, melt and caramelize the s
ugar, sweeping the flame slowly across the surface until you’re happy with the color and appearance. Keep in mind that darker sugar will be more bitter; also make sure to at least melt all of the sugar, as otherwise the granulated, unmelted sugar will give an odd mouth-feel.
Transfer ramekins to fridge and store for 10 minutes to allow the sugar to cool; then serve. You can hold the torched brûlée for up to an hour before the sugary crust begins to get soggy.
Note
Try infusing other flavors into the cream as you cook it, such as orange, coffee, cocoa powder, or tea.
You can "upgrade" Bananas Foster—a simple and tasty dessert where the bananas are cooked in butter and sugar, spiked with rum, and then served over vanilla ice cream—by sprinkling sugar on the cooked bananas and then using a blowtorch to caramelize the sugar. To create a work surface, flip a cast iron pan upside-down, line it with foil, and set the bananas on that.
Practice using a blowtorch by melting sugar sprinkled on a sheet of aluminum foil on top of a metal cookie sheet or cast iron pan. Don’t get the flame too close; this is the most common mistake when cooking with a blowtorch. The blue part of the flame is hottest, but the surrounding air beyond the tip will still be plenty hot. You’ll know you’re definitely too close when the aluminum foil begins to melt—around 1220°F / 660°C.
