DocBug

Liquid-Nitrogen Ice Cream

Last weekend I threw a house-cooling party, and I figure what can be better to cool a house than liquid-nitrogen ice-cream? I made up a big batch of unflavored ice-cream base, got some lN2 and had people bring whatever flavorings they wanted to try mixing into a micro-batch of ice cream. Having learned from my mistakes the last two times I've made it, this stuff was some of the creamiest, best ice cream I've had.

A few lessons learned:

• Whenever the recipe calls for milk, half-and-half or cream, use whipping cream. Depending on how hard you mix it, this'll make soft ice cream anywhere from creamy to frozen-mousse.
• It's really hard to hand-stir quickly enough to keep hard chunks from forming (and besides, hand-stirring is so last-century). I expect egg-beaters would work, but I really like the results we got with my cordless drill and the the quart-capacity McMaster coil-spring mixing attachment (part #35325K51, halfway down the page). If it's worth doing, it's worth doing with power tools.
• Liquid nitrogen is deceptively safe-looking, at least unless something goes wrong. Safety goggles are a must, and long gloves are recommended. It's fairly safe if it splashes on your skin because you're protected by an insulating layer of nitrogen vapor, but don't let it pool against your skin (duh) or super-cool metal or other material that then touches skin. Also be sure you've got good ventilation.
• Wasabi & Mexican mole ice-cream is better than it sounds, but still not good. Balsamic vinegar & olive-oil ice-cream is nasty on its own, but is OK on crackers.

The winning flavor of the night, by my taste at least, was the orange-raspberry sorbet. In the interests of posterity (and so I can find it when I want it next time), here's the recipe:

Ingredients:

• 1 cup baker's sugar (aka fine granulated sugar)
• 3/4 pint water
• zest of 2 oranges
• 1/2 pint fresh-squeezed orange juice
• juice from a whole lemon
• 3/4 cup raspberry lambic
• about 2 pints liquid nitrogen¹

Mix sugar, water and orange zest together in a saucepan, stirring under low heat until the sugar has dissolved. Then bring to a boil and and let boil until you have a syrup — roughly 5 to 8 minutes. Remove from heat and let cool. When cool, stir in orange juice, lemon juice and raspberry lambic. This is your sorbet base. (You could put this in an ice-cream maker at this point, should you want to make it the old-fashioned way.)

Put base in a large bowl, and don safety glasses. If the bowl is metal, you'll probably want those gloves as well. Slowly pour liquid nitrogen into center of bowl, mixing all the while with electric mixer. (We use a tough plastic mug with a handle to pour the lN2 — don't use a metal cup.) Stop every few seconds to blow the fog away and to break up any solid ice-patches that have formed. Keep adding lN2 until sorbet is completely frozen. Sorbet will still be soft-serve, that's OK.

I hear that for best results you should put the sorbet (or ice cream) into the freezer for about 15 minutes to even out the ice crystals and "set," but I've never had the patience for that. Do make sure all the lN2 has boiled away though before putting any in your mouth, or else you might get a rude surprise.

Enjoy!

¹ Ask your local lab-supply store or physics grad student for food- or medical-grade liquid nitrogen, or follow these three easy steps to make your own! 1) Collect about 1000 pints of air for every 1 pint lN2 desired. 2) Chill air until nitrogen condenses (around -320 degrees Fahrenheit). 3) Skim off liquid nitrogen and keep in insulated container. Should any liquid oxygen sublimate, save for making flambé!

Posted by bug to at November 26, 2004 1:48 AM | TrackBack