Why is liquid nitrogen (LN2) ice cream "creamier" than regular ice cream?
The secret to creamy ice cream is the rapid freezing of the fat and water particles. The faster the ice cream can be frozen, the fewer ice crystals that can form, the creamier the concoction.
Liquid Nitrogen boils at −321 °F. Which means, holy guacamole that is cold! You'll be want to careful not to expose your skin to it or hold your hand in it, unless you're trying to lose a limb. A drop on the arm isn't going to kill you, your body temperature will ensure that the LN2 rapidly boils off, but it will feel very cold.
Here's what you need to safely make LN2 Ice Cream:
One dewar (a super insulated flask designed to hold LN2). I do not recommend using a regular store bought thermos. It may hold the LN2, but will rapidly degrade and fall apart, frozen apart by the extremely cold temperature within. Dewars are expensive, so if you have a friend at a chemistry lab, check there first.
Gloves -- you can try oven mitts or household cleaning gloves that go up your arm
A strong wooden spoon -- a metal spoon will conduct the cold and make it really uncomfortable to mix your liquid nitrogen ice cream. Go with wood.
A giant bowl
Liquid Nitrogen -- the best part. This can be purchased on site at Air Gas or similar industrial gas outlets. Expect it to cost anywhere from $3 - $8 a liter.
Your delicious ice cream recipe (mixed together, but not frozen)
Got all that? Good! We're ready to make Liquid Nitrogen Ice Cream!
Step 1: Making Liquid Nitrogen Ice Cream: Technique
If all that sounds too fancy for your taste, you can also just eyeball cream, sugar, vanilla and your favorite condiments into your mixing bowl and freeze that with LN2. But, IMHO, fancy pants ice cream custards are the way to go.
So, you've got your base, ready to be frozen. Here's the deal. You're going to need roughly 1L of LN2 for every litre of ice cream base. If you're like me and bought 30L of LN2 this would be way to dangerous to pour from a 30L dewar. In which case, you should move part of your 30L LN2 into a smaller, lighter, more manageable, container that you can use to pour directly into the bowl.
Did I mention this is a two woman job? That's right. If you're making LN2 ice cream, you should be making it with friends because it's a TOTAL spectacle to behold. So grab a friend seems thrilled by working with dangerous materials, as opposed to being scared by them, and you're golden.
Here we go:
1. Pour your custard ice cream base into your big bowl. Put on your gloves (the both of you) and get your wooden spoon ready.
2. With your LN2 in a smaller dewar, SLOWLY pour the LN2 into the custard mixture. Stir gently. Blow on the smoke so you can see what you're mixing (and wow the audience that has grown around the table at the sight of smoke everywhere).
3. Pace is the key. Continue to slowly pour LN2 into the custard mixture at a slow, measured pace. Continue stirring. Eventually you will feel the mixture coming together. At this point, stir more vigorously.
4. Suddenly it will be come a heck of a lot harder to stir. You're almost there. Stir for you LIFE! Scrape down the sides which are no doubt frozen to the bowl and whip that up!
5. Check out what's in your bowl. It's ice cream! Grab cones, spoons, bowls ... whatever it takes, and eat it up.
6. Repeat with another type of ice cream base.
7. Gain major nerd cred.