By Tom Nordin
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| Photo: Making LN2 ice cream is always a
really big hit. |
We have made the "world's most expensive ice cream" for
Keck Observatory on several occasions. Because the LN2 is
so cold (-320 °F), it freezes on contact with the mixture,
resulting in microscopic ice crystals. This is why LN2 ice
cream is so very creamy (well, the half-n-half helps too…).
I first learned of this gastronomic treat in preparation
for the Keck Observatory Open House. We use LN2 and Liquid
Helium (LHe, -452 °F) at the observatory to lower the electrical
noise on our cameras, and we wanted to demonstrate this
technology to the public. We researched what others had
done to demonstrate the properties of LN2, and we found
some really interesting displays, including:
- Freezing flowers and seeing how fragile they are when
frozen;
- Freezing a Penny and watching it shatter when hit with a hammer;
- Freezing inflated balloons and watching them contract to a thin wafer - as if there was no gas in them at all - then holding them in your hand and having them reinflate on their own;
- Pounding nails with frozen bananas;
- Whistling tea kettle, filled with LN2, just sitting on a tabletop; and best of all
- Liquid Nitrogen Ice Cream!
We have added some really unique things to the LN2 ice cream over the years. We freeze mini-marshmallows and they turn out crispy, kind of like the marshmallows in Lucky Charms. Kids love this. Personally, I think the best LN2 ice cream we have made was with steaming hot Kona coffee. One steaming cup of Kona coffee added to the mix (without the vanilla) produced a super tasting Kona coffee ice cream. The coffee bean experiment was not as successful, costing me a broken tooth!
The recipe for LN2 Ice Cream is:
- 2 Cups Half-n-Half
- ¾ Cup Sugar
- 1 Tablespoon Real Vanilla Extract
- 1 Quart LN2
Directions:
Mix the first three ingredients together.
While stirring the mixture, slowly add the LN2, while counting back from 60.
When you get to zero - you have ice cream! 
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