Thanks to yet another missive from American Express – this one offering discounted prices on some cooking presentations at a place called Astor Center in New York City – we checked out what sort of culinary seminars Astor might be having during our visit in August. One particular course caught our attention – “Chilling Out With Liquid Nitrogen”, a presentation which promised to share a variety of uses of liquid nitrogen in the kitchen.
We first discovered the whole concept of using liquid nitrogen for “cooking” just a few months ago (May 2008), when we dined at The Fat Duck in England. Two of our courses were prepared with LN2 (as liquid nitrogen is called in technical circles).
After returning home we tried to find some affordable devices to generate LN2 for experimentation in our kitchen, but the cheapest system we found was over $11,000, and only available in the United States. Geography aside, that was well beyond our budget. And unlike in the U.S., no one on Bonaire makes LN2 for sale, so we’ve been unable to pursue our desires for experimentation with LN2 in the kitchen.
But, this class at Astor Center sounded like it might provide us with more insights, so we signed up, and were even given the courtesy of reserved seats so the kids could be in a location where they could be assured of a good view of the demo kitchen. Bas and Krystyana were the only kids present, and we surmise that a vast majority of the rest of the audience were “in the profession”, meaning they were chefs and restaurateurs. That was later confirmed for us when we discovered that Wiley Dufresne, the chef of New York’s top molecular gastronomy restaurant wd-50 had been sitting behind us during the presentation at Astor Center.
The presentation was conducted by newlywed chefs H. Alexander Talbot and Aki Kamozawa, who run a business called Ideas in Food. Alex and Aki also write a column for Popular Science about kitchen alchemy, including this article on playing with liquid nitrogen, a copy of which was given to us at the presentation.
A few facts of note about Nitrogen are important before I continue.
Nitrogen makes up about 75-78% of the air we breathe, with oxygen at around 21% and various other gases making up the difference. Nitrogen needs to be cooled down to around -196° C to become a liquid (it becomes solid at -210° C). Once liquid nitrogen hits -195.8° C, it boils, turning back to gaseous form.
Working with liquid nitrogen is not particularly safe, as it can splash or splatter on your skin and cause “burns”, and likewise, if used in conductive containers you can suffer burns or even more embarrassing side effects from touching such containers, especially with damp body part (flash to the tongue stuck to the frozen metal pole in the movie “Christmas Story”). Liquid nitrogen is also commonly used by dermatologists to try and freeze off warts, as I can testify to from personal experience.
Also, as LN2 becomes a gas, if there’s not even ventilation you could potentially asphyxiate, or at least suffer from dizziness or nausea, if not a loss of consciousness. On a related note, in a recent episode of Burn Notice, nitrogen gas was used to assassinate someone by causing them to asphyxiate.
But, if you can overcome these varied dangers LN2 can be pretty fun to play with, as we witnessed in the presentation by Aki and Alex.
To whit, LN2 has been used for some time to make ice cream because it freezes fats and sugars so quickly you don’t have to spend lengthy periods churning the cream to break up the ice crystals that would otherwise form in traditional ice cream making. However, at the same time, you actually have to temper the produced ice cream to ensure it’s not so cold as to cause burns. Aki and Alex suggested that in order for items which have been thoroughly frozen with LN2 to be edible you should temper the items in a regular freezer to warm them up. Weird concept – thawing something in a freezer.
Alex and Aki also recommend using LN2 for several particular kitchen functions other than making ice cream. One of those is to create finely ground or even powdered versions of pretty much any ingredient. During the presentation at Astor Center, they deep froze and then powdered (using a Vita-Mix commercial kitchen blender) the following ingredients (many of which we got to sample in one form or another):
- Raw shrimp
- Chorizo sausage
- Black olives
- Raisins (normal)
- Sultanas (blond raisins)
Using traditional methods, none of the above items could be turned into a powder. Instead you’d end up with either a greasy or sticky-sweet mush at best. But the low temperature of LN2 causes even fat to become a hard solid that can then be easily (with the right equipment) broken and shattered into a powder.
When raw ingredients like shrimp are used, the idea is that you’d use the resulting powder to flavor a dish you will later be cooking. This was demonstrated with an extremely creamy grits Alex had made using cyro-vac sealing and a pressure cooker. After the grits was finished it was then put in a pot with the shrimp powder and the two blended together by hand over heat, resulting in shrimp-flavored grits. (And then served to us over a bed of powdered chorizo and pepperoni – delightful!)
A side effect of cooking with LN2 is that it will also dehydrate things put into it. Visually this results in clouds of vapor as the nitrogen boils off and takes water with it. Aki explain that when “cooking” with LN2, one way she knows that things are thoroughly frozen is when the LN2 stops bubbling and crackling, much in the same way oil stops sizzling loudly when it has cooked away the water in an item placed in it. This dehydration also aids in the powdering of food items frozen with LN2.
Alex also told us that he has found that using LN2 to freeze vegetables both retains and even concentrates the flavor of the vegetables, while at the same time tenderizing them and more cool yet, allowing one to shatter the vegetables to produce dramatic presentation when the vegetables are incorporated into a dish.
With things like nuts, you can make natural butters with all the flavor of the nut and no additional ingredients when you first freeze the nuts with LN2 and then grind the frozen nuts.
And, LN2 is so cold that you can even freeze alcohol into a solid, although it’s then too cold to consume without being tempered, which might cause it to melt. But a neat concept nonetheless.
In big cities like New York, LN2 can be had for about $2/liter. You need to get a dewar (eBay) – basically a giant ultra-thermos which costs many hundreds of dollars and then determine if you want a nozzle to pump the LN2 out, or if you’re comfortable simply pouring the LN2 into the vessel(s) you plan to “cook” in. Alex and Aki used Styrofoam coolers for their demonstration. It should be noted that while LN2 does boil at a low temperature, this boiling effect is more of an issue when in contact with warm solids than with air, although the cooler the air in the work area where the LN2 is being used, the longer the LN2 will survive before boiling off completely. That could be another reason that LN2 might not work so well for us on Bonaire, where the average temperature is around 85 degrees Fahrenheit year round.
The class lasted almost two hours, during which time, in addition to all the information I have noted above, Alex and Aki created a popcorn gelato, a frozen yuzu cloud used to chill a smoky mescal, creamy shrimp-flavored grits on a bed of powdered sausage, pureed almonds, frozen shattered carrots and beets, and a taste-packed rum raisin ice cream covered in powdered sultanas. And all prepared with liquid nitrogen.
While we learned a lot about the practical application of liquid nitrogen in the kitchen, we left yearning for a way we could experiment with LN2 ourselves back home in our kitchen on Bonaire. Sadly, that’s just not viable at this time (although Alex suggested we could try with dry ice), but we may well see about borrowing some friend’s kitchen in big cities in the U.S. when we come to visit, and having a dewar shipped to them in advance of our visit.
In closing I should add that the Astor Center’s classroom is quite well set-up, with two levels of seating arranged so that pretty much everyone has a good view of what the presenter is working on, with video cameras and flat screen displays to show more detail when needed. We’ll definitely be checking their schedule again when we next visit New York City.
More details on cooking with liquid nitrogen, as well as some recipes can be found in Alex and Aki’s article.
Click on the above pictures to enlarge them and get captions. You can also see all photos taken during this presentation on Flickr.