Liquid Nitrogen: Part 4

Normally in April I would be on vacation bicycling in sunny Mallorca Spain for two weeks.  Alas, both last year and this, the Covid pandemic has kept us all at home.  I have used this time to explore new areas of interest, and dare I say like many, cocktailing!  How I came to be interested in mixology is a story in itself and which is probably better shared over a cocktail rather than a blog post. But for now, in keeping with the theme of liquid nitrogen, I will share my latest experiment with both, and in particular LN2 glass chilling.

In case you haven’t read Liquid Nitrogen: Part 1, Liquid Nitrogen (LN2) is the liquid form of Nitrogen which while normally a gas, in its liquid state is extremely cold, −195.79°C. This property allows for some very interesting uses in modernist cuisine including Cryofrying, Cryo-grinding , and Cryo-shattering.

While researching the fascinating world of cocktails, I came across a superb book titled “Liquid Intelligence: the art and science of the perfect cocktail”.  Written by Dave Arnold in 2014, it was winner of the 2015 James Beard Award for Best Beverage Book and the 2015 IACP Jane Grigson Award. For those not familiar with Dave Arnold, he is a food science writer and innovator.  He hosts the radio show Cooking Issues, ran the cocktail bar Booker & Dax (once part of the Momofuku restaurant group but now closed) in New York City, and has taught at the French Culinary Institute and Harvard University.  The book explores temperature, carbonation, clarification, and sugar concentrations amongst other things.  His chapters on temperature and alternate chilling led me to experiment with LN2 and cocktails, and in particular chilling glasses.

It’s important to emphasize that while working with LN2 does pose some risks, it can be safely handled if one takes some basic precautions, including not to ingest it!  While that would seem obvious, there was a very unfortunate incident in which a young women suffered extensive damage to her esophagus and stomach from inadvertently drinking LN2 served in her cocktail at a bar in England. I speculate the bartender probably used LN2 to create fog for the theatrical effect more than to cool the drink, as LN2 although extremely cold is somewhat counterintuitively a poor method to chill a cocktail for several reasons.

Compared to water and ice, LN2 has both a low latent heat of vaporization and low specific heat: a gram of LN2 only has the same chilling power as 1.15g of ice. LN2 is also inefficient because it boils off until it has sufficiently cooled the cocktail. And because it is not as dense as water or alcohol, it floats on the surface requiring vigorous stirring to cool the entire drink. This creates a fog as it boils off so it is hard to see what you are doing increasing the risk of splashing the drink. (There is a technique Dave Arnold develop which he calls the “Rock and Roll” which allows one to safely chill a drink using LN2, but he only recommends this for some very particular applications.)

So what use is there for LN2 in cocktailing?  It turns out it is terrific for chilling glasses.  Cocktails should always be served in a chilled glass so the drink which one has so attentively shaken or stirred to cool and mix, doesn’t warm prematurely.  I believe it was Dave Arnold who said, a warm cocktail is a sad cocktail!  Traditionally ones glass is chilled by either adding ice and water to the glass and then emptying before serving the drink, or placing the glasses in a chiller / freezer.  Water and ice while effective leaves some water in the glass and putting glasses in a freezer takes up space. Further, as Frederic Yarm has demonstrated, both take several minutes to chill a glass.

Dave Arnold described a technique done “À la Minute” using LN2 which is fast, effective, and leaves the glass dry.  Aside from the advantage of glasses not taking up space in a chiller, it also allows one to chill just the bowl of the glass sparing the rim and stem making it nicer to hold and drink from. And, it adds a little theatre!  The technique is simple. You will need a thermos with some LN2 from which you pour a little LN2 into a glass and swirl it for a few seconds.  Most importantly, you then pour the LN2 back into the thermos; you must never serve a cocktail with residual LN2 in it.

You might be asking doesn’t the thermal shock from such rapid cooling shatter the glass?  It turns out that with the appropriate glass this isn’t an issue.  In developing this technique, he found that the quality i.e. expense of the glass, had no bearing on breakage.  Glasses that are uniformly thick, have flat bottoms or corners, or have thins walls and a thick base tend to crack.  He suggests testing two or three of the same glass because he found that if none break, then you will be safe in using that make / style going forward.  He does caution against using glasses that don’t curve in at the lip as when swirling, you otherwise risk the LN2 splashing over the edge.  Champagne flutes, wineglasses, and coupes are suitable, a martini glass not so much! Lastly, glasses should be dry.

This video demonstrates his technique nicely:

I have tried this a few times now with my standard cocktail coupe which I bought from Cocktail Kingdom without breakage. It is a sturdy, inexpensive, and most importantly dishwasher proof glass!  The only thing I’m not keen on is that it has a beaded rim, but maybe that’s just a wine snob thing!

Here is my first attempt at this technique.

Chilling glass with LN2

Having chilled the glass with LN2, I wanted to compare it with one traditionally chilled in the freezer. The image below shows them side by side.

Glass on the left chilled with LN2 and glass on right chilled in freezer

The most obvious difference is that the LN2 glass stem did not frost up because only the bowl was chilled while the freezer chilled glass completely frosted. Because I was taking photos, the LN2 was in the glass longer than just a few seconds so you can see the top of the stem is just started to cool and frost up and the lip which I hoped not to chill, in fact did. You can also just make out a LN2 fog spilling over and down the glass because LN2 is denser than air (but less dense than water or alcohol so it floats).

For the test, I made a Gennaros Sidecar a riff on the classic Sidecar made with the addition of Limoncello.

Finished cocktail!

The drink was delicious. However, having left the LN2 in the glass too long resulted in over-chilling the bottom of the bowl with consequences as shown below in the next two photos. The first issue was that the bottom was so cold it froze the drink into a slush.

Note the frozen slushy at the bottom of glass

The second issue was that ice accumulated on the outside of the glass.

Note the ice that formed on the side of glass

I didn’t find either of these an issue, indeed, both resulted in a longer lasting cold drink. But the whole point of LN2 chilling is to have a perfectly chilled glass, without chilling the rim or lip. Having learned from my first attempt, I can report subsequent drinks have been perfect.

So aside from the need to source LN2 and its expense, is it worth the effort? Short answer is not for the casual home mixologist, especially if you don’t have other uses for LN2. And if you as I have space in the freezer to always keep a couple of glasses pre-chilled, no need to keep LN2 on hand just for this.  However, as there are so many other uses for LN2 about which I will post, I usually have some on hand for special occasions, so why not also chill a few glasses!