Nitrogen cavitation is a technique that allows for one to rapidly infuse flavors into alcohol in minutes, rather than days. All it takes is a cream whipper. The technique made its way around the internet in 2010 when Dave Arnold posted about it. His theory was that the pressure forces the alcohol into the pores of whatever’s being used for flavoring, and the release of pressure causes cavitation and agitation as the bubbles of nitrogen are released. This technique is used in biology labs to rapidly break cell walls, so there is likely some truth to this theory.
My lovely partner got me an iSi Cream Whipper for Christmas, and of course I needed to give this a shot immediately. A coworker had brought in some DIY coffee liquor not long ago for me to try, and it was delicious. The recipe he used involved cold brewing the coffee, then adding rum, simple syrup, and a vanilla bean, and letting that steep for 3 days, and the end result is a delicious, 20% ABV coffee liquor along the lines of Kahlua. I figured this would be a good test for nitrogen cavitation infusion, since it would let me infuse the coffee and vanilla bean flavors directly into the rum, avoiding watering it down with coffee; would reduce the time it takes to make from 4+ days down to minutes; and would produce a higher ABV product, since it wouldn’t be watered down with the water from the coffee.
As far as technique, since the Dave Arnold article doesn’t explicitly list one, I went with one from Kaiser Penguin for 5-minute falernum, which is where I first heard of this technique. I had already poured 16oz of rum into the whipper when I re-read it and noticed that it says that 8oz produces a better result, so I went through with it anyway and it still turned out great.
- 2 cups overproof rum (Wray & Nephew)
- 1/4 cup coffee (cold brew grind, 20 on a Baratza Encore; espresso is called for in the Serious Eats recipe, but I used JUST Coffee Company’s Wake the Dead)
- 1 vanilla bean (split, scraped, bean retained)
- 1 cup demerara simple syrup (equal parts demerara sugar and water boiled)
- Add rum, coffee grounds, and vanilla bean scrapings and bean halves to the body of the whipper.
- Attach whipper top and add 1 canister of nitrogen.
- Swirl the whipper gently for 1 minute.
- Let the whipper sit for 30 second.
- With a glass over the whipper nozzle, release pressure from the whipper. If liquid comes out of the nozzle, reduce release rate. Continue this until all hissing stops and all pressure is released from the whipper.
- Remove top of whipper.
- Pour whipper contents through a cheesecloth-lined strainer into a measuring cup at least 2c in storage volume.
- Let mixture sit for five minutes.
- Pour the contents of the measuring cup into a storage vessel, leaving behind fines.
- Add demerara simple syrup to storage vessel.
- Seal storage vessel and swirl to combine.
Based on my yield (1.75c of liquid after straining and removing fines) and the proof of the Wray & Nephew (63%), adding the cup of simple syrup took it to ~40%, which was the goal. The end result still has the hogo I expect from Wray & Nephew, but a smooth coffee taste that coats the tongue, a slightly thicker mouthfeel than straight rum, and a lovely roundness to the taste from the vanilla. While I may have ended up with a more pronounced coffee flavor from using only 8oz of rum, according to Kaiser Penguin and Dave Arnold, I’m quite happy with the flavors that came through. The aroma is also very coffee-forward, which I like.
I’m going to continue to experiment with this technique and how it can be used to produce various infused liquors. At the very least, I plan to try that 5-minute falernum recipe and compare it to the velvet falernum I’ve been using.