The weird science of ethanol-water-sugar solutions - cooking some limoncello

I really wanted to do some house-crafted limoncello today, for our Italian restaurant. And instead of zesting lemons, I had the idea of using whole fruits.

Yes - usually zests working better - because there is far more surface. However my good friend, the sous-vide immersion circulator helped to cut the time in a fraction of traditional limoncello.

The normal procedure of limoncello is:

• Zest [cleaned] lemons
• Add them into alcohol
• Traditionally high proof grain alcohol is used - however using vodka is just fine, if you are regarding the difference in ABV.
• Obviously in Italy high proof booze is used, as it is in production far cheaper than the refined product 'vodka'.
• Wait for several weeks [depending on the size of the zest pieces].
• Strain and add sugar syrup [depending on the original occurring alcohol strength and the target strength].
• Bottle and label.

Now - I want to do this procedure as well - with two major differences:

• I want to use whole lemons - due to following reason
• I want to "hang" the lemons above the vodka - and don't want to suspend it into the liquor.

This is one procedure, I have seen in gizmodo.com. Not only it looks cool to use the whole fruits, it also results into a smoother result. And off course, every guest will ask "what you have there". Obviously things like that just increase the coolness of a venue.

The main problem is, that I need NOW limoncello.

There are several ways to fast-track infusions. You can cut the "botanical" into very small pieces - the more surface the faster the extraction [which is possible to practice in the extreme - pulverizing the botanical and then after infusing the liquor, filtering it out [or clarifying it].

Second: Nitro-cavitation. Add the botanical and the liquor into a siphon and charging it with N2O.

Honestly - this is not mine. I so wanted that it works - but the results of my tests weren't that great.

Third: Vacuum-cavitation. Yes - you can vacuum your liquor with the botanical inside - several times. You just have to make sure, that you don't pull a too strong vacuum and all alcohol boils over into your chamber vacuum sealer [which you definitely need for it].

Fourth: Use heat. The problem is, that if you would use your stove top, that over some time quite a lot of alcohol would evaporate. Less than ideal! Also - too high heat, would denature the flavors.

The solution is a immersion circulator [or any other "sous vide" equipment you do own].

As it is sealed in a plastic pouch, alcohol cannot evaporate - and the controlled temperature bath ensures, that it does not heat too much.

Now this is what I did:

• Wash lemons with ice water.
• Add them to a vacuum bag, add sugar and vodka.
• Seal the bag.
• Let them "swim" for about 3 hours at 55C.
• Refrigerate the pouch [as we are all children in hospitality we used the blast chiller... however an ice bath would be perfectly fine :) ]
• Open the bag, strain the lemons out of it.
• Add some water in the limoncello.
• Pour into a decorative bottle.
• Label...

It sounds a bit complicated, but really it isn't.

I used Sous Vide Supreme recipes - but found after tasting the limoncello, that they totally miscalculated the sugar - it needed some more. Also, the recipe is calling for far too much water - they mentioned a 1:1 ratio of vodka to water - and you would end up with about 20% abv [or lower], however proper limoncello has about 28-32% abv.

I roughly calculated that I needed to add about 300 ml of water to the mix [not about 1l!].

Now here was the weird thing, which lead to the unusual header: I added 1000 g water to 290 g sugar originally and added the lemons [which are quite solid]. After straining the liquid I ended up with 900 ml of vodka. What? Yes - angel share [or should I call it Poseidon share - cause everything stayed submerged in water?]. I tasted the lemons afterwards, but they were not saturated with alcohol. I can only think, that the sugar resulted in a far denser liquid?!? I don't even want to get too deep into it - as Chemistry wasn't my best discipline...

Anyway - all resulted into a pleasant limoncello. Not the best I could imagine [I blame it to the lemons, which were far from superior] - however nice, fresh and clean tasting.

I will report in a few months, how the other method is working - looking forward to try more lemon flavored hooch!