Limoncello physics

August 17, 2011 7:49 AM

First attempt at making limoncello. We're trying this on the cheap, using 44% abv vodka instead of grain alcohol, "just to see what happens". What happened is strange....

Following this recipe, now 60 days into the 90 day process. After adding simple syrup (625 g) to 650g of alcohol+zest, the liquid tastes like limoncello, all right, but why is there stratification in the bottle, now 7 days after addition of the simple syrup? There are four distinct layers in there and they survived a move from the place of repose onto the counter where sunlight shows the murky mid-level.

Is there another kitchen-equipment-only experiment that will reveal the reason for the stratification?

posted by jet_silver to Food & Drink (5 answers total)

My wife and I have made about 6 batches of limoncello in the past 6 months or so, but we've never cut the peels so small. It looks like you used a zester, where we used a vegetable peeler. My guess is that there is more tiny pieces of lemon that will float easier now that you've added the simple syrup.

I imagine that in the end this won't matter much once you strain the peels out and the liquid will be more consistent.
posted by schyler523 at 8:07 AM on August 17, 2011

schyler523 seems correct to me. I get a little stratification pre-straining but it's not that dramatic.

For what it's worth, I use vodka and a vegetable peeler. And sometimes I add fresh rosemary.
posted by cranberry_nut at 8:29 AM on August 17, 2011

Best answer: The layers are caused by insoluble parts of the mix. Since lemon juice, lemon oil, and sugars are all soluble in alcohol/water mixes, you're looking at stratified cells, cell remnants, proteins... stuff that doesn't really contribute to flavor anyway. Strain the liquid through a coffee filter to clarify at the end of the process.

At 88-proof, there's nothing growing in there.
posted by IAmBroom at 8:36 AM on August 17, 2011 [3 favorites]

When I've made limoncello (with a zester, not a peeler) I've always filtered it before adding syrup, and always kept shaking it up before then, rather than looking at the layers. Still, the middle layer in your picture looks like the haze that would be left behind if you don't filter well.

I like to first filter out the zest with a mesh strainer (go ahead and squeeze out any more liquid from them) so it won't slow down later flitering, then run it through a coffee filter to take out the hazy sediment. The coffee filter is slow and a bit of liquid will be left behind, but don't rush it or squeeze out more liquor, or the haze particles will come through. Not sure if the syrup-added, and thus more viscous, liquor will filter more slowly.

Also, I've added much less syrup than you did when making limoncello with 80 proof vodka, compensating by making it fairly sweet syrup, to avoid lowering the %abv too much since I wasn't starting with higher proof grain alcohol. A 500 g batch of vodka+zest gets mixed with 120 g of sugar dissolved in 80g of boiling water. Aiming for something around 60 proof, rather than 40 proof.
posted by JiBB at 11:09 AM on August 17, 2011

Response by poster: The reason for the density gradient is very puzzling but this time-lapse video (warning, I didn't know how to put the camera in manual focus) shows the gradient is real. The layers don't mix even when driven by a good-sized thermal gradient across the width of the container; rather, you can see the circulation within bands.

On stirring this up quite thoroughly and waiting 72 hr what's left is a remarkably clear liquid with tiny but agglomerating and descending particles, plus a layer of peelings.

Thanks for the various thoughts.
posted by jet_silver at 8:00 PM on August 24, 2011