I wanna come down from this cloud

April 7, 2011 11:01 AM

Why is my lemoncello cloudy? When I combine the simple sugar and the lemon infused alcohol, both of which are very transparent (although one is a luminous yellow) the resulting mixture becomes instantly cloudy. Can anyone explain why? For bonus points can you suggest a way to minimize this?

Commercial lemoncellos are quite clear, so I know that it is possible. In case the details are important, I will describe my basic process in some detail:

I take 190 proof grain alcohol and pass it through a Brita filter as many times as I have the patience for (normally five). I then make an infusion with lemon peel, which is either zested or peeled with a veggie peeler and let that soak for a month or so. I then make a simple syrup with a roughly 5:4 ratio of distilled water to cane sugar, which becomes perfectly clear when I heat it. I filter out the lemon peel with repeated passes through a coffee filter (usually five passes)

However, as soon as I introduce even a small amount of the syrup to the alcohol, the brilliant transparent yellow alcohol turns to a cloudy yellow mixture. I find that the liquid sometimes becomes clear again after many, many months, but not always. I've noticed that zested lemon liquor is more cloudy than peeled and I know that if you only let the lemon infuse for a short period this doesn't happen (but it also doesn't taste nearly as good).

posted by Lame_username to food & drink (25 answers total)

Do you cool the sugar syrup completely before adding it to the limoncello? Supposedly the temperature of the sugar syrup makes a big difference.
posted by Ery at 11:07 AM on April 7, 2011

Homemade limoncello contains terpenes, a class of volatile organic compounds that are soluble in 30% ethanol or higher mixtures. Once you dilute the solution to less than 30% alcohol, they fall out of solution – what you see as "cloudy" is the precipitate. Read more.
posted by halogen at 11:08 AM on April 7, 2011 [4 favorites]

This thread has more information about louching limoncello. They suggest diluting the lemon and alcohol mixture with more alcohol to correct the problem.
posted by Lycaste at 11:10 AM on April 7, 2011

According to posts on this forum, terpenes are removed from commercially sold liqueurs, which makes the product better-tasting and increases shelf-life. Do you have access to a centrifuge?
posted by halogen at 11:11 AM on April 7, 2011 [1 favorite]

You could try infusing in the alcohol/simple syrup mixture initially. Prep the solution you want and that insolubles won't extract in the first place. You may need a longer contact with the peel though.
posted by bonehead at 11:18 AM on April 7, 2011

halogen and lycaste are correct. Add Pastis or Pernod to water to see the effect in action.
posted by JPD at 11:19 AM on April 7, 2011

Could you try adding alcohol to the syrup instead of syrup to the alcohol?
posted by maryr at 11:20 AM on April 7, 2011

I've had many, many a "house-made" limoncello at different restaurants and friends' homes, and though their commercial counterparts are not, the house spirits are almost all a bit cloudy.
posted by brand-gnu at 11:21 AM on April 7, 2011

Halogen, the only thing that bothers me with your explanation is that I can add less than a cup of simple sugar and see the effect take place. At that point, the mixture is still 75% alcohol or more. I already have a fancy ph meter for some of my other projects, I fear that if I purchase a centrifuge my family will have me committed. Although they will drink my lemoncello first. I'm curious as to the idea that it tastes better with the terpenes removed, because I've never had a commercial batch that comes close to my homemade stuff, but I use a ton more lemon than most recipes call for.

Ery, I have experimented with different temps. I do think that cool syrup reacts more slowly, so perhaps there are multiple factors at play.
posted by Lame_username at 11:32 AM on April 7, 2011

Lycaste, that thread is awesome. Now I can just tell people its the louche, which is in the good stuff. The power of the hive mind always amazes me. Now I've found more web forums with kindred spirits. Thanks, all!
posted by Lame_username at 11:36 AM on April 7, 2011

Could you try adding alcohol to the syrup instead of syrup to the alcohol?

Won't make a difference. This is a solution equilibrium effect (mostly), not a kinetic (ie transient) one.

The culprit, as much as anything is the high concentration of sugar. It's altering the ionic strength and proticity of the solution a lot, enough to knock the highly polar and protic terpanoids (and probably even the steroids) out of solution.
posted by bonehead at 11:53 AM on April 7, 2011

Let your limoncello rest for about 40 days and the cloudiness will precipitate out. Move your jug to your workspace a couple days before you decant and use a siphon. The slightest little jiggle will stir it up again. MMMMM! homemade limoncello!
posted by Pecantree at 11:53 AM on April 7, 2011

(sorry, sterols, not steroids)
posted by bonehead at 11:54 AM on April 7, 2011

Every homemade limoncello that I drank in the south of Italy, its country of origin, has been cloudy. Even the bar-bought one is cloudy. The color varies from pale yellow to deep almost orange yellow, depending on the variety of citrus used. Congratulations in making real limoncello.
posted by francesca too at 12:44 PM on April 7, 2011

I like bonehead's idea. Why don't you try a batch where you mix the simple syrup with the alcohol, then add the lemon peel and infuse. Might produce clear limoncello!
posted by exphysicist345 at 12:58 PM on April 7, 2011

Let your limoncello rest for about 40 days and the cloudiness will precipitate out.

Funny thing is sometimes yes, sometimes no. I do know that when I make it with 100 proof vodka instead of 190 proof grain that it clears up much faster and more readily. This is either because the grain extracts more of the terpanoids or because I dilute the vodka with about half as much sugar water. Either way, the results with the vodka are very much inferior to the results with the grain because it tastes less lemony.
posted by Lame_username at 12:59 PM on April 7, 2011

Halogen, the only thing that bothers me with your explanation is that I can add less than a cup of simple sugar and see the effect take place. At that point, the mixture is still 75% alcohol or more.

A lot of the alcohol is working on dissolving the sugar, which means it isn't available any longer to dissolve the terpenes.
posted by Chocolate Pickle at 1:02 PM on April 7, 2011

I like bonehead's idea. Why don't you try a batch where you mix the simple syrup with the alcohol, then add the lemon peel and infuse. Might produce clear limoncello!

I am going to try that, although I know from experience that filtering after the sugar is mixed into the solution is much more tedious than filtering before. The sugar rich solution doesn't really like to flow through coffee filters. I also fear that it might extract less lemon flavor, but at the rate we go through the stuff, I'll get a chance to give it a go soon enough and learn for certain.

I'm also something of a mad scientist of using different citrus fruits. Orange is good, key lime is better. Adding a bit of pineapple to the lemon peel adds a very interesting touch that no one ever recognizes for what it is, but they always like.
posted by Lame_username at 1:03 PM on April 7, 2011

A lot of the alcohol is working on dissolving the sugar, which means it isn't available any longer to dissolve the terpenes.

Ah, I see. While I have the attention of you chemical geniuses, is some version of this the reason that the flavor improves dramatically with age? When the batch is first blended, the alcohol punch is extremely strong and provides a grappa like burn. Over time, the flavors "blend" and the bite is dramatically reduced. By 6-8 months of age, the flavor is amazingly smooth, almost as if there is no alcohol at all. Is the alcohol slowly bonding with the sugars over time?
posted by Lame_username at 1:07 PM on April 7, 2011

I also fear that it might extract less lemon flavor

I think this is a pretty safe bet. It may also reduce a lot of the harshness of things like the limonenes too though.

Filtering through paper is also going to knock out a lot of flavour in my experience as well. Could you use a jelly bag or a gold foil coffee filter instead? A little more expensive, but also reusable.
posted by bonehead at 1:33 PM on April 7, 2011

When something like sugar is in solution, each sugar molecule is surrounded by a bunch of solvent molecules. But there isn't any chemical reaction; it's just charge attraction. The "solution" aspect comes from the fact that the solvent separates all the sugar molecules from each other.

Precipitation happens when there isn't enough solvent present to do that, so sugar molecules (or terpenes) come together to form larger globs. That, too, isn't a chemical reaction; it, too, is simply charge attraction. Molecules like this have sections on their surfaces which are positively charged and sections which are negatively charged.

The reason that water and ammonia are such good solvents is that they act like itty bitty bar magnets, which are positively charged on one side and negatively charged on the other, which makes them especially good at getting in between the molecules of the thing being dissolved and keeping those molecules apart so they can't form larger globs.

I don't know what it is that changes as your stuff ages, but it wouldn't be an alcohol/sugar chemical reaction, because there isn't any, really.
posted by Chocolate Pickle at 1:35 PM on April 7, 2011

Is the alcohol slowly bonding with the sugars over time?

That is not what happens. There are, however, complex chemical reactions going on with all the other organic compounds in your limoncello, including the above-mentioned terpenes, various phenolic compounds (think essential oils), and the sugars. You may feel less "sting" due to alcohol forming esters with acids, which makes the drink less acidic.
posted by halogen at 1:50 PM on April 7, 2011

I'll confirm what other people already said, every homemade limoncello that I've seen in Italy, and I've seen a lot, always looks cloudy to some degree (and it's a bit thicker too). That just is the mark of traditional homemade limoncello vs commercial ones.
posted by bitteschoen at 1:56 PM on April 7, 2011

Filtering through paper is also going to knock out a lot of flavour in my experience as well. Could you use a jelly bag or a gold foil coffee filter instead? A little more expensive, but also reusable.

Interesting. When I've used the gold filter, I tend to get a little line of scum at the top of the bottle and what I imagine to be a harsher flavor. That is something I've experimented with and I prefer the flavor of the more heavily filtered stuff, although I've basically doubled the amount of lemons compared to most any recipe I've seen.
posted by Lame_username at 2:21 PM on April 7, 2011

The predominant terpene in citrus peel is limonene, which is mainly responsible for the fragrance. It's practically insoluble in water, which makes it a good candidate for the cause of the cloudiness of your limoncello.

Its melting point is -74C and its boiling point is ~175C, so you'll never get it out of there by freezing or boiling.

I was extremely surprised to read that limonene's "a selective adenosine A2A receptor agonist", because caffeine's neurological effects are most often attributed to the fact that it is a non-selective adenosine antagonist. I wasn't able to find any information about how they act when they're used together, but I might guess that orange juice may eventually be found to owe it's traditional place on the breakfast table to an ability to ameliorate some of the less desirable effects of our morning coffee.

The bitterness of citrus peels is supposedly primarily due to limonin, a triterpenoid and a much larger molecule than limonene. I'd bet degradation of limonin over time is responsible for the mellowing of your limoncello. Limonin is slightly soluble in water and has a melting point of 298C. I wonder if you could freeze it out and really shorten the time you have to wait to enjoy perfectly mellow limoncello (plus, if it gets degraded through reduction by hydrogen atoms donated from the ethanol, as all those oxygens might lead a person to suspect, then you'd have less acetaldehyde in the finished product, and possibly a superior flavor).
posted by jamjam at 5:40 PM on April 7, 2011