This test is as scientific as I’m able to conduct at home. I used the exact same materials, time, lemons, etc. for both halves of one batch. The only difference was filtering the liquor. I wanted to see what kind of difference, if any, liquor filtration has on the final product. Here are the ingredients for the whole experiment.
Liquor: Two 750ml bottles of Everclear 151
Liquor filtration: Varies
Lemons: 17 Non-organic, waxed and scrubbed
Days peels and liquor rested: 55
Simple Syrup – Cups Sugar: 4, Cups Water: 5
Days syrup rested with infusion: 48
Final filtration: 4x
Just after zesting the lemons, I divided the zest into two even halves and put each half into an identical glass jar. I then poured one unfiltered bottle of grain alcohol in one jar and the other jar received an identical bottle of alcohol but after 4 filtrations in the Brita filtering pitcher. Everything else was identical down to the amount of time I waited to taste them and the temperature of the Limoncello at tasting.
The results for the first, unfiltered, half are:
As you can see, it’s fairly rough stuff. It’s pretty sweet, which offsets the harshness in the flavor somewhat but it has a lot of heat and is a very rough Limoncello. Drinkable but not great.
Here are the results of the second half of the batch:
As you can clearly see, the results were very different this time. The smoothness of this half of the batch was a world of difference from the unfiltered half. Compared to this half, the unfiltered half feels like getting punched in the throat. This one is smooth and silky with a little bit of heat and both halves had some off flavors on the finish that were probably due to the fact that I couldn’t use organic lemons and/or didn’t scrub them hard enough. Because of the smoothness, the sweetness of the Limoncello is more apparent which is why I rated this one as more sweet despite the fact that the two halves contain exactly the same amount of sugar.
With this direct comparison under my belt, I can tell you with absolutely no reservations that filtering the liquor makes a HUGE difference in the smoothness of the final product. Since this batch was created I’ve made a couple others and forgotten to filter the liquor. I’m now acutely regretting that. I strongly recommend that you filter the liquor before the infusion with the lemon zest. I plan future tests to see where the point of diminishing returns is on filtration. Less filtration is faster but if I could double the smoothness by filtering the liquor 8 times, I’d do it. It’s still much faster than letting the finished Limoncello rest for a year or two, which is what I’ll need to do with the unfiltered half.