Serious Eats: Drinks

A No-Heat, No-Filter Technique for Making Cocktail Syrups

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[Photos: Kevin Liu]

So you've decided to try your hand at stirring up a few classic cocktails at home. Maybe you started with the Manhattan—a drink that requires only three ingredients, all simply dispensed from shelf-stable(ish) bottles. Then you probably moved on to sours and started juicing fresh citrus. But you're ready to get creative, so you decide to try making a few signature syrups for, say, a Gimlet or a nice punch.

But making syrups from scratch is a pain in the butt, isn't it? First, you have to mince/zest your ingredients up into tiny bits. Next, you're stuck waiting as you cook your syrup to make sure the pot doesn't overflow or dry out. Then after all that, there's a painful process of straining and filtering—and you still might end up with a cloudy syrup.

There's a better way.

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I learned this simple trick from a post by clever bartender Jeffrey Morgenthaler. He wrote about how he vacuum-sealed lemon peels with granulated sugar to create oleo saccharum—a type of strongly-flavored sugar syrup often used in classic punch recipes.

Although both Morgenthaler's method and our own Michael Dietsch's techniques for making oleo saccharum are pretty straightforward (Michael recommends muddling the peels with sugar first and then allowing to sit for about 30 minutes) I wondered if the technique could be simplified even further and applied to more than just lemon peels.

Here's the science. The basic mechanism at work here appears to be osmosis: the tendency for liquid to move from areas of low solute concentration to areas of high solute concentration. It's the same reason that salting a piece of meat will draw liquid to its surface. With syrups, sugar draws the liquid out of fruits and vegetables, and with these guys, aromatic oils join in on the flavor party.

Although Morgenthaler's original technique calls for vacuum sealing the flavoring ingredients in special bags, you don't actually need to use a vacuum to get osmosis to happen. I chose to use zip-top bags because they allow for easy contact between sugar and peels, but you could also use simply stir all your ingredients and leave them in a sealed container. Just make sure that the container is really sealed so that you've trapped all those tasty aromatics.

I decided to try this technique with a few of my favorite flavors that also happen to be my least favorite ingredients to deal with when making syrups the traditional way. Many syrup recipes call for zesting lemon and lime peels with a microplane. But fine zesting causes a ton of the oils to be lost into the air (and onto your microplane). I also thinly sliced some peeled cucumbers and ginger and bagged them with sugar because I love the flavors these ingredients add to cocktails, but it's almost impossible to strain the fibers from these guys if you muddle or mince them in any way. Plus, the complex flavors of both cucumber and ginger don't hold up well to heat (more on that later).

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I haven't had a chance to really refine the exact amounts of ingredient versus sugar yet. I basically just tossed some of the ingredients into a zip-top bag, then added enough sugar to cover everything. I did, however, take notes:

4 large limes = 50g peels, to which I added 75g demerara sugar
4 medium lemons = 50g peels, to which I added 100g granulated white sugar
one hunk of ginger = 70g, to which I added 75g demerara sugar
half a cucumber = 120g, to which I added 60g of granulated white sugar

After combining, I left the baggies on the counter for 4 hours and then checked on them. The cucumbers turned to syrup almost immediately, but it took another 4 hours for the other ingredients to really liquify.

As you can see from the image above, the lemon peels dissolved almost all their sugar. The lime syrup, however, stayed partially crystallized even though I used less sugar.

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Luckily, it was pretty straightforward to add a little water to the bag and dissolve the rest of the sugar.

The lemon and lime syrups tasted exactly how you might expect: intensely-flavored, sweet, and aromatic. Both were perfect for use in a punch, but a bit more thick than is practical for mixing drinks with, so I would recommend adding a little water until the consistency is what you need.

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The cucumber and ginger syrups were the most successful. The cucumbers practically melted before my eyes and released a crystal-clear syrup (pictured above) that tasted both fresh and subtly salty with a bit of umami. Ginger took a bit longer, but the end result was worth waiting for. The syrup had a complex vegetal component absent from most cooked versions. Kind of like cucumber, but with a tinge of green pepper and the earthiness of a turnip.

As far as 'spice' goes, uncooked ginger syrup maintains the pungency of cooked ginger without any of its characteristic burn. I geeked out on this a while back, and found that Harold McGee explained it best: Fresh ginger contains a spicy chemical called gingerol. Unfortunately, if you cook gingerol, it degrades over time into a less-spicy chemical called zingerone. But, here's the interesting part: cooking gingerol also produces shogaol, a very spicy chemical that can be compared to the burn of capsaicin.

So, both fresh ginger syrup and cooked ginger syrup can deliver a punch of pungency, but the chemicals in play are different, so the exact taste and feel of the spice will vary depending on your technique.

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One more thing: don't forget that although sugar sucks much of the goodness out of your peels and sliced veggies, the leftover bits can be used to make a cool garnish. Simply toss the slices into a low oven until they dehydrate, and you'll be left with candied, crunchy, slices of ginger (or whatever you started with.)

I can't wait to try this technique with other finicky fruits once they come back into season. I'm thinking peaches and berries, but I'd love to hear your thoughts.

What homemade syrups give you the most trouble? If you could turn anything into a cocktail syrup, what would you use?

About the author:Kevin Liu likes to drink science and study cocktails. Wait, that's backward. Ask him geeky food and booze questions on twitter @kevinkliu. While you're at it, check out his book about cocktail science.

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