For all their bad rap as the source of our modern poor health, sodas can be surprisingly old-fashioned. Sure, nowadays they're pumped full of modern additions like high fructose corn syrup. But their origins are almost confusingly antiquated. Dr. Pepper is supposed to taste like prunes? Colas were flavored with some kola nut in the 19th century? And what exactly is tonic water made of, anyway?
I recently learned the answer to the latter question firsthand. Tonic gets its characteristic bitter edge from quinine, a compound found in the South American cinchona tree. Quinine helps ward off malaria infection, making it a favorite drink in tropical climates. The amounts of quinine needed for effective protection were pretty steep, leading to a drink so bitter that Brits with the East India Company decided that you really needed a good lashing of gin to make it go down. I'm not one to argue. The floral/piney notes of gin's juniper berries work well against tonic's bitter edge (and a wedge of lime, in my opinion, makes everything better). Like most cocktail drinkers, I love a good g&t on a hot day. And we've certainly been having a lot of hot days lately. But since I'm not really a fan of high fructose corn syrup, I decided to brew my own.
It turns out that homemade tonic is surprisingly easy. And delicious. The hardest part is securing the cinchona bark--I picked mine up from a local produce market with a huge bulk section (or, rather, I meant to but ended up filching it from a friend because the market was on back-order), but it's easy to find online. The concentrate keeps for several weeks in the fridge (more if you make the simple syrup separately, but that involves too many containers for my lazy self). In addition to simmering the quinine out of cinchona bark, you also add the juice and rind of several types of citrus, a pile of lemongrass, and a scattering of spices. I keep meaning to bring this as a gift to summertime parties, but I end up hoarding it all to myself. I don't know how this stacks up to "traditional" tonic water, but I'd venture to say the Raj never had it so good.
Tonic Water Concentrate
adapted from Portland's own Jeffrey Morganthaler
yields ~5 cups concentrate
This recipe is adaptable -- you can swap allspice berries for the coriander and cardamom (as in the additional recipe), or substitute grapefruit for the other citrus (a nice variation). I've tried this twice with cinchona from different sources, and the results have varied (and, surprisingly, the shredded bark ended up more potent than the powder). The lower amount of cinchona ensures that it doesn't overwhelm the other flavors, but if you favor the bitter, have a less-potent cinchona, or just need something to cut through the heat, go with the larger amount.
4 cups water
1 cup coarsely chopped lemongrass (~4 stalks)
3/4-1 ounce cinchona bark (see note above)
12 caradamom pods, bruised
1 tsp whole coriander seeds
zest and juice of 1 orange
zest and juice of 1 lemon
zest and juice of 1 lime
1/4 cup citric acid
1/4 tsp coarse salt
3 cups sugar
Toss all ingredients except the sugar in a pot, bring to a boil, and reduce heat until it just maintains a simmer. Simmer, covered, for 20 minutes. Let cool, and pour through a cheesecloth-lined strainer (you can also pour through a coffee filter if you like, depending on how much sediment remains and how clear you like your beverages). Place back on the stove, and add the sugar and an additional 1 cup water. Heat and stir until the sugar is dissolved. Taste, and add more sugar if needed (note: this is difficult to taste on its own, so you might need to pour a bit into some soda water to get a good read on the finished product). Pour into jars and chill.
To serve: Pour an icy glass of soda water, and stir in enough tonic concentrate to suit your taste (this is generally just a few tablespoons). Gin and lime optional, though highly recommended.