[Ed note: As senior editor Paul Adams reported and wrote his soda story, editor in chief Dan Souza began developing his own recipes for the home cook. The following is from his perspective.]
Most of the time when I’m thinking deeply about beverages there’s alcohol involved. When I decided to develop a couple of soda recipes to accompany Paul’s lovely deep dive into flavored beverages and bubbles, I was worried I might find soft drinks a bit. . . sober. Among its other dazzling properties, alcohol is a great carrier of flavor, which is why boozy drinks can taste so delightfully intense. But when I removed alcohol from the equation, I found myself focusing more deeply on other, surprising elements of flavor. And when it comes to soda, flavor is everything.
I set my sights on two combinations: lemon-lime and strawberry-rhubarb. Step one: Create a flavorful base using (mostly) fresh ingredients. (No allyl caproate here.) Step two: play with carbonation.
Darcy O’Neil, chemist turned bartender turned soda expert, explains in his book Fix the Pumps that the first popular soda fountain flavor was lemon. Lemonade was a fashionable beverage around the turn of the 19th century, so it stands to reason that a carbonated version of it would be equally a la mode. But O’Neil explains that that wasn’t the whole story. Lemon was popular with soda jerks (who operated the soda fountains) and pharmacists (the original soda makers) in a large part because lemon peel is saturated with flavor-packed oils, which have a long shelf life once extracted (citrus juice, on the other hand, deteriorates rapidly and, thus, has no place in syrup). A strawberry tastes great, but it has no oily peel, so its flavor is all in a watery form that’s only good when very fresh.
I wanted to riff on the original fashionable soda flavor, as well as one of most enduring bottled sodas of all time (I’m looking at you, Sprite) by incorporating lime and then adding some welcome intensity with a couple of secret ingredients. I chose to take my lemon-lime soda into double lemon-lime territory (!) by adding makrut (also known as kaffir) lime leaves and lemon grass. Fresh makrut lime leaves (which are easy to buy online in small quantities) have a resinous, concentrated lime aroma that serves them well in curries, soups, and stews in Southeast Asian cuisines. And accurately named lemon grass is a grass with a lemony aroma, also popular in tropical parts of Asia.
To make a concentrated syrup, I combined lemon and lime zest, lemon grass stalk, and lime leaves with water and sugar, brought it to just a simmer on the stove, turned off the heat, and let it steep, covered. I wanted enough heat to speed extraction but not so much that would damage delicate volatile aromas, or drive them into the air and out of the syrup. After straining, I was left with an intensely heady, lemon-lime syrup. And, while it made for a lovely, aromatic soda when I added soda water to the mix, it lacked the citrusy acidity I wanted. This soda needed a bit of a pucker. I solved the problem by adding a dry acid that I ordered (easily!) online, one that you often see listed on the back of a can of soda (for good reason, it turns out): citric acid. Citric acid added sharpness and made the soda taste more like lemon and lime.
There may be no flavor combination more near and dear to my heart than strawberry and rhubarb. I come from a family of Mainers and pie makers and a childhood home with a rhubarb plant the size of a Volkswagen Beetle. But I’ve never had a strawberry-rhubarb soda. And I really wanted one. I love the combination of jammy, stewed strawberries and rhubarb in pie filling. But when it came to adapting the pair for soda, I knew I wanted fresh, not cooked, flavor.
Unlike citrus peels, lime leaves, and lemon grass, strawberries and rhubarb aren’t loaded with flavor-packed oils that can be extracted into a concentrated syrup through gentle heat. To get the experience of eating a fresh strawberry combined with the brilliant acidity and astringency of raw rhubarb I would need to carbonate their uncooked juice. Rhubarb is easy to juice and I had quick success blending or food processing it into a puree and then straining it through cheesecloth. But try blending and straining strawberries to get their juice and you end up with a pulpy, gelatinous mass that simply refuses to give up its liquid. If you have a centrifuge, you can go the route of the guys over at ChefSteps and rapidly separate out the juice from the pulp. I don’t have a centrifuge (I know I’m not alone here), so I wanted a lower-tech solution to the problem. I reached out to someone I figured may have already come up with it: Evan Harrison, part owner and bar manager at Mamaleh’s Delicatessen in Cambridge, Massachusetts.
Harrison’s background is behind the bar, but at Mamaleh’s, he’s stepped up to the fountain, so to speak, and created 13 house-made sodas. My favorite is his pineapple lactart (lactart is a natural milk-derived acid that adds a pleasant sourness to sodas, and was marketed for this purpose in the 1880s). The soda is crystal clear with the faintest yellow hue, but it’s absolutely bursting with intense fresh pineapple flavor. I called him up and asked him how he does it. Harrison explained that he combines fresh pineapple with sugar, seals it in a vacuum bag, and stores it in the refrigerator for up to 6 days. Through the power of osmosis, water in the pineapple is drawn out of the fruit and into the sugar-rich syrup in the bag. Then he muddles the mixture by hand before straining off the syrup. In the kitchen we call that maceration, but it’s usually done on a much shorter time scale—letting the fruit and sugar sit together for only 30 to 60 minutes—and with the goal of pulling excess liquid from the fruit, not infusing the fruit flavor into the liquid. But it made sense. Infusion doesn’t only happen when heat is applied, it just happens faster with heat. (Think about the brewing time difference for cold-brewed and hot-brewed coffee.) Leaving the exuded juice in contact with the fruit for an extended period of time allowed it to pick up lots of fresh flavor.
I tried it with my strawberries. I tossed a pound of sliced berries with some sugar, popped them in a zipper-lock bag, and let them macerate for different lengths of time, from 30 minutes (at room temperature) to up to 4 days (in the fridge). The same-day batches had weak flavor, but after 12 hours the syrups were delicious. All I had to do then was strain the syrup through cheesecloth (and reserve the nice macerated berries for topping yogurt or oatmeal), combine it with my rhubarb juice, and carbonate. There was no need for lactart (or citric, malic, or tartaric acid, for that matter) because rhubarb is packed with its own bright acidity.