Bartenders around the world use fermentation as a unique way to express an ingredient's flavor in a cocktail, not merely as a method of preservation. Lacto-fermentation, specifically, can transform what was once a sweet peach into a creamy umami-driven ingredient that challenges what people understood that food to be, creating a memorable drinking experience. For innovative bartenders who enjoy experimenting with new acid sources and unique flavors, lacto-fermentation delivers on both fronts.
What Is Lacto-Fermentation?
Fermentation can be defined as the chemical breakdown and transformation of organic matter by microorganisms and other microbiological factors such as yeast, bacteria and enzymes into acid, gas or alcohol. Lacto-fermentation, specifically, uses lactic-acid-producing bacteria (LAB), primarily from the lactobacillus genus, to break down the sugars in food to create lactic acid, carbon dioxide and sometimes alcohol.
It’s also one of the least-complicated types of fermentation: All you need is salt, sugar (typically in the form of a vegetable or fruit) and an anaerobic environment (i.e., a Mason jar or a vacuum-sealed plastic bag). The salt keeps unwanted “bad” bacteria from proliferating in the fermentation and ensures that the healthy LAB can do its job properly to create a complexly acidic ingredient.
It’s perhaps the oldest method of food preservation, but bartenders are now harnessing this method to create bespoke ingredients for their boundary-pushing cocktails.
How to Lacto-Ferment
“The process is quite simple,” says Natasha Mesa, the bar manager at Deadshot in Portland, Oregon. “Weigh your ingredient, add [at least] 2% salt by weight [of the food you’re fermenting] and wait. How many days [the fermentation takes] depends on how sour you want the final product to be.”
You’ll want to use noniodized salt and keep it all in a sealed container, ideally a vacuum-sealed bag. Don’t forget to start with clean ingredients but not too clean. “Choose organic ingredients when possible, and avoid washing too thoroughly to ensure you have a healthy population of wild LAB,” says Mesa. “I.e., remove visible dirt by gently rinsing—don't scrub.”
Taking proper safety precautions is crucial, since you’ll want to keep “bad” bacteria out while the LAB do their work. That’s where the salt comes in. Mesa emphasizes the need to salt sufficiently with at least 2% of the ingredient’s weight. “LAB doesn't require salt to flourish, but they do tolerate it, meaning we can use the salt content in a lacto-ferment as further insurance against unwanted outsiders,” she says.
You’ll also want to keep an eye on the acidity. “Get yourself some pH strips. They’re accurate enough to know if you have safe ferments on your hands,” says Derek Stilmann, the bar manager at The Sylvester in Miami and the founder of fermented beverage startup Culture to Culture. A pH lower than 4.4 is considered safe, meaning it’s acidic enough that bad bacteria can’t proliferate.
This is all important because you likely won’t be keeping your ferment in the fridge. “Most ferments do their best and most efficient work at room temperature,” says Mesa. “You can ferment in the fridge, but it just takes much longer.”
Tasting as you go along is important to know when the ferment is done. “If possible, try to taste your ferment every day,” says Mesa. “If you use a vacuum-sealed bag, when you go to burp the bag, taste the product before resealing it. Overfermenting results in the flavor of the product being washed away under a sea of sharp acidity.”
And finally, if a wispy white substance forms on the surface of the liquid and around the edges of your fruit when fermenting in a jar, simply spoon it off. This is known as kahm yeast. “It is harmless but can add an off flavor if it gets distributed into the mix,” says Mesa.
Using Lacto-Fermented Ingredients in Cocktails
There are many ways to use lacto-fermented ingredients in cocktails. While the two main options are using the brine or the fermented food itself, enterprising bartenders are adding their own twists, like running the solid ingredient through a juicer or turning brine into a sherbet. Regardless of how you use the ingredients, it’s important to keep in mind that this ferment adds acid to a cocktail, which will need to be balanced with a sweet component.
The lacto-fermented food can be used in cocktails in a number of ways. But remember that the ingredient’s sugars have been transformed into lactic acid, so it should be used as you would an acid as opposed to a sweetener.
Stilmann says that he uses fermented tomatoes in a Bloody Mary mix to add savory notes and depth of flavor. He lightly chops the tomatoes and adds 2% of their weight in salt, mixes it in a bag and vacuum-seals it. “My rule of thumb for when they're ready is when the bag expands like a balloon, open and reseal it,” he says. “Once it expands again, they’re ready.”
Eric Lorincz, the owner of Kwãnt in London, employs a lacto-fermented purple carrot in his Hacienda cocktail, an elevated riff on the Margarita that also includes Patrón silver tequila, Cocchi Rosa aperitivo, fino sherry, mezcal, agave nectar and freshly squeezed lime juice. He runs the lacto-fermented carrots through a juicer, producing a vibrant savory juice with a light-bodied mouthfeel and acidity almost akin to a vinegar, a clever and unexpected way to use the technique in cocktails.
The brine often contains the flavor of the ingredient that was fermented but is salty and a bit funkier than the fruit or vegetable’s raw form. The liquid is creamy due to the lactic acid, which also adds body and texture in addition to acidity.
At the renowned Connaught bar, the brine from a lacto-fermented melon pairs with Rémy Martin XO cognac, green Chartreuse and London Essence pink pomelo tonic water in the Flint cocktail on the bar’s current menu.
“We were looking for something to oppose the refined taste of cognac, and lacto-fermented melon was the answer,” says Giorgio Bargiani, the head bartender at the Connaught Bar. “It brings freshness and a sour note, latched to yeasty biscuit-like notes that complement and complete the full body of Rémy Martin XO.”
Another easy application for the brine comes in the form of a sherbet, an oleo saccharum with fresh juice added. “[T]he ferment can be used as a sour element to balance a drink or to reduce the sweetness of a certain ingredient,” says Agostino Perrone, the director of mixology at The Connaught Hotel. “We've made a delicious sherbet out of lacto-fermented apple by using the pickling liquid [brine] for the sherbet itself and the fruit to make a garnish to enhance the flavors.”
While sherbets are a great fit for lacto-fermented brines, shrubs are not. Perrone makes the point that using the lacto-fermented brine to create a shrub adds lactic acid to acetic acid, which can result in an unbalanced cocktail.
If you want to use the brine on its own, without crafting it into a separate ingredient, it’s especially effective in stirred cocktails in the place of a syrup. At Deadshot, Mesa uses the brine from a lacto-fermented gherkin in a Dirty Martini riff as part of the umami flavor. In the Super Soup, she employs fermented green tomatoes in a cocktail inspired by Southeast Asian flavors, where the tomatoes are mixed with vodka, gin, a savory syrup, coconut milk and lime juice. The applications are endless—it’s all about balance.