Trends come and go, but the fizzy art of fermentation is alive and evolving.

Fermentation—the breakdown of organic matter by bacteria and yeast— has always played a role in drinks; it’s the process that turns grape juice into wine and puts the alcohol in beer. But lately, bartenders have been pushing their cocktails into unchartered flavour territory with sour kefirs, funky kombuchas and salt-brined tomato cordials. 

As Massimo Zitti of Mother Cocktail Bar has discovered, just a few tannic drops of lacto-fermented concord grapes turn a regular old-fashioned into some – thing weirdly complex and wonderful. For some, the process of transforming local peaches into bottle-conditioned bellinis, as Kelsey Ramage and Iain Griffiths do at Supernova Ballroom, is part of a larger eco-conscious mission to make a sustainable bar program. For others, it’s a personal challenge. “I know it sounds cocky, but it’s been a long time since I’ve tested a drink and failed,” says Stillife’s Andrew Whibley. “Just because you know how to make a Manhattan doesn’t mean you know the first thing about fermentation.” 

The health benefits are on point with the mindful drinking movement. “The good bacteria and living ingredients from garden and kitchen scraps give us just what we need to feel connected to the cocktail,” says Lauren Mote, co-owner of Bittered Sling Bitters. 

But the methods can be dangerous. “Botulism is a real thing,” says Whibley. “You don’t want to make your guests sick.” You don’t want to freak them out either, says Zitti, who adds that the real challenge is making balanced drinks with living ingredients that are constantly changing. “Clementines can taste like lemon when they are fermented,” says Zitti. “But they can also taste like vinegar if you let it go too far.” Ultimately, the risk of working with unpredictable organisms is also its own reward. 

“Fermentation was born from an ancient need—to keep food from rotting,” says Zitti. “But we are working with living cultures. And if we don’t take care of them, they will die. Our drinks are more than just drinks. They show how much we care.”