Either way, there is a “humungous diversity of untapped yeasts” out there, she says. Commercial bakers, for instance, largely rely on standard strains of Saccharomyces cerevisiae. But wild yeasts or historic strains that have fallen out of use could actually be better options for modern production.
“Species of yeast outside Saccharomyces cerevisiae are often more tolerant of things like using frozen dough and sometimes even have increased leavening ability,” says Heil.
Thomas says he wants to sample and study yeast from sealed vessels found on yet more shipwrecks, or other, well-preserved, boozy time capsules. And by studying the genetics of old yeast strains, it might also be possible to identify previously unknown but desirable genes, which could influence genetically modified yeast in the future.
But the wreck of the Wallachia is a sobering reminder of just how lucky we are to have access to a handful of historic yeasts that we can confidently associate with a specific time and place. In the 30 or so years since Hickman has been diving to it, he’s witnessed how the wreck has deteriorated over time. Structures and walkways above and around the engine room have collapsed. Cracks in the ship’s ageing walls have widened. The vessel is fading away.
“I would suspect that, possibly within the next 20 to 30 years, it will be completely gone,” he says.
The Wallachia will likely take its remaining beer bottles with her as she slowly breaks apart on the seabed. A valuable link to the brewers of the 19th Century will finally be gone forever, taking the precious yeasts it carries in various long-forgotten bottles of booze with it.
If you liked this story, sign up for the weekly bbc.com features newsletter, called “The Essential List”. A handpicked selection of stories from BBC Future, Culture, Reel, Worklife, and Travel, delivered to your inbox every Friday.