Wild Fermentation Is the Sexiest and Least Understood Part of Spirits Making

Rums Raw Materials Where Wild Yeasts can be Found

     It's one of the most divisive areas in spirit making. Fermentation, by either wild or with industrial yeasts, has become synonymous with the battle between all that is natural, and the convenience and consistency of man-made machination. 

For some, the thought of using "industrial" yeast cultures to ferment spirits is truly faking it.    They claim that adding these yeasts, deliberately bred to impart desired flavors to spirits, is a betrayal of the concept of terroir - the concept that spirits should taste of the place the sugarcane is grown.

     Others claim that the risks involved in allowing "natural" yeasts to carry out the ferment are unacceptable, and can lead to faulty or weird spirits. They scorn the idea that native yeasts are part of terroir, arguing that most wild ferments are carried out by commercial strains resident in the distillery. 

Comercialy Produced Yeast

     We sometimes forget that, like cheese, spirits are a microbiological product. The Molasses and other materials get all the glory, but that isn't very fair.  Spirits are a product of fermentation.   The process by which yeasts turn sugar into alcohol and yields energy.   Afterward, there's a second bacterial fermentation, called malolactic fermentation, that exists in most spirits. This adjusts their acidity and makes them more stable.

     Yeasts are tiny. We can't see them, and the only evidence of their activity is a steady stream of small bubbles of carbon dioxide rising to the surface of fermenting wash. But what they do is astonishing.   They transform simple, sweet-tasting sugars into something much more complex, a liquid that has the potential to be profound, and which, with its alcoholic content that after distillation will become your favorite spirit.

     Freshly harvested sugar cane or molasses contain pretty much all that is needed to make a great wash. They have enough sugar for yeasts to make enough alcohol to keep the wash stable, and enough acidity to make it taste fresh and preserve it.  

     Active dried yeasts, a midcentury modernization of 19th-century pure starter cultures, took off soon thereafter, especially among New World distillers. They took a lot of the risk out of fermentation and, in the New World, where spirit production was accelerating, the demand was for clean, attractive spirits commercial yeasts promised distillers a much clearer route to this goal than relying on the raw materials alone.

     I'm glad that wild fermentations are more common these days, and that there is a link between the organisms that carry out these fermentations and the farms that produce the raw materials.  But I'm also grateful for the sophisticated microbiological work carried out by yeast researchers, resulting in interesting products, such as specialty yeast strains and even cultured non-Saccharomyces yeasts for those who want wild ferment character without the risk. Both are necessary, and in the right hands can help make more interesting spirits.