yeast’s Role Yeast, a single-celled organism that multiplies vigorously when exposed to oxygen, plays an essential part in fermentation prior to distillation. After using up all available oxygen, yeast converts sugar into alcohol and carbon dioxide–without this biological process we would never be able to produce alcoholic beverages or even ethanol fuel!
While oak maturation plays a part in shaping the flavor profile of spirits, fermentation of simple sugars into ethanol and other metabolites has an outsized influence on their character. The yeast used during this step plays a pivotal role in controlling aroma intensity (the intensity of each individual odour perceived within a sample) and ester concentrations – two components which contribute significantly to overall flavor profiles in finished spirits.
As such, distillers dedicate considerable resources and effort into finding suitable strains of yeast for their products. Different yeast strains have different methods for breaking down sugars present in mashes into various flavors compounds and other substances, leading to different flavor compounds being released from them.
Saccharomyces cerevisiae yeast, used in ordinary bread baking, breaks down sugar into carbon dioxide and ethanol used to fortify foods and drinks. Unfortunately, high alcohol levels cause this strain of Saccharomyces cerevisiae to die off prematurely, producing unpleasant flavour congeners – so distillers typically utilize other strains of Saccharomyces such as beer yeast varieties, wine varieties or fruit turbo variants for spirit making.
