Mention the word “yeast” to Conor O’Driscoll and he lights up like a car with its high beams switched on. O’Driscoll is Heaven Hill’s master distiller and yeast is definitely a subject about which he is passionate. He explains that during fermentation, “The yeast makes all the alcohol and a lot of the flavor.”
Most whiskey lovers appreciate that all of the color of the liquid in their glasses comes from the time the spirit spends in the barrel. The characteristic vanilla and caramel flavor notes, as well as a medley of baking spices, molasses and maple, nuts, and even some chocolate and coffee notes, can be coaxed from the wood. But where do all those lovely fruit and floral flavors come from?
During the visit to the fermentation room on a distillery tour, little is said about yeast when standing by the bubbling tanks other than that it is doing the work of converting the sugars (extracted from the grains thanks to malt enzymes) into alcohol. It may or
