What is it that Yeast Really Does in Rum Making?

Filling the Fermenter with Molasses

     Water, a derivative of the sugar cane and yeast, one of the three raw materials needed to make

Rum, but can it have an impact on the flavor of the rum?   Function or flavor?  Yeast’s primary role in rum-making is to ferment sugar and produce alcohol. 

     It’s not as simple as who is right. You need yeast to make rum. It is one of the three elements permitted in rules to make rum. The question is does the yeast used have a direct effect on specific flavors in the new rum?  There are different opinions on this subject depending on where in the world and what type of spirit you are making.  American Bourbon producers and the Japanese will use strains unique to their distillery.

Fermentation Underway

     Yeast is a single-celled fungus which comes in a multitude of different species.  Distillers have been known to go to extremes when it comes to their yeasts, even to the point of guarding them and their strain as a proprietary part of their spirit.   Distillers have learned to utilize yeast’s ability to mutate and be bred in such a manner that will produce specific aromas.   In all cases, the yeast eats the sugar and produces alcohol, carbon dioxide and heat, but in this process flavors are created.

     “The species isolated and used by the industry are called Saccharomyces cerevisiae, but there are many strains of this, all of which give different flavor profiles – a Champagne yeast will be different to a red wine yeast, while the multitude of yeasts used by brewers are key to the huge range of different flavors produced in beer and wine.  Yeast is also continually breaking down sugars and proteins into amino acids, these are the building blocks of flavors.  This chemical reaction is the basis of individual flavor, and yeasts can be bred to enhance specific elements that create these flavors.”

There is a very complete article on this subject that was very well written by the “Whiskey Professor at https://scotchwhisky.com/magazine/ask-the-professor/15315/does-yeast-affect-the-flavour-of-whisky/ .   You might want to give this article a good look if you are interested in the subject.

Heavy Duty Fermentation as Yeast is in Action

     Richard Seale, a well known Rum producer, made the following comments about the subject.  “People are often surprised that we do not boast our very own ‘proprietary yeast strain’ like every other rum distiller does to stale effect.  Sorry to disappoint, our approach is more akin to our Scottish brethren.”   “I was visiting a Bourbon distillery in Kentucky recently and was told how important yeast was in the making of their flavor. But, when I asked the same question in Scotland, I was told that yeast didn’t make a difference at all. Who is right?”

     This is a subject that has been up for debate since the beginning of time when It comes to spirit production.  I personally feel like there might be something there, but there are things that make a bigger impact on how the finished product tastes and smells.