Yeast is perhaps one of the most overlooked (or perhaps the least spoken about…) ingredients in whisk(e)y distillation. We all know the main contribution of the yeast: Ethanol. I wrote about yeast on my first whisky blog in 2008. But this Summer I learned a lot more about it in the best possible way: Using my nose and mouth.
What Gets Distilled?
If you think about it, the “liquid” that goes into the first still (in Scotch whisky production, the wash still) isn’t a pure liquid. It has dead yeast in it, and lots of other things, including leftover undistilled liquids from previous passes through the wash still. There are unconsumed enzymes from the mashing process, malted barley solids (or in general whisk(e)y terms, grain solids), and the latter contains every kind of biological chemical compound from proteins to amino acids to fats to DNA to complex carbohydrates to trace minerals absorbed from the soil into the plant when it grew.
Then you cook that mixture to boil/extract the alcohol and whatever comes along for the ride. That’s distillation, and it’s not nearly as simple as “extract pure alcohol” — chemical analysis of single-malt Scotch whisky has identified over 600 chemicals in the distillate! That’s a good thing, too, because pure Ethanol has no flavor to speak of…what’s brilliant is that many chemicals that we associate with various smells or tastes are alcohol-soluble. Good stuff comes along for the ride, and gets refined during aging.
The spirit still will further concentrate the esters and other chemicals which are the source of the pleasant flavors, smells and textures of whisk(e)y.
So: What Did I Learn?
I was privileged to participate in a side-by-side tasting of two identical unaged California Bourbon whiskeys made with identical ingredients in identical proportions. The only difference was that each recipe used a different kind of yeast. One of the Bourbons was noticeably smoother in texture, almost buttery, with a “flatter” flavor profile. The other was much “sharper” and had (for lack of a better term) a “watery” texture, at least compared to the first one. The two samples were at the same ABV, which was over 60%, and they were roughly equivalent in that department. Both were clearly corn-based because that came out in the smell of the whiskey.
The lesson was that yeast has a heck of a lot of influence on the final product. I now have a much higher appreciation of yeast’s “unsung” contributions to the flavor of whisk(e)y.