Yeasterday

I would think that the only good way to learn which flavours are brought into a whisk(e)y by the choice of yeast used would be a systematic study of whiskies made with all other controllable variables being contolled. There can be no control of the specific barrels/casks used, but there can be control of the quantities, sources, and processing of the grains used, the source of the water used, the specific stills used, and the industrial processes employed in the production processes.

Four Roses' 10 separate bourbons are one of the few existing examples which can give give insight into the differences resulting from yeast flavour effects. Multiple batches of the 5 different Four Roses bourbons using 5 separate yeasts, but the same mashbill, have been compared by the Four Roses personnel, and described for public reference. If you sample the various Four Roses formulae, you will find that these various yeasts clearly yield different-tasting whiskies.

I strongly agree with the observation, reported by Charles "Chuck" Cowdery to have been made to him by various US distillers, that 50% of the flavours of a (US style) whiskey comes from the wood, 25% from the grains, and 25% from the yeast.

Every sugar molecule is converted to alcohol through a yeast molecule. Yeast is pretty dram important.

@Victor As always, I am stuned by the way you always bring me to broaden my view. I will go back to those reviews of Four Roses' 10. I was not giving them a lot of attention because there are not available near me, but now you pointed out how good they could be for my education as a whisky enthusuast. Sometime I may sound foolish or naive, but being a teacher I learn that the best way to learn and improve your knowledge is to ask questions, test your hypothesis and let your curiosity guides you. But I will confess that, at the end, the best discovery I do are in my glass. So again, Cheers!

@Benancio "Dram important", I am crying over that one! But it is well deserved! But if I stops laughing for a moment (Believe me it's hard!), I will ask a question that will add to my post and that I had in mind. Don't you taste the yeast itself in Bourbons? I think I do and it is very nice and I tend to see the flavors that come with it as the products of that yeast. Yet the yeast itself, I noticed it only in Bourbons and not all of them. When something close to yeast flavor comes into a scotch, I would judge it a flaw because... well it doesn't work. The difference initiate my rumination althoug a discussion about yeast must be a spiritual one!

Forty Creek's one-time expression Heart of Gold (sadly sold out but available to taste at my home for those interested) was, I believe, created with yeast in mind. From what I understand the rye was fermented with a strain of yeast normally used in rye. I admit I am not the FC expert in this group, but I do believe that expression is unique.

Interesting question.

In the past you would have heard the Scots banging on about the water and the barley. Then there was a period of time where peat was the subject of interest. Of late the focus has shifted to wood management: quality and types of the barrels/casks used.

Perhaps the influence of yeast strains may be the next big thing?

@sengjc, all they can say about the yeast is something like, "We've got this great yeast" or "Ours is the best yeast"...because it is so hard to document and define which of the flavour elements come from the yeast.

I would like to see much more conversation about yeast, because it so important. I don't think that we will see this much-expanded yeast conversation because it is such a subtle subject about which it is difficult for commercial interests to make strong self-aggrandising claims.

The influence of yeast in whisky is huge, but it is enigmatic.

@Nozinan, interesting, I was under the impression that John Hall used "wine" yeast(s) for his fermentation...some rye producers make use of enzymes, and their whisky is delicious. Alberta Distillers use enzymes for their rye; they (arguably) are the top rye whisky producer on this planet.

@paddockjudge

Sorry, that's the problem of typing on an iPAD. I meant to say he uses yeasts commonly used for wine. I wonder what yeast was used for the "Amrut Amarone".... ;)

yeast type/strain/quantity, barley type/location/quality, water type/minerals, grist composition , wash backs composition/volume/history, fermentation process length, shape wash & spirit still/lyne arm/purifier/condenser/worm tubs, direct/indirect fired, distillation temperature, selection fore shots/heart/feints, cask shape/wood/charring/history, transportation, maturation location/position/duration, colouring, filtration, vatting techniques,... So many factors that are supposed to influence the flavours and composition of the whisky. I find it hard to pin it down to simply a variation of the type of yeast that was used. But an interesting conclusion non the less.

One thing I learned on Islay was that they reduced the amount of yeast that they used during the fermentation. Traditionally they would add a lot more yeast as they believed that it would speed up the process. Only a small amount is needed to start the process, any additional yeast is now considered useless.