Does yeast have an impact on flavor?

[p_elliott]

Distilleries keep samples of their yeast in several places around the world so it can't be destroyed. That's how important it is to them. One master distiller was quoted as saying if you control the yeast (meaning at that time the liquid yeast) you control the distillery.

Edited March 14, 2013 by p_elliott

[MyOldKyDram]

What a very Duneish thing to say.

The Yeast must flow.

[Yeti]

Every component matters, so of course the yeast does. Bruichladdich, and to a lesser extent Arran, are doing a lot of exciting things with different barleys from local farms in Scotland. Would they bother with that if all barley was the same? Or would there be whisky aged in countless varieties of casks (new, refill, sherry, PX, rum, cognac, hogshead, butt, puncheon, quarter cask, etc. etc. etc.) if there wasn't variation and uniqueness to be found and exploited? It is probably true that there's less focus (or even no focus) on yeast as part of scotch whisky culture because the recipes and yeasts were standardized centuries ago and nobody has deviated, but I'm inclined to believe that if you used some drastically different yeast in a bottle of Balvenie Doublewood, there would be more people than not who notice.

Edited March 14, 2013 by Yeti

[Wryguy]

What a very Duneish thing to say.

The Yeast must flow.

My high school self would have had a field day with that one.

[Josh]

Every component matters, so of course the yeast does. Bruichladdich, and to a lesser extent Arran, are doing a lot of exciting things with different barleys from local farms in Scotland. Would they bother with that if all barley was the same? Or would there be whisky aged in countless varieties of casks (new, refill, sherry, PX, rum, cognac, hogshead, butt, puncheon, quarter cask, etc. etc. etc.) if there wasn't variation and uniqueness to be found and exploited? It is probably true that there's less focus (or even no focus) on yeast as part of scotch whisky culture because the recipes and yeasts were standardized centuries ago and nobody has deviated, but I'm inclined to believe that if you used some drastically different yeast in a bottle of Balvenie Doublewood, there would be more people than not who notice.

It's funny you would mention Bruichladdich's barley experimentation, because the that's how the whole issue of yeast popped up. I said I was skeptical of the impact of barley variety on the finished product and I said that I thought yeast had a bigger impact on the taste of the final product than barley strain and everybody jumped in to tell me how very wrong I was. I stand by that, but since I haven't tasted any Bruichladdich product ever, I'm not in a good position to judge.

Anyway, I think the idea of a Scottish distiller trying a different yeast strain is an excellent one. Let's hope somebody in that business is reading this!

Edited March 14, 2013 by Josh

[callmeox]

The higher the proof off of the still, the lower the impact of the mash on the distillate.

Yeast may not matter with malts, but is sure does on bourbon.

[Beer&Bourbon]

The higher the proof off of the still, the lower the impact of the mash on the distillate.

This is along the lines of what I was thinking. Yeast certainly makes a difference in the beer. There are a bunch of microbreweries and home-brewers that could give you evidence of the difference between the chosen yeast strain. I'm certain the same is true with bread yeast (but I have no personal experience with this). That said, do those differences translate into the distillate?

There is very little difference in vodka regardless of what went into it originally. The fermentables used vary widely and I presume yeast strain matters very little - you just want something that will convert the most sugar to alcohol. Since bourbon comes off at a much lower proof other factors before distillation matter much more. If they want to argue that barley has more impact, I'd ask them to prove it (since that's what they've essentially asked you). What compounds make it through the distillation process that are different between different strains of barley? I'm not sure how far they'll get down that field, but we know that different yeast strains can tolerate different levels of alcohol and grow optimally at a variety of temperatures. These traits suggest various evolutionary pressure that has altered their genome. I imagine the enzyme repertoire is different between different saccromyces species, but you'd have to search more for that information.

With all of that said, the 4R SB tasting that a number of SB folks participated in last year saw major differences with the same mash bill among different yeast strains. I think to more definitely test your question though, you'd want to get 5-10 bottles of the same mashbill, same yeast strain to determine the influence of the barrel. You could then compare between yeast strains with some level of confidence that the differences you were noting were due to yeast strain (not barrel differences). I think you won't be able to answer this definitively with just tasting though because of the number of uncontrolled variables in your experiment (numerous barrel variables, warehouse variables, temperature variables, age, proof, grain variables, accidental variables - differences in tanking, bottling, lines used, aeration time, UV exposure on a shelf, and on and on).

[AaronWF]

Single malt is just that: 100% malted barley. From what I understand, all but two Scottish distilleries buy their malt from only a few malting houses, the exceptions being Springbank, which floor malts all of their own barley, and Kilchoman (I think?) which does some of their own malting, but not all.

So, the fact that each distillery is essentially using the same base of ingredient might mean that they all use the same yeast that has already been discovered to ferment the malt most efficiently. If you can't tell, I'm talking out of my ass here, but I've been forced to reach my own mostly-chemisterially-ignorant conclusions on this subject thus far.

Now, when I think of sourdough, I think of yeast, and although I understand that sour mash means something a little different, it still makes sense to me that yeast would play a predominant role. The more variations of grain used in bourbon mash as compared to 100% malt could mean that there is not one yeast that is demonstrably more efficient than others for use in fermenting, hence the focus in the bourbon industry on the taste properties of yeast.

I have tasted single barrels of all the FR recipes, and while I have experienced a fairly wide variety of profiles within the same mash/yeast combination (owing, I suppose, to the mysterious nature of spirit interaction with wood as well as barrel placement), I have also become familiar with the kind of profile I can expect from an individual yeast. It may not make as big a difference as barrel placement, but I'm absolutely convinced yeast plays a big factor in the taste of bourbon.

[Rarnold]

Upon catabolism of wort components (sugars, nitrogenous compounds, and sulphur compounds) to essential growth metabolites, Saccharmoyces cerevisiae will produce and excrete a variety of secondary metabolites that are detectable organoleptically.

These secondary metabolites (esters, fatty acids, alochols, vicinal diketones, organic acids, and sulphur compounds) are regulated by the expression and catalytic properties of enzymes organized into complexes. These enzymes themselves are regulated, at the most basic level, by gene expression.

Whether or not the genes required to produce a secondary metabolite (be it the end product or an intermediate) are expressed is certainly influenced by other factors aside from yeast strain type, such as mash composition, fermentation temperature, and chemical communication of the yeast with other microorganisms in the fermentation (ie quorum sensing).

However, there is no doubt that the strain type has a significant role in which genes are expressed (DNA -> RNA -> protein). In fact, one group of genes with the highest expression variability among S. cerevisiae strains are those whose transcription is relevant for fermentation progress. For example, ARO9 and ARO10 genes that code for proteins involved in the metabolism of aromatic amino acids and production of fusel oils via the Ehrlich pathway show very high expression variability among strains [Carreto et. al. Expression variability of co-regulated genes differentiates Saccharomyces cerevisiae strains. BMC Genomics, 2011].

Whether or not these secondary metabolites carry over through distillation/maturation and make an impact on the final product has never been, to my knowledge, scientifically documented. But, from experience, I believe that they do.

Rob Arnold

MSc Biochemistry

[Yeti]

I think the Bruichladdich Ãœber Provenance series - http://www.bruichladdich.com/whisky-shop/classic-whisky/uber-provenance - is a very cool product line both in theory and practice. The Bere Barley 2006 is probably my favorite >10 years old single malt, and can "hang and bang*" with whiskies three times its age and twice its cost. Extremely good whisky.

Sorry for the thread drift toward barley and scotch, back to yeast and bourbon!

* ©Hulk Hogan, 1985

[squire]

All the details matter, how often have we heard about a retiring Master Distiller instructing his successor not to change anything.

[SFS]

Upon catabolism of wort components (sugars, nitrogenous compounds, and sulphur compounds) to essential growth metabolites, Saccharmoyces cerevisiae will produce and excrete a variety of secondary metabolites that are detectable organoleptically.

These secondary metabolites (esters, fatty acids, alochols, vicinal diketones, organic acids, and sulphur compounds) are regulated by the expression and catalytic properties of enzymes organized into complexes. These enzymes themselves are regulated, at the most basic level, by gene expression.

Whether or not the genes required to produce a secondary metabolite (be it the end product or an intermediate) are expressed is certainly influenced by other factors aside from yeast strain type, such as mash composition, fermentation temperature, and chemical communication of the yeast with other microorganisms in the fermentation (ie quorum sensing).

However, there is no doubt that the strain type has a significant role in which genes are expressed (DNA -> RNA -> protein). In fact, one group of genes with the highest expression variability among S. cerevisiae strains are those whose transcription is relevant for fermentation progress. For example, ARO9 and ARO10 genes that code for proteins involved in the metabolism of aromatic amino acids and production of fusel oils via the Ehrlich pathway show very high expression variability among strains [Carreto et. al. Expression variability of co-regulated genes differentiates Saccharomyces cerevisiae strains. BMC Genomics, 2011].

Whether or not these secondary metabolites carry over through distillation/maturation and make an impact on the final product has never been, to my knowledge, scientifically documented. But, from experience, I believe that they do.

Rob Arnold

MSc Biochemistry

[HighHorse]

Upon catabolism of wort components (sugars, nitrogenous compounds, and sulphur compounds) to essential growth metabolites, Saccharmoyces cerevisiae will produce and excrete a variety of secondary metabolites that are detectable organoleptically.

These secondary metabolites (esters, fatty acids, alochols, vicinal diketones, organic acids, and sulphur compounds) are regulated by the expression and catalytic properties of enzymes organized into complexes. These enzymes themselves are regulated, at the most basic level, by gene expression.

Whether or not the genes required to produce a secondary metabolite (be it the end product or an intermediate) are expressed is certainly influenced by other factors aside from yeast strain type, such as mash composition, fermentation temperature, and chemical communication of the yeast with other microorganisms in the fermentation (ie quorum sensing).

However, there is no doubt that the strain type has a significant role in which genes are expressed (DNA -> RNA -> protein). In fact, one group of genes with the highest expression variability among S. cerevisiae strains are those whose transcription is relevant for fermentation progress. For example, ARO9 and ARO10 genes that code for proteins involved in the metabolism of aromatic amino acids and production of fusel oils via the Ehrlich pathway show very high expression variability among strains [Carreto et. al. Expression variability of co-regulated genes differentiates Saccharomyces cerevisiae strains. BMC Genomics, 2011].

Whether or not these secondary metabolites carry over through distillation/maturation and make an impact on the final product has never been, to my knowledge, scientifically documented. But, from experience, I believe that they do.

Rob Arnold

MSc Biochemistry

[smokinjoe]

Upon catabolism of wort components (sugars, nitrogenous compounds, and sulphur compounds) to essential growth metabolites, Saccharmoyces cerevisiae will produce and excrete a variety of secondary metabolites that are detectable organoleptically.

These secondary metabolites (esters, fatty acids, alochols, vicinal diketones, organic acids, and sulphur compounds) are regulated by the expression and catalytic properties of enzymes organized into complexes. These enzymes themselves are regulated, at the most basic level, by gene expression.

Whether or not the genes required to produce a secondary metabolite (be it the end product or an intermediate) are expressed is certainly influenced by other factors aside from yeast strain type, such as mash composition, fermentation temperature, and chemical communication of the yeast with other microorganisms in the fermentation (ie quorum sensing).

However, there is no doubt that the strain type has a significant role in which genes are expressed (DNA -> RNA -> protein). In fact, one group of genes with the highest expression variability among S. cerevisiae strains are those whose transcription is relevant for fermentation progress. For example, ARO9 and ARO10 genes that code for proteins involved in the metabolism of aromatic amino acids and production of fusel oils via the Ehrlich pathway show very high expression variability among strains [Carreto et. al. Expression variability of co-regulated genes differentiates Saccharomyces cerevisiae strains. BMC Genomics, 2011].

Whether or not these secondary metabolites carry over through distillation/maturation and make an impact on the final product has never been, to my knowledge, scientifically documented. But, from experience, I believe that they do.

Rob Arnold

MSc Biochemistry

[sailor22]

Yeast matters, quality and character of original ingredients matters, fermentation temp matters, type of still matters. All those things added together probably account for 30 to 40% of the taste - the rest is the aging process including barrel, wood, location and ambient temp. will account for 60 to 70% of the flavors. That's what two noted master distillers have told us in recent weeks here at the local Whiskey Society events.

BTW - in the conversation with Jim Rutledge that High Horse referenced earlier Mr. Rutledge said they don't make any cuts at all for heads and tails. So that would eliminate the heads and tails cuts variable someone mentioned. Also it seems every time I ask about the corn used I'm told #2 dent is the standard used by all the major distilleries. Rutledge stressed that there are differences in the quality in that grade. Balcones, High West and probably some other micros use blue corn to get a different product.

[squire]

I'll take the word of the Masters.

[drunk]

Which recipes would you recommend I purchase to best highlight the differences between yeasts?

Trey, I didn't see anyone reply, but if you want an easy comparison, pick up a Q yeast and compare it to a standard OBSV. It's the "floral" one, but I'd call it perfume-y. It's like the IPA of the Four Roses line-up. The F yeast is the second most distinct one with grassy or minty notes.

[Trey Manthey]

Thanks! I have placed an order with Party Source for OBSF, OBSQ, and OBSV.

[DaveOfAtl]

Looking forward to your impressions.

[tmckenzie]

Yes, yeast matters. here is a kicker though. It has been my experience that not so much on rye mashbills that have no corn in them, and malt mashes. It makes the biggest difference in corn based whiskies. And the same yeast will give 2 different flavor profiles I have found, based on what type of yeast mash it is grown in. Sweet or soured yeast mashes. Sour yeast mashes, soured by lacto produce fruit profiles, when the same yeast grown sweet, may not be fruity Amazing how yeast react to different environments. They have to adapt and when they do, they make different flavors.

[squire]

Good point about yeast adaption Tom. I remember the story of when Seagrams owned the LDI plant they tried to reproduce on of their more popular whiskys in a Canadian plant and discovered the specific yeast for that recipe wouldn't adapt to the colder climate there.

[benpearson]

For those who would like some sort of scientific explanation look to Rarnold's post (very well put)...or you can read a brief summary of the chemistry here. Basically different yeasts produce different congeners which in turn produce different flavors when aged.

I find it interesting that the topic of Weller/Pappy/Maker's/Bernheim hasn't come up...but that may be too complicated to digest. I don't know for sure the lineage of the different producer's yeasts.

As far as four roses goes, yes there is a difference between the 10 recipe's. I would like to think I can blind taste the difference, but I have run across barrels that have surprised me both in barrel tastings at 4R and in bottles I have picked up at various retailers. I doubt that yeast is the only variable in distillation. If memory serves me correct the practice originated in having 5 separate distilleries and a central warehouse.

As a retailer we are starting on a series, where instead of picking our favorite blindly from all the recipes we are asking for 6-8 samples of just one recipe. Picking our favorite one, and having it bottled. Sort of our way of not being biased towards a particular recipe. I've noticed a lot of people picking F yeast lately, and I feel it's mainly because it stands out as so different from what has been available in the past. I have nothing against F, but I think it's important to focus on all the recipe's not just one. We have started with OBSO and OESO, when those have mostly sold we will go on to OBSK and OESK, etc. At the end we will most likely have held back some bottles from each to taste at a special event.

[Josh]

Yes, yeast matters. here is a kicker though. It has been my experience that not so much on rye mashbills that have no corn in them, and malt mashes. It makes the biggest difference in corn based whiskies. And the same yeast will give 2 different flavor profiles I have found, based on what type of yeast mash it is grown in. Sweet or soured yeast mashes. Sour yeast mashes, soured by lacto produce fruit profiles, when the same yeast grown sweet, may not be fruity Amazing how yeast react to different environments. They have to adapt and when they do, they make different flavors.

That's very interesting, I was hoping to hear from a distiller about that. Any theories on why it doesn't make as much of a difference in rye and malt whiskeys?

[Halifax]

Thanks! I have placed an order with Party Source for OBSF, OBSQ, and OBSV.

Afterwards, I would also suggest OESQ, OESK, OESO and OESF. These are among my favorites. Especially the OESK. Enjoy!

[ethangsmith]

If yeast isn't important, than why do distilleries have yeast banks and yeast labs? Why do they cultivate yeast and create lactic sours? If the yeast doesn't have a flavoring role in the final product, it shouldn't matter....

FWIW- Dick Stoll told me that Michter's went from Beam yeast after Everett Beam left to a pre-packaged yeast. He said since they were all so familiar with the process, the change in yeast didn't affect the flavor all that much. They also took the pre-packed stuff and continued to cultivate their own lactic sour off of it as needed for consistency. This leads me again to believe that yeast does at least factor into flavor at least a little bit. I don't think it has a big impact, but in my opinion this is where some of the subtle flavors come from (Nuttiness, citrus, leather, brashness versus mellowness, etc.).