How distillers use yeast to influence character in spirits

[flahute]

Who's ready to nerd out again?

Some really great info here that covers more than just bourbon. @WhiskeyBlender I'd love to hear your thoughts on this.

Pay special attention to the influence of wild yeast and what that meant for Leopold when they moved.

 

https://daily.sevenfifty.com/how-distillers-use-yeast-to-influence-character-in-spirits/

[lcpfratn]

Thanks for sharing this article, Steve!

[Old Hippie]

Excellent article Guru

I believe that the yeast strain is proprietary for most of the larger bourbon distillers. As I understand it some even have a DNA map of their particular strain and check it annually.  Back in the old days the Distiller also had the title of yeast propagator. They  would set several solutions out on the porch and use the one they liked. 

[Richnimrod]

3 hours ago, Old Hippie said:

Excellent article Guru

I believe that the yeast strain is proprietary for most of the larger bourbon distillers. As I understand it some even have a DNA map of their particular strain and check it annually.  Back in the old days the Distiller also had the title of yeast propagator. They  would set several solutions out on the porch and use the one they liked. 

Those 'old days' were the VERY old days!     

Not certain when the last time this occurred for any big distillery; other than in a very scientific way, and/or by some of the recent startups that have some size and capital (See Chuck's article in the latest BCR about Firestone & Robertson).  

[Old Hippie]

On 7/1/2019 at 12:45 PM, Richnimrod said:

Those 'old days' were the VERY old days!     

Not certain when the last time this occurred for any big distillery; other than in a very scientific way, and/or by some of the recent startups that have some size and capital (See Chuck's article in the latest BCR about Firestone & Robertson).  

Yes sir - we're talking 1800's and before

[WhiskeyBlender]

On 6/30/2019 at 7:05 PM, flahute said:

Who's ready to nerd out again?

Some really great info here that covers more than just bourbon. @WhiskeyBlender I'd love to hear your thoughts on this.

Pay special attention to the influence of wild yeast and what that meant for Leopold when they moved.

 

https://daily.sevenfifty.com/how-distillers-use-yeast-to-influence-character-in-spirits/

Wow, what a fantastically nerdy topic, and a big one too boot, @flahute! You might even call this the "politics" of spontaneous fermentation vs. inoculated fermentation with cultured yeast strains, because in the industry it can be such a divisive topic.

 

There are so many factors that go into a decision of whether or not to use spontaneous fermentation with native, ambient yeasts. As you know, I originally came from the brandy world before moving into whiskey production, so I'm going to draw some of the philosophy behind that kind of production into the mix as well. I personally think there is room for both methods, depending upon what the distiller is trying to achieve, but there are certainly some caveats that need to be considered. I have enjoyed some matured spirits that were the products of spontaneous fermentation that have been beautiful and very complex, and some that have been rot-gut swill, so it all depends upon how carefully it is done. 

 

Thus, some of the PROS for using native yeasts without using any cultured yeasts for fermentation would be: 1.) to produce more complex, unique flavors than what one can achieve just through the use of cultured yeasts, 2.) this kind of approach can be great if one is going to lay down a spirit for long term maturation (i.e. 20 to 50 years for a high quality brandy), as the various esters, acids, aldehydes, etc., when combined and transformed in the presence of oxygen in the barrel over time, can eventually create a spirit that is spectacular and has great length, depth, finesse, complexity, etc., and 3.) if it is part of the distiller's production philosophy to showcase the local terroir, this is a great element to revealing a true "taste of place." 

 

The list of CONS, on the other hand, can be quite overwhelming. Probably the #1 factor that a distiller has to take in to consideration is whether or not consistency is of great importance. Thus, if you have a particularly good spontaneous fermentation, can it be replicated? Are you making a product that must be consistent from batch to batch, or is it part of your house style/philosophy to have some variation between them? This is not only a stylistic choice, but can be a real dilemma that can have huge financial and commercial implications if things do not work out as planned with the wild yeasts. 

 

Consideration #2.) for total, clean alcoholic fermentation, as we all know, it is vital to have the yeast species Saccharomyces cerevisiae. In addition to the wild strains, there will often be some S. cerevisiae hanging around on grape skins or other fermentable substrates. But what if there are not enough to help combat the effects of spoilage yeasts or other spoilage organisms like acetobacter, lactobacillus, etc.?  The problems can be two-fold here: since wild yeasts are usually not able to stand up to high alcohol, it is not uncommon to get stuck fermentations with lots of residual sugars. These yeasts tend to die somewhere between 1 to 5% ABV. And since it takes wild yeasts a long to time colonize and really get going, this sets up the perfect environment for the spoilage organisms to infect the ferment so that off notes such as VA (volatile acidity) or acrolein can develop. Also, without using an S. cerevisiae innoculation, there is also the risk of oxygen spoilage, etc.. There is also the risk of various types of sulfur notes developing, which can develop through weak yeasts, etc. Granted, there are ways to deal with this and get the best of both worlds, such as to inoculate with cultured yeasts once the wild yeasts have run their course, but given the fickle nature of spontaneous fermentation, this may or may not work. 

 

Consideration #3: fermentations using solely ambient, native yeasts can be very long. For example, for Calvados production in Normandy, France, where conditions are damp and cool, it is not unusual for wild yeast fermentations to begin in the fall and finish in the spring, going on about 2 to 6 months. I've even heard of fermentations going on for 2 years! 

 

While this isn't a definitive list of pros and cons, I hope at least it gets the conversation going. 

 

I look forward to hearing thoughts, opinions, etc. on the subject. Many thanks @flahute for getting such a fun topic rolling! 

 

Cheers,

Nancy

 

 

 

 

Edited July 2, 2019 by WhiskeyBlender

[Oli77]

This is great and very complicated, it's a miracle Master Distillers are able to maintain consistency across batches and years.

 

Do we know if the different yeast strains produce different esters, alcohol, phenols, etc... to impart different tastes to the juice prior to distilling?

 

Or does the substrate the yeast is feeding on alter the flavors of the alcohols produced?

 

Or is it a combination of both, where what the yeast is feeding on, together with how that strain transforms the sugar to alcohol becomes important? 

 

Ultimately, the source of sugar, the temperature, the terroir, the other wild factors, all get together with a particular  strain of yeast to make magic.  

 

Edited July 3, 2019 by Oli77

[PaulO]

I used to home brew beer a lot, before I had a child.  I was always careful in my sanitizing procedures.  I had a great time experimenting with yeast strains.  My analogy is - different yeast strains are as breeds of dogs.  It's the same species, but doesn't look or act the same.

Granted, distilling and aging makes things way more complicated.

I've wondered, how about a wheat mash bill bourbon fermented with Bavarian wheat beer yeast?

[flahute]

On 7/2/2019 at 6:31 PM, Oli77 said:

Do we know if the different yeast strains produce different esters, alcohol, phenols, etc... to impart different tastes to the juice prior to distilling?

Yes, they do. This is why yeast is so important.

[flahute]

On 7/2/2019 at 4:28 PM, WhiskeyBlender said:

I look forward to hearing thoughts, opinions, etc. on the subject. 

I have to admit I was surprised that the big distilleries actually admit to the possibility of this and that it can influence the flavor even though they can't totally quantify it.

Does this help explain (among other obvious things such as different still, etc.) why post fire Heaven Hill distillate is different from pre fire? (For those who don't know, the distillery was in Bardstown before it burned and they distill in Louisville.)

I'm familiar with the Four Roses mutant yeast story which resulted in the amazing 16 and 17yr OBSV barrels but that was a one off event.

This will be my next topic of discussion when I see Pat at Wilderness Trail again.

[Oli77]

Right, Pat at Wilderness Trail got his degree at UK studying yeast. Likely has something to do with the quality of their product for sure, Hummmm.