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The role of yeast in the bourbon making process


jbutler
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Just an interesting topic for discussion, as I possess little other than anecdotal evidence regarding the subject. I once made a batch of beer, divided it in three parts and pitched a different yeast strain into each. The result was three quite different brews that happened to be the same color. 

Living in the heart of wine country, I've spoken with many people employed in that industry, and they universally downplay the role of yeast in the flavor of the final product. I suppose that it's more romantic to believe that the flavor originates from the fruit and some French wood rather than unglamorous little critters that eat, shit, then die in droves. Note that I haven't actually spoken to a winemaker, so what we likely have there is a lack of understanding on the part of some of the downstream workers.


So the big question is how much of a role does the yeast play in the final flavor profile of bourbon? I'm particularly interested in empirical data, if anyone has it on hand or knows where to find it. Your thoughts?

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Jim this is a very good question. From a beer standpoint, the influence of yeast is significant as you suggested. I know this in many ways, e.g. I don't like most "Belgian" IPAs and stouts. It's because I can taste that figgy-cinnamon yeast taste common in Belgian ales and I don't like it. If yeast didn't matter, I wouldn't notice such things. Most brewers are in agreement on this I believe.

 

In terms of whether flavor is affected when you distill a fermented corn mash, I believe the answer is similar. It stands to reason if your corn-based beers will taste different with different yeasts, that comes over in the distillate. For example, if you can taste apple esters in, say Laird's applejack, why wouldn't you taste esters in a corn beer produced by using a yeast with a prolonged slow ferment at high temperature? Stands to reason. Also, see e.g. this opinion from a supplier of distilling equipment, he says yeast has a "major impact" on whiskey flavour.

 

http://www.clawhammersupply.com/blogs/moonshine-still-blog/12263809-making-moonshine-fermentation-and-yeast

 

In one of the sources I read in my recent look at 19th century literature on whiskey, a writer said, when most bourbon was produced in the old sour mash way (no added yeast), each region's whiskey tasted different because the microflora were different. (He didn't use that word but that's what he meant). If all wild yeast was the same, then this kind of statement doesn't make sense.

 

As for the winemakers' view, could it be they are all using the same or a similar strain of single cell yeast commercially supplied? If so that might explain it. E.g. I've read that for commercial lager, only two strains of yeast are used worldwide, one comes from Carlsberg and I can't recall the other. So this is why many lagers tend to taste similar today. But ales and porters tend to be much more diverse in terms of yeasts used.

 

Gary

Edited by Gillman
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20 minutes ago, Gillman said:

I've read that for commercial lager, only two strains of yeast are used worldwide, one comes from Carlsberg and I can't recall the other.

Saccharomyces Uvarum, which one would think would be used in wine as well, but apparently S. Ellipsoidium is the main actor there.

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Yeasts can produce all sorts of other flavor by products besides the main ones that are ethanol and CO2.  Lager yeasts were selected to produce the least amount of other flavors.  Also, fermenting at a lower temperature helps but goes more slowly.  The same yeast can give different results based on temperature.  

I'm a fan of Hefewiezen beer, but I know it's not for everyone.  I've wondered how that yeast strain would do for a wheated bourbon mash bill?

I think the different strains of yeast are like different breeds of dogs.  It can be the same species of organism, but be very differnt in some ways.

Back when I did a lot of brewing, I had a lot of fun with the different yeast strains.  One company had these mylar pouches with a little blatter inside to break.

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time to get someone from Four Roses in here to talk about yeast strains.

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1 hour ago, PaulO said:

Yeasts can produce all sorts of other flavor by products besides the main ones that are ethanol and CO2.  Lager yeasts were selected to produce the least amount of other flavors.  Also, fermenting at a lower temperature helps but goes more slowly.  The same yeast can give different results based on temperature.  

I'm a fan of Hefewiezen beer, but I know it's not for everyone.  I've wondered how that yeast strain would do for a wheated bourbon mash bill?

I think the different strains of yeast are like different breeds of dogs.  It can be the same species of organism, but be very differnt in some ways.

Back when I did a lot of brewing, I had a lot of fun with the different yeast strains.  One company had these mylar pouches with a little blatter inside to break.

 

2 hours ago, Gillman said:

In terms of whether flavor is affected when you distill a fermented corn mash, I believe the answer is similar. It stands to reason if your corn-based beers will taste different with different yeasts, that comes over in the distillate. For example, if you can taste apple esters in, say Laird's applejack, why wouldn't you taste esters in a corn beer produced by using a yeast with a prolonged slow ferment at high temperature? Stands to reason. Also, see e.g. this opinion from a supplier of distilling equipment, he says yeast has a "major impact" on whiskey flavour.

 

Different varieties of yeast will produce different compounds and therefore different flavors in beer, but I think it's also important to consider the volatility (boiling point) of the different compounds. I believe those compounds (congeners) are going to evaporate at different points during distillation, so that even if they're created during fermentation, is doesn't necessarily mean they pass through to the final product in detectable amounts, as they may be mostly in the heads, tails, or be left in the backset. For example, good apple flavor in a cider doesn't always translate to good apple flavor in the resulting brandy.

 

Full disclosure: I don't have an extensive science background, so my info comes from distillation articles I've read in addition to what I've experienced during some distillation experiments.

Edited by Kpiz
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Every drop of alcohol has been created by yeast cells. Thinking of it that way it would seem the contribution to flavor is huge, and it is.

 

Having said that, my impression is the distillers yeast utilized today all have a consistent enough character the flavor variation seems minimal.

 

I suspect much of the current distillers yeast is sourced and quite a bit of it would be a dried Red Star yeast. Consistent, predictable quality - no muss no fuss.

 

If one distiller was using a beer lager yeast; another was using Hefeweizen yeast; another was using Montrachet wine yeast; and another was using a Flor Sherry yeast I'm pretty sure based on my own trials the variation could be measured and tasted in the finished product.

 

The problem of a 'sour house' yeast wreaking havoc within brewery, winery, or distillery keeps fermentation diligence high, as it should. Once set in that acetobacter or other form of nasty uncontrolled undesirable yeast activity is quite difficult to oust from a system.

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Interesting that you brought up the subject. I was reading an article in the latest issue of Whisky magazine, August 2016, called Dr. Livermore Master Blender. In the article Don Livermore Master blender at Hiram Walker in Canada studied the subject. He said that the various flavor chemicals called congeners in new and maturing spirits come for the grain, specifically the lignin that holds the grain together. However his research shows the greatest concentration of the flavor congeners comes from the yeast, and not the grain.

 

He also stated that yeast, a living organism, responds to how it is treated, so the distiller can influence the flavor by raising the temperature of the fermenting mash, lower the oxygen, and according to him, even stirring the mash can change the flavor profile. It is a pretty interesting article.

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3 hours ago, whiskey buyer said:

He also stated that yeast, a living organism, responds to how it is treated, so the distiller can influence the flavor by raising the temperature of the fermenting mash, lower the oxygen, and according to him, even stirring the mash can change the flavor profile. It is a pretty interesting article.

Lowering the temperature can work as well.

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When I was becoming interested in whiskey after our first trip to the Bourbon Trail I posed that question to the head of the biotechnology program at the school I was attending. The distillery tours emphasized the role of yeast  (especially 4R) in the flavor of whiskey but I was skeptical. He assured me that yeasts play a big role in the flavor of any alcoholic beverage. Since then I've done a lot of whiskey and beer sampling and I'm convinced they're right. Knowing the yeast strain used in a beer enables one to predict flavor characteristics. The Belgian and hefeweizen examples Gary and Paul provided are classic examples. I'm also convinced it plays a big role in whiskey as evidenced by the difference in house styles. Using the same ingredients and similar mashbills they manage to create distinctly different whiskies and I believe one of the reasons for the difference is the difference in yeasts. 

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I know nothing about yeast, but I do know how different the different 4R mash bills taste with different yeasts. I would also assume that the different funky tastes in Jim beam, wild turkey and buffalo trace products are all by products of their proprietary yeasts.

Sent from my SPH-L720 using Tapatalk

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11 hours ago, Kpiz said:

 

 

Different varieties of yeast will produce different compounds and therefore different flavors in beer, but I think it's also important to consider the volatility (boiling point) of the different compounds. I believe those compounds (congeners) are going to evaporate at different points during distillation, so that even if they're created during fermentation, is doesn't necessarily mean they pass through to the final product in detectable amounts, as they may be mostly in the heads, tails, or be left in the backset. For example, good apple flavor in a cider doesn't always translate to good apple flavor in the resulting brandy.

 

Full disclosure: I don't have an extensive science background, so my info comes from distillation articles I've read in addition to what I've experienced during some distillation experiments.

 

 

Very true but esters must come over as I've tasted countless fruit spirits which taste of the fruit in question (distilled only, no flavour added). A beet spirit from a local craft distiller, Toronto Distillery, is a good example. It has a strong odour and taste of beets. The white alcohols of Alsace-Lorraine, another example.

 

Gary

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Given the 4R example, it seems that at least some flavors from the different yeast strains can make it rhrough the distillation.  

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