View Full Version : Sweet Mash -vs- Sour Mash

10-05-2003, 10:05
While doing a little research for making the "how bourbon is made" part of my site I came across something I honestly never heard of. Well, perhaps I did and just paid it no mind. Anyways, I did some searching around on here as well as the net and found out a bit about it. I knew with the Sour Mash method it involved leaving some culture or mash from a previous batch to be added to the next batch, similiar to making sourdough bread.

Now in the Sweet Mash process new yeast is processed quickly over a few days.

I 'think' I remember also reading somewhere that the sour mash process results in a lower Ph whereas the sweet mash process usually has a higher resulting Ph but it is loweded with the addition of an acid. Anyways, my questions is this: Do any distilleries use the sweet mash process? I've read on the internet and even on Buffalo Trace's webstie that they di indeed use this process. While reading posts on here I have read no current US distilleries use this process. Anyone have any information to share about this? I see that Chuck has previously written about this process and did make mention that no distilleries use this process. Chuck, do you know if there has been a change in practice over there or do they possibly use both practices for different products or something? Thanks for any input guys...

10-05-2003, 11:07
I've read on the internet and even on Buffalo Trace's website that they do indeed use this process [Sweet Mash].

Are you sure!? Their PR video thing specifically says it's a sour mash process:

"The corn is added to mashing water which has been heated to its boiling point. As the mixture cooks, rye is added. After the mixture cools, the malted barley is added and now the mixture becomes a sweet mash. When the mash temperature reaches 64F, yeast with a small amount of previously fermented mash or sour mash are added. The sugary enzymes of the malted barely feed the yeast to produce alcohol and carbon dioxide."

10-05-2003, 11:23
Yep (http://www.buffalotrace.com/product_dist_m.html ). Says so here, though I am wondering if they just aren't clear about the whole process in general.

Like I said, the thing that made me wonder about all this is another site somewhere stated that BT was the only distillery to still use the sweet mash method. But once I saw Chuck say otherwise in a previous post from some time ago it made me wonder... I doubt he is wrong, this other site didn't sem very reliable anyways. I just want to know if I should correct my site now haha.

10-05-2003, 11:46
Thanks to Dr Crow for sour mash. What I have read states that the Sour Mash process results in a superior product. Tdelling says it is a QC issue only. The Regans say Jim Beam uses 42% backset. It seems to me they are " Wearing out the water" at that point.

The thing I want to find out is where do distilleries get the backset after a shutdown, Or is the first run sweet mash and then it goes to sour mash. Sam Cecil specifically states that at the Old TWSamuels plant they had a contract with Hueblin for spent mash after a shutdown.

All that I have read on this which may amount to " Not Much" I have seen no praise for sweet mash. It's like Brick warehouses , only the ones with them and the doers of sweetmash, claim it's better.

10-05-2003, 11:58
The thing I want to find out is where do distilleries get the backset after a shutdown, Or is the first run sweet mash and then it goes to sour mash.

I believe that some actually get backset from other distilleries. Makers Mark, from what I have heard, gets theirs from Heaven Hill.

10-05-2003, 12:14
That's the obvious answer, Mark. I plan to ask around to see what they will admit to. I would think this to be a secret on the order of the yeast thing.
It would seem that there are more similiarities than differences at this point. But here we go........Bump in the road....... With only Buffalo Trace, HH , and Maker's running Wheat, do they schedule so that someone has it going all the time, I can't imagine Maker's using a backset with rye, And I can't imagine that someone is running wheat every week of the year...........Busted...... I guess they could freeze a big chunk of it

10-05-2003, 12:28

I don't think you can freeze it...Like Chuck's logo says...Whiskey don't keep...Well I spect that "backset don't keep" either http://www.straightbourbon.com/forums/images/graemlins/grin.gif...LMAO http://www.straightbourbon.com/forums/images/graemlins/grin.gif

http://www.straightbourbon.com/forums/images/graemlins/grin.gif http://www.straightbourbon.com/forums/images/graemlins/grin.gif Bettye Jo http://www.straightbourbon.com/forums/images/graemlins/grin.gif http://www.straightbourbon.com/forums/images/graemlins/grin.gif

10-05-2003, 12:35
I was wondering about freezing it as well for a bit haha. I know yeast cells from a pure culture are kept under refrigeration but not about some backset.

10-05-2003, 12:57
Shouldn't the yeast be dead, after exposure to 170degree plus heat? Actually I have had conversations to the contrary.

10-05-2003, 13:02
That's right Bobby. I thought the function of backset was to provide unfermented sugars to the next batch of beer, adding of course the quality of consistency through some chemical principle.


10-05-2003, 13:42
And also to lower the PH Hence the name " Sour Mash" the yeast work more efficently in a more acidic environment.

10-05-2003, 14:03
This factor (the PH you mention) may be the main one. I was just reading in Byrn's book on distillation (1875) that the unfermented sugars in spent beer can't be used again, he says they are "gummy", they won't ferment and he suggests that spent beer be used as fertilizer! Interesting that he seems to show no knowledge of what James Crow pioneered 50 years before. Then too this is a Euro-centric work which seems to not take much notice of what Kentucky was doing in distillation.. Maybe a case of (to mix metaphors) .. sour grapes? http://www.straightbourbon.com/forums/images/graemlins/smile.gif


10-05-2003, 15:37
Well, I do know that the famous Czechoslovakian pilsner, Pilsner Urqell, claims to have maintained the same continuous yeast culture for over 1300 years! First, they are European and second, they have been doing it for a very long time.


10-05-2003, 15:59
Well, I do know that the famous Czechoslovakian pilsner, Pilsner Urqell, claims to have maintained the same continuous yeast culture for over 1300 years! First, they are European and second, they have been doing it for a very long time.

Yes, but for beermaking it's a different process. In distillation, you actually boil the beer so the alcohol vapors climb your distillation tower. In beermaking, you can simply bottle your wort, then put fresh wort over the old yeast cake...keeping it vital.

10-05-2003, 16:59
Well, yes and no. Breweries have to revive their yeast about every 5 brews else it would go haywire/sour. They do this by reference to a pure culture maintained in labs (a fairly modern innovation). That, or they get new yeast (if there is a total yeast failure for some reason) from one of their brewing neighbours, a gentlemanly practice that endures in the alcohol businesses..

Czech pilsener was invented in the 1840's as a golden bottom-fermented beer. Before that beers were generally murky dark and top-fermented at ambient (warm) temperatures. So the Urquel yeast had to be new (not the brewing tradition, but the yeast). The major beer type before its invention (and historically in German lands and still in the U.K. and Belgium until recently) was ale - dark top-fermented beer which could only be made in the autumn until the spring. Cold (bottom) fermentation was perfected in the 1800's in a number of locales in Middle and Eastern Europe including Pilsen. So, before the new era of cultured yeasts working at cold temperatures assisted by mechanical chilling, beers were much more variable in flavour than the new beers such as Pilsener Urquel (and Munich lager, Danish Carlsberg, etc.). So the PIlsen industrial bottom yeast was new and was certainly helped by scientific savvy coming onstream in the mid-1800's (e.g. Pasteur in France). Very relevant to distilling. Old time distiller's yeasts likely were exotic but variable. This is why (I think) Lincoln Henderson in the current Malt Magazine insists whiskey today is overall better than back then: there is better control, in yeast anyway, and he mentions yeast as a vital flavor contributor.


10-05-2003, 18:33
Well, yes and no.

Sorry, but yes and yes. All the song and dance you posted about how beer is made doesn't change a thing about beer vs. distilled spirits. And yes, you're absolutely correct about having to correct the yeast every 5 or so batches--that's what's called mutation. You can't trust your old yeast strain after 2 or 3 batches.

The same doesn't hold for distilled spirits--the wort is BOILED before it's fractionated in a column or otherwise--you can't just decide at random to recycle the strain.

10-05-2003, 18:45
Sorry, I wasn't talking about whether beer is boiled to make spirit, of course, it is and sorry my post didn't distinguish clearly what I meant.

I meant that I doubted Pilsener Urquel maintained the same yeast culture for hundreds of years.

As for beer being boiled to enter a fractionating column, before it is boiled, I would think fresh yeast can be, and is, removed from the beer to add to the next mix of backset and fresh mash. Removed before the boil, that is.

By the way my opinions are just that. I studied (as a hobby) beer for 30 years before learning about whiskey, and I am happy to learn more anytime, where I am wrong or don't know the area.


10-05-2003, 18:47
While reading posts on here I have read no current US distilleries use this process. Anyone have any information to share about this? I see that Chuck has previously written about this process and did make mention that no distilleries use this process.

I seem to have read that no current STRAIGHT WHISKEY distilleries use a sweet mash process. I have heard that some other US (e.g. single malt or grain neutral spirit) whiskey producers may use a sweet mash process. I don't think I've seen this in writing though, so I can't say which ones might do so. http://www.straightbourbon.com/forums/images/graemlins/confused.gif

10-05-2003, 18:58
I seem to have read that no current STRAIGHT WHISKEY distilleries use a sweet mash process.

That's pretty much what started this whole controversy---Mark seems to think that BT uses a sweet mash process. Their public-relations video says it's a sour mash process, although he's 100% correct that their website cites a sweet-mash process.

10-05-2003, 19:14
I'm beginning to think more and more that they do use the sour mash process and their site just is not very clear on it after hearing others opinions on the matter. I am going to write someone over at Buffalo Trace I know and see what they say for clarification. I'll be sure to post back, probably sometime tomorrow, with the final verdict straight from their mouth haha.

10-06-2003, 03:58
Ok guys, and the final answer is:

" <font color="green"> Yes. All Bourbon (including ours) is made using the sour mash process.

Our Rain vodka is made using a sweet mash process and it maybe that we refer to our bourbon making process as sweet mash until the point where we add sour mash.

Hope that clears the mystery up.

I guess that makes sense to call it such until the time the backset is added, but it made for a confusing read on different websites haha.

10-06-2003, 06:16
I have a copy from 1818 of a pair of recipes from a woman distiller in Kentucky. On one side is a recipe for sweet mash distiller's beer, the other, a recipe for sour mash. In this recipe sour mash was a process more similar to sourdough bread. In modern times the process has changed. By the time the mash has been distilled the yeast is dead and the spent beer is used only to recreate the best environment for the yeast strain to grow in by helping to match the ph of the mash. I suspect that on a start up situation most distillers will use some other acid in their mash to get the proper ph thus making it a "sour mash". I know Chris Morris stated at L&amp;G that that is what they do for the whiskey they are distilling for Woodford Reserve.

Mike Veach

10-06-2003, 06:21
I am glad they clarified that for us. Their comments on the web site which started all of this should be better explained. They should know some of us REALLY read these things! http://www.straightbourbon.com/forums/images/graemlins/wink.gif

10-06-2003, 06:54
Mike, that is very interesting. Can you elaborate on the woman distiller's concept of sour mash? Do you mean she collected yeast from the ferment and added it to the next mash to ferment the next batch of beer before it was distilled?

If that is correct that is different from the modern understanding as you said.

I looked again in Byrn's Practical Distilling text of 1875. (This book in its reprint form was mentioned on this board about a year ago, it can be purchased from Glenn Raudins, the reprinter, at www.raudins.com (http://www.raudins.com)). The book is mainly concerned with distilling proper. But Byrn does discuss mashing, and fermentation in a number of passages. Twice when talking about French methods, he says spent wash is taken from the still and mixed (always, he says) with water. Then it is added to a mash to "cool and dilute" it. He says this is done because there are unconverted starches which still can be converted and even some sugars that (despite his statement elsewhere in the book that these are unfermentable) can be fermented to make more alcohol. He says also this process can only be used 3 -5 times successively because the spent wash becomes too acid, he actually says, "sour", and fermentation will not occur after such number of applications. This suggests he meant the distiller must ferment completely anew (no backset) after about 5 sourmashes.

A separate point he does not address is whether yeast is collected from the fermented mix of backset and mashed grain to add to the next ferment. I assume (but don't know for sure) that yeast must today be collected in this manner, as in straight brewing, to add to the next mash (whether it has backset or no and one thing is sure, that backset will have no live yeast in it).

Can a brand new yeast be prepared from a pure culture for each mash? Is that feasible given the amount of yeast needed in large scale mashing? I don't know the answer to that one but have always assumed the distillers would collect yeast from a previous mash, store it and use it for the next one until they need to refresh it for reasons earlier discussed.


10-06-2003, 07:14
Yeast is always added to the mash. Some use bag yeast, other raise their own from a culture, but they always add yeast. The spent beer is used only to create the best conditions for that yeast to grow. The yeast in the spent beer is dead by the time it is added to the mash. This means that if yeast was not added, you would be depending upon wild yeast from the air for your fermentation and there is no telling what type of product you would end up with in your beer.

I would also find it hard to believe that one distiller would use spent beer from another distillery to sour their mash because of the different yeast strains and more importantly different grains or amount of grains could change the flavor of the product. Someone mentioned Maker's Mark using Heavan Hill spent beer for their start up, yet until recently, Heaven Hill did not have a wheated bourbon, so rye would be in that spent beer. What would that do to their flavor? I don't know, but I am willing to bet Maker's Mark does not want to find out the hard way if it was bad for their flavor profile.
Mike Veach

10-06-2003, 08:30
Let me Shoot this Straight...

This is a fact...

Maker's Mark uses Heaven Hill's backset, (also known in the industry as "slop", slang word)...for start up...

You are dead wrong...

Bettye Jo Boone

10-06-2003, 11:04
Betty Jo,
I stand corrected. It does surprise me though that they would do it that way, but maybe they are trying to keep the use of chemicals down to a minimum. One of the things I admire most about Heaven Hill is the fact they changed the Bernheim distillery around to use jug yeast instead of the bag yeast U.D. was using. I also assume they are not using the enzyme to suppliment the malted barley in the mash. I prefer to see the whiskey made in more traditional methods, so good for Maker's Mark and Heaven Hill for helping them out.

Has Heaven Hill always done this for Maker's Mark, or is it something that just started doing? Was the slop (if you prefer) from some wheated recipe bourbon or a rye? If it was wheated then the chance of changing the taste is reduced.

Mike Veach

10-06-2003, 18:27
You can think of sour mash as an additional step. If sour mash (i.e., the use of set back) isn't done, then it's sweet mash. As Mike said, everyone adds fresh yeast, whether it's a monoculture yeast from bags or a propogated wild yeast from jugs. I have been told that with modern process controls, sour mash isn't really necessary, but everyone still does it because it is the tradition.

10-06-2003, 19:10
I realise there has to be fresh yeast, as for any ferment except where a source is available spontaneously, e.g. from grapeskins in winemaking. Spent wash could not have contributed live yeast cells since the distillation heat would have killed them. I was wondering where the yeast for the successive mashes came from, ie. was it collected from previous ferments (before the boils) or was it made anew for each batch from a pure culture? I think Mike and you answered that, it either is propagated in jugs from previous brews (and thus is wild to an extent but monitored for cleanliness and potency) or is made fresh each time (I read elsewhere) from an agar slant in the distillery laboratory. The bag yeast method sounds like a commercial source of yeast which is a variation on the former method.

If there was a brewery nearby, one could always buy yeast from them, and Byrn speaks of English and Scottish distillers using large amounts of "fresh porter yeast" for this purpose. I should add too he makes a reference at one point to the felt need not to collect yeast from each ferment, that it was left in because it was felt more alcohol was produced (i.e., presumably the mash was turbid from yeast when distilled). This would make sense where they could be assured of buying fresh porter or ale yeast from the many breweries in Britain.

Based on what Byrn says about French methods (1875), sour mash related always to acidity levels and secondarily to an additional ("free") source of fermentable sugar via unfermented sugars or unconverted starches.

I always understood too the jug method of keeping yeast going is a sweet mash no less than any other way of obtaining a yeast source where no backset is used. The use of jug yeast is not (as far as I can glean) related to the term "sour mash bourbon", at least not how it has been used for over 100 years. Mike said the early 1800's woman distiller used the term sour mash bourbon more in the sense connected to sourdough bread, and it would be interesting to learn more about what she meant by the term sour, and sweet, mashes.


10-07-2003, 08:01
As I understand it, the use of backset "sours" the mash, i.e., gives it a slightly sour flavor, hence the name.

You are correct that either jug or pure culture yeast could be used without affecting the "sour mash" designation one way or the other.

10-07-2003, 10:21

I was wondering where the yeast for the successive mashes came from, ie. was it collected from previous ferments (before the boils) or was it made anew for each batch from a pure culture? I think Mike and you answered that, it either is propagated in jugs from previous brews

In a way, it's probably a little of both.
I baked sourdough bread for about a year. The original culture was given to me by a friend, and had to be 'fed' once a week to keep it alive. I would divide the culture, using half to bake bread (or flush down the toilet...we were living on a farm/septic system... http://www.straightbourbon.com/forums/images/graemlins/lol.gif). I would 'feed' the other half with flour. It would show signs of fermentation, just like a mashtub.
What I learned, after a year of doing that, is how much I could change the taste of the bread, by what I 'fed' the yeast.
I'm sure the same thing applies here.

10-07-2003, 12:54
Interesting. In beer fermentation, you would take yeast from a "first" fermenting mash (skim it off) and keep some in a jug for the next one, and so on. That was the traditional way but as mentioned earlier, the yeast would need to be revived/corrected periodically (today, by reference to a single cell yeast isolated in the lab) because it would alter its taste too much or lose power to ferment correctly otherwise. Your bread culture is truly separately made in that you obtained and fed it from sources separate from what was being fermented. In fresh bread, yeast acts on sugars in the loaf to make both CO2 (helps loaf to rise) and (some) alcohol which mostly lifts off into the air, ie. some residual remains in the bread, but just traces. But whatever propagated yeast is created in the bread itself (reproducing itself) stays only in the bread, which is why fresh sourdough and other yeast baking is intensely yeasty in taste. So, there are different ways to keep the yeast in the jug going too..


10-07-2003, 13:11
The other thing this discussion raises in my mind is the effect of yeast on whiskey flavour. Many distillers insist on the importance of yeast in this sense. Lincoln Henderson does in the symposium in the current Malt magazine. Many other distillers have said similar. While beer brewrers know this to be true for beer, initially I was surprised that a mash heated at least to a temperature to make ethanol volatile could transmit that yeast taste to the condensing spirit. Yet, that it must do so seems unarguable. In the current Jim Beam whiskey range, I feel one may be able to detect a uniform yeast taste. It is a dry, lightly astringent, citric-like taste. It is reminiscent in particular of certain Belgian beers (e.g. Chimay, Orval) which are unfiltered. I understand Baker's, Booker's and Knob Creek use different mashbills. Yet, in a recent side-by-side tasting I felt I detected that signature flavour in all of them. It isn't dominant but is a discernible flavour element. Maybe this isn't the Beam yeast but something else I am noticing.. The 1960 decanter Beam brought to the Gazebo '03 did not have that taste at all, so either yeasts evolve over time, or something other than yeast explains it. If I was told Beam uses the same yeast for Baker, Booker's and Knob Creek, to me that's a further suggestion that what I am detecting is a yeast flavour. If the yeasts used in these three bourbons are different strains, that argues against my deduction..


10-08-2003, 21:55
There are some very important topics brought to light here. With regard to "Distillation killing the yeast"--good point, but the backset is taken prior to distillation, while still in beer form.

The variant role that yeast play in fermentation is interesting to say the least. Certainly in brewing, various substrains of Saccharomyces cervisiae (I don't know of any distillers that use Saccharomyces carlsberginsis) create different flavors, as their biochemical processes will vary slightly. This may create more of the interesting compounds left over in the new make spirit such as esters, acetyl aldehydes and heavier fusel oils. There is some interesting research going on right now as to how that affects flavor. Does the ethanol act as a solvent or catalyst for the breakdown of lignin into tannins and vanillins, or do the congeners left over from distillation degrade the intensely ligated cellulose structure.

As far as the yeast are concerned, the proprietary strain will have an effect on the taste of the beer, which will manifest itself in the distillate. There can be no question of that.

Fermenting and brewing require continuity in cultured yeast. This can be done two ways: commercially prepared cultures from the same lab each time, or reculturing (backset)

With regard to "souring" the mash, I am not sure of the definition of "sweet mash". I do know that several distilleries utilize Lactobacillus to assist with "souring' the mash, though I am uncertain of the purpose of this.

10-09-2003, 12:16
but the backset is taken prior to distillation, while still in beer form.

Uh uh. The backset is "spent mash," i.e., post-distillation.

10-09-2003, 13:45
Cowdery, if backset is to be used, as purported, as a starter yeast culture, it would have to have viable yeast in it. 170 degrees F is high enough to break down proteins (ie protein denaturation) in all but the most steadfast organisms (E. coli, Pseudomonas Aeruginosa, etc.), rendering the yeast unusuable. So unless backset is used for some other purpose, which, frankly, I don't know, then it would have to be taken prior to distillation.

If there is a better explanation, please give it. I honestly just want to understand.

10-09-2003, 17:54
The purpose of backset is to condition the new mash so that it is hospitable to the yeast organisms you want and hostile to yeasts and other microorganisms you don't want. It's not a source of live yeast. Backset prevents contamination of the mash by wild yeast and other common microorganisms. Yeast is added to the mash after the backset. Today, distillers use either a pure culture yeast or a jug yeast, which is made by capturing a strain they like from the air and propogating it in a special medium. Even pure culture yeasts are "mixed up" first in a medium that resembles the mash/backset but with some variations. Only after the yeast has started to vigorously do its thing in that medium is it added to the mash/backset in the fermenters.

10-09-2003, 17:55
So unless backset is used for some other purpose, which, frankly, I don't know,


10-09-2003, 19:42
Thanks for the explanation Cowdery. As a microbiologist and brewer, I still fail to see how that creates a more hospitable environment. In brewing, I always keep dregs of the fermented wort for the next batch as a viable culture.

BobbyC, if your comment was intended as I think, you shouldn't have bothered. If not, no problem.

10-09-2003, 20:26
A portion of the spent mash was returned to the fermentation process initially for water content and heat. Along the way someone discovered that it also lowered the ph and hence the "sour mash" process.

10-10-2003, 00:26
Here is Byrn, 1875, writing about French practice:

"For cooling and diluting the substances in course of maceration [mashing], we employ clear spent wash, (clear part of slops), the residuum of beer, the water of breweries, or, if none of these liquids are at our disposal, pure water.

Spent wash is never used unless in admixture with one-half, or at least one-third, of pure water.

There are two principal reasons why we prefer the spent wash to the other liquors: first, because having absorbed the oxygen of the air it helps the fermentation; second, because it marks generally several degrees of the densimeter, which shows that it still contains a certain quantity of sugar, which is thus put to account. Experience also proves that the starch suspended in the spent wash helps the fermentation."

Maybe we are all right here: using backset in 1818 in rough pioneer-like conditions assisted a natural fermentation because it had "absorbed the oxygen", i.e., had submitted to the effect of wild airborne yeasts which were working on the residual sugar in the liquid.

Oxygen is not (I believe) needed for fermentation. This work was written before yeast and its properties were fully understood. It is the absorbtion and action of wild yeast which perhaps "re-yeasted" a wash in which the original yeast would have been rendered ineffective through heating to 172 F. to vaporise the alcohol (and if the wash was very strong to start with, say, 8-10% abv., I doubt very much original yeast would survive in there even before boiling). Now, today, the backset used would be industrially monitored and processed to ensure it was not affected by wild yeasts (in fact I believe modern mashes are sterilized before the yeast is put in - Mike, maybe that's why those prewar whiskeys taste so good, did they do that before 1939? I doubt it!).

Clearly, today, there is something, apart from being a source of recyclable water and some additional fermentables, motivating distillers to use this substance in the successive mash. Along with Chuck and Bobby I always thought the reason was related to beneficial effects on the acidity level. Byrn has another passage in which he talks about desirable acidity in sour mashing, I can't find it right now but will post the wording when I do.

Again, just to plug the book, it can be bought ("The Complete Practical Distiller" by M. La Fayette Byrn, M.D., published Philadelphia, 1875) at www.raudins.com (http://www.raudins.com)).


10-10-2003, 06:54
You are correct, fermentation is an anaerobic activity. The fermetation cycle is a branch of the ATP production cycle utilized if anaerobic conditions are present. The 6 carbon sugar glucose is energized by the addtion of a high energy phosphate, rearranged several times into glucose-6-phosphate, fructose-6-phosphate (a second phosphate is added to form--)fructose-1,6-biphosphate. Fructose-1,6-biphosphate is split into two glyceraldehyde-3-phosphates (G3P) Each G3P undergoes the addition of another phosphate (utilizing NAD+ and NADH as electron carriers) resulting in 1,3 biphosphoglycerate. One phosphate from the molecules is transferred to ADP to form ATP for a net gain of 2 ATP. After rearrangement to form phosphenolpyruvate, the last phosphate is removed by two more ADP molecules, resulting in a net gain overall of 2 ATP per molecule of glucose. This process of glycolysis forms 2 pyruvate molcules per molecule of glucose. Pyruvate (3 carbon chain) then enters fermentation where utilizing Acetyl Coenzyme A and NAD+/NADH, it is further reduced to the single carbon, carbon dioxide and the two carbon alcohol, ethanol.

Now that I typed all that, I can't remember why--LOL!

Okay, so now we know that backset isn't used for oxygen (because yeast don't need it) or as a starter culture (because it is taken from spent beer). I doubt it would be used strictly for pH purposes, since there are far better methods available for accurately controlling pH levels. If it is used simply as a friendly medium for yeast propagation that still wouldn't explain a need for it, as the new wort/mash is a perfect medium for yeast. And, from a biochemical/organochemical standpoint, I don't understand what would be present in backset to cause "souring". Why then would Woodford and Four Roses utilize lactobacillus to "sour" their mash? Why do some distilleries use hops in the mash (presumably to keep the yeast viable and control pH (via isoalpha acids), but why if pH can be controlled by backset?)? How do each of these differing processes affect the flavor of the whiskey?

I believe this is a far more complex subject than many of you are giving it credit for. I would love to have some answers to the above questions if anyone can.

10-10-2003, 07:09
You are right again Bobby http://www.straightbourbon.com/forums/images/graemlins/grin.gif http://www.straightbourbon.com/forums/images/graemlins/grin.gif

The backset (slop) is a major part...in many ways and the "heat" factor is one of them...In the old distillery (that burned)...there was a tub---between the beer well and the still...The beer was pumped into the well...Steam was tuned on to heat it up and to start the "process in motion"...It was pumped out of the beer well and through (pipes) this middle holding tank full "hot" backset (slop) to heat it up further...This holding tank was used for heating purposes only...and then into the still...

The folling is a typical list of "sets"...for a mash operator...

Jug yeast was made fresh everyday...

Single set:



2 Mash....

4 Mash.....

1/2 Yeast..
2 Mash.....
1/2 Yeast..
2 Mash.....

A typical day would be 16-18 Mash tubs a day...One of the tanks held 32,000 gallons...

http://www.straightbourbon.com/forums/images/graemlins/grin.gif http://www.straightbourbon.com/forums/images/graemlins/grin.gif Bettye Jo http://www.straightbourbon.com/forums/images/graemlins/grin.gif http://www.straightbourbon.com/forums/images/graemlins/grin.gif

10-10-2003, 07:26
Sorry Bettye Jo, I don't mean to sound ignorant, but are you saying that backset's purpose is as a source of heat?

10-10-2003, 08:42
Okay, just to clear that previous post up. . .hops are used when propagating yeast, not in mash. SO, here are my questions:

1. Why would backset be used as a hospitable environment for yeast, when mash is already hospitable?

2. I understand backset's use for heat, but why for a water source?

3. Why do distilleries find it necessary to use lactobacillus if backset causes "souring"?

4. Regulation of pH is far easier, more economical and more accurate via other methods, why backset?

5. What biochemical processes does backset involve that alter the mash and the taste?

What I am having trouble seeing here is any real benefit to backset. If it is heat you want, do what Bacardi does and allow methanogenic bacteria to degrade the spent beer and produce methane to economically fire the boilers for all your heating needs. I think a case can be made for it as a water source, since it will contain many nutrients water does not that will help propagate the yeast.

But these are physical statements. What benefit does backset have on the taste? How does it alter the mash? If it doesn't then why haven't more modern techniques been implemented. I have yet to see a clear explanation of exactly what is going on with backset in terms of the chemistry of the process. If anyone can clear this up, please do.

10-10-2003, 09:05
The simple answer is "because that is the way its always has been done". Tradition is a strong force in the industry.

With that said there have been lots of experiments with simple chemical substitutions (enzymes to use less malt, acids in place of backset) but in most cases they do change the flavor of the final product. Distilling is still as much art as it is science. Things happen in the process that still leave people guessing as to why that happens.

I will say this - the old way is better. If you have doubts take a bottle of Weller from the Van Winkle era, a bottle from the U.D. era and a bottle from the Bufallo Trace era and do a side by side tasting. There is a huge difference in taste between the Van Winkle and the Buffalo Trace. The difference is not as stark between the U.D. and the other two, but there is a difference. The big changes from Van Winkle to U.D. is U.D. quit using jug yeast and cut the amount of barley and supplimented with enzymes. The Buffalo Trace being bottled today is the U.D. formula aged in brick warehouses.

Chris Morris tells us that they sometimes don't use backset (or slop if you prefer) to create their sour mash at L&amp;G. Sometimes they just use acid. What the results will be are still to be determined. It does take at least 4 years to get a final product in most bourbons and at L&amp;G it seems to be taking longer.

Mike Veach

10-10-2003, 09:14
That's a pretty freaking good answer. I have no problem with tradition. Since Dr. Crow was a chemist, I just assumed there would be some legitimate scientific reasoning behind doing it that way. None of the bourbon books I have fully explain it, so naturally, I was curious.

So it seems the general consensus is that taking backset is a traditional methond of pH regulation, nutrient-rich water source and a source of heat to warm the mash.

10-10-2003, 09:24
You asked some very good questions and there are probably several Master Distillers that are asking the same questions even as we speak, but as I said, distilling is still an art as well as a science. Some questions still baffle the best in the business.
Mike Veach

10-10-2003, 09:30
I really appreciate the concise response. There was really a lot of material on this thread and you summed it up nicely. I have only talked to 4 master distillers, but it would be an interesting topic to discuss with each of the bourbon distillers and get some sort of consensus.

10-10-2003, 10:26
Yes, and those questions are pertinent and interest me no less. All I am trying, as a non-scientist, to understand is how in 1875 and 1818 backset, by dint of "absorbing oxygen", could be seen to assist a ferment by addition to a fresh mash. And I think it may be because that backset was being used as a culture of a kind because it was fermenting anew through exposure to wild yeast. Not hard to see that that might occur when mechanical refrigeration did not exist and the slops of the time probably contained more sugar than they do today (through less efficient mashing and/or fermenting techniques). Beyond that inference and the fact that we all agree (I think) that spent beer today contains no living yeast, there are many questions not answered. Surely a distillery chemist could clear most of this up..


10-10-2003, 10:33

On very rare occasions...backset is not used...3 days only...Due to holiday shut down and backset is not available...Then, they use water...

You left out a VanWinkle (claim to fame) history note that should be on this post...VanWikle posted it in public where folks could see it clearly...

The sign read, NO CHEMISTS ALLOWED...now that one is one for thought http://www.straightbourbon.com/forums/images/graemlins/lol.gif...

http://www.straightbourbon.com/forums/images/graemlins/grin.gif http://www.straightbourbon.com/forums/images/graemlins/grin.gif Bettye Jo http://www.straightbourbon.com/forums/images/graemlins/grin.gif http://www.straightbourbon.com/forums/images/graemlins/grin.gif

10-10-2003, 10:41
Bettye Jo,
You always shoot it straight! In my opinion "No chemist allowed" is a good philosphy with distillers.
Mike Veach

10-10-2003, 10:46
"Distillers" and "consensus" in the same sentence? Ed Foote once told me that if you put a half dozen distillers in a room and ask them a question you will get 8 answers and a dozen "could be" replies. I guess we will have to ask Bettye Jo if Ed is right. she is the only one who might be able to put the theory to trial at her family reunion.
Mike Veach

10-10-2003, 11:03
I have heard VanWinkle's slogan more than once and I tend to agree with it. However, the distillery chemist has played an important role in most bourbons on the market today. Gas chromatography, improved distillation technique and various other contributions by chemists and scientists have lead this industry in a positive direction.

I am sure the farmers in Scotland scoffed at the Coffey Still initially, too, as a new-fangled technique. However, it is the constant research and pushing of the envelope that has allowed certain distilleries, who do employ chemists, such as Woodford and Buffalo Trace, to be constantly thrust into the limelight. These chemists test new technique, discover what makes bourbon good from the inside out and make sure that the product being produced is of the highest quality, standards and consistency.

They will never account for the Master Distiller's art, but they can be an extremely useful tool for a distillery.

10-10-2003, 11:38
You are right. Chemist have played and will continue to play an important part in the distilling business. When prohibition was repealed Schenley set up a school to train a new generation of distillers since many of them that were around prior to prohibition were either dead or too old to want to go back to work full time. The school trained them in many different scientific fields, including chemistry. I think it not as important as to whether a distiller is trained as a chemist or a biologist, just as long as he (or she someday) respects the art of distilling. Some parts of the process may simply be too random to ever figure out to the nth degree, but a good distiller will know when its right and when its not.
Mike Veach

10-10-2003, 14:59
Okay, so now we know that backset isn't used for oxygen (because yeast don't need it)

Being a semi-scientist, I believe that yeast are facultative anaerobes. They can survive in the absence of oxygen, but don't they require oxygen to actively multiply, ie to produce the sterols necessary for cell membrane production. Oxygen would be critical to early stage fermentation. This is strictly from recollection.
(I tried staying out of this thread for over a week and now I'm in it. Maybe I won't hit the continue button"
Where are you Tdelling? You know this stuff cold.

10-10-2003, 15:16
By saying you are a brewer I take it that is your job, most of us here that do it only claim to be homebrewers. Can you say who you work for? If not , Big brewery will suffice, We'll just guess it's Miller, Busch, or Coors.

Why do some distilleries use hops in the mash (presumably to keep the yeast viable and control pH (via isoalpha acids), but why if pH can be controlled by backset?)

Actually as I understand this one, the hops are used in the yeast mash, which is a separate step from the larger mashing sequence.

What purpose does hops play in brewing, Mick?

Why do distilleries find it necessary to use lactobacillus if backset causes "souring"?

This is done to the Yeast Mash.

As far as" No Chemists Allowed" Which served Pappy VanWinkle well. Jerry Dalton has a Phd in Chemistry, And also is a Taoist mystic. Witness that in Chuck's video while still at Barton he says that whiskey making is a mystical process.

( Made and Bottled in Kentucky , Charles K. Cowdery)

<font color="brown"> Good God give Bill Bruford Some </font>

10-10-2003, 18:31
Okay, here is my theory as a non-scientist. Backset was (is?) lightly acid because the residual sugar was being attacked by airborne (wild) yeasts. If backset wasn't heated to a high enough temperature before addition to a new mash, wild yeasts would continue to work - what Byrn calls "the acetic fermentation". Therefore, home distillers by 1818 figured out that using (non-sterile) backset could ferment, or help to ferment, a new mash. It was thus a substitute for fresh yeast or fresh yeasty ale when the latter could not be found. Likely it wasn't an ideal substitute because wild yeast strains might make a mash that might not taste good, but any harbour in a storm.. No doubt home distillers found out too that backset contained unfermented sugar and/or unconverted starches (the two things go together... This was an added bonus but Mike's early 1800's woman distiller seems to have been focusing on fermenting power for the new mash.

Fast forward to 1875. Here is Byrn again on what clearly is sour mashing. Again he mentions this topic only under the heading of French distilling, not in the sections on domestic practice):

"In a continuous work the spent wash should be deposited in vats or cisterns constructed for the purpose.... This liquid may be successfully used in subsequent operations to dilute the grain after it has been mashed. In this practice is found the advantage of bringing again to fermentation a liquid containing some fermentable substances which have escaped decomposition. This may be followed up for several successive operations - that is, three, four and even five; and the grain produces thus as much as 60 litres of spirit of 19 [degrees] per metrical quintal, [a] produce very considerable, and which could not be obtained by any other means. The use of spent wash is suspended when, after several successive operations, it is become so sour that instead of offering proper aliments to the fermentation, its acidity would be obnoxious to it."

This seems rather clear. Spent wash in 1875, in France at any rate, finds its value in its quantity of residual, fermentable sugar (or, convertible starch). More alcohol can be produced for less money from the same stock of new grain if backset is added. Note Byrn does not refer to the fact that backset may have fermenting properties - he ignores that aspect and stresses backset is brought "again" to fermentation. (No need to bring it "again" if it already "is" in fermentation). But clearly, if the backset, as he knew, is acid, and if successive mashes using backset became more sour until it could not be used anymore, he knew there could be a fermented quality to it. Likely in his time they were not heating the backset to sterilize it. But he was in any case interested to get the greatest yield of alcohol from the sugar it still held. He didn't (it seems) care about the wild yeast or acidity factor except to the extent it actually stopped (not assisted) a proper fermentation. The main fermenting power in his system came from fresh yeast - "fresh porter yeast" he calls it at one point; who cares if a few wild spores affected its performance? Today, the "thin" stillage (the solids are taken out) are sterilized before addition to the new mash. Maybe this was not done in 1875 and that is why the backset/mash combination would sour too much after 4 or 5 applications. There must have been some exotic tasting brews and distillates in 1818 and maybe even in his time - maybe some tasted better than today's clean ferments, who knows? Anyway, he seems to have been interested in the additional alcohol that could be produced for "free" from what was otherwise purely a waste product; in this sense, sour mash seesm to have evolved in its meaning from 1818.

Whether backset is used today mainly as a source of extra fermentables is something I don't know - we need distillery chemists to tell us - they must know the chemistry of the process fairly well. Possibly taste consistency is a factor too when batches are prepared in continuous fashion like this. As many have stated, adding (always sterile) backset seems to adjust the PH level to the desired level. Not that there aren't other ways to adjust the PH. Why then is the old way still used, and why is PH adjustment important anyway? How does this relate if at all to the 1875 idea of backset containing additional fermentable materials?

In many ways, the Byrn book is sophisticated - his chapters on continuous distillation are complex and compelling - they had full columnar distillation, they knew exactly how to manipulate the columns to get straight whiskey of the traditional type or the most rectified neutral spirit we can get today. His knowledge of organic chemistry and micro-biology was primitive, but anyone reading him (setting aside his priggish literary style) has to be impressed with his methods and practical savvy.


10-10-2003, 18:43
more alcohol can be produced for less money

" Because the addition of Backset also helps the yeast produce more alcohol, more whiskey can be made from each batch."
P.212 Book of Bourbon

Gary, it appears as though the accountants were there all along! http://www.straightbourbon.com/forums/images/graemlins/grin.gif

10-10-2003, 18:50
Bobby, you got it. http://www.straightbourbon.com/forums/images/graemlins/smile.gif


10-11-2003, 05:48
Pepcycle, I should have been more clear. Yeast don't need it for fermentation.

10-11-2003, 05:51
Bobby C, I corrected myself on the hops used in the yeast mash. However, the use of lactobacillus in the yeast mash, will affect the rest of the mash.

10-11-2003, 13:05
Just a few further thoughts based on additional reading. The role of bacterial action in backset cannot be overlooked. Traditionally (1800's) backset no doubt contained lactic acid (via the action of naturally occurring lactobacillus), and no doubt still does on a controlled basis. Also, I feel wild yeasts may have been at work sometimes in the old backset, hence its appeal for home distillers looking for a yeast substitute in 1818. Today, backset is heat sterilised before being added to the mash and will not have live yeast in it, but its acid levels from the action of lactobacillus may hold the key to its continued use, that and its source of any additional fermentables as earlier discussed. We know yeasted mashes work optimally at a certain pH level. Too much or the wrong kind of lactobaccillus culture will prevent a proper fermentation (the yeast can't work), but the right and proper amount will facilitate fermentation: this is what I understand Chuck Cowdery to have said earlier and that is undoubtedly correct. Specifically, there appear to be certain bio-chemical pathways shared by the by-products of yeast and certain beneficial, symbiotic bacteria. Hence the malolactic fermentation methods, innoculation of mashes with lactobaccillus culture and the continued use of backset due to its natural acidity. The chemistry and biology of these processes are dauntingly complex. I await further information (whether from laymen or scientists) to elucidate one of the key processes in making bourbon what it is.


10-12-2003, 17:29
taking backset is a traditional methond of pH regulation, nutrient-rich water source and a source of heat to warm the mash.

I'd say that's a fair statement.

To really understand, you have to go back to 1840 or thereabouts. The big problem distillers have is consistency. Even if the distiller controls his yeast properly between batches it can get away from him during the actual fermentation, primarily due to interference from wild yeast. He discovers that backset seems to control this, leading to a more consistent beer from batch to batch.

I have been told that today they probably could control the process in other ways and people are always tinkering, but there's a strong bias to just stay with what works.

10-12-2003, 17:38
At the outset of WWII, some bourbon distilleries tried to convert themselves to the production of industrial alcohol. It happened again in the 70s when bourbon sales collapsed. Both times they had a hard time making the conversion. Bourbon distilleries are not about using the most efficient and economical method to convert grain into alcohol. They are about making quality whiskey. If you want to know the most productive way to convert corn into alcohol, go to one of the distilleries in Iowa or wherever that makes industrial alcohol. I imagine they don't mess around with nonsense like backset.

10-14-2003, 20:12
I can't really see how it would be a problem to convert to distillation of industrial alcohol. Did they use pot distillation at that time? I thought pretty much all pot distillation had been phased out by then, with a few notable exceptions. Column distillation 5 times will yeild close to industrial alcohol.

I don't think backset really has anything to do with distillation, just regulation of the mash, and if that is the case, then most distillers would use that process for the mash.

10-14-2003, 20:13
Gillman, another excellent point. If lactobacillus are utilized at any point in the fermentation, whether prepping yeast or in the mash, it will affect flavor.

10-15-2003, 21:41
All I was getting at is that making bourbon is different than making alcohol and some of the process is taken on faith, "because that's how my daddy did it."

10-16-2003, 04:26
Ahh. . .I see what you were getting at. . you are correct!

10-20-2003, 07:24
Hello, StraightBourbonians!

I've been in the Caribbean for two weeks, and didn't have a chance to
do any recreational web-surfing. It looks like you've been rather
busy! This is a most excellent thread!

>Where are you Tdelling? You know this stuff cold.

That's very flattering! I'm really just a whiskey enthusaist with a
predisposition towards chemistry, a voracious reading habit,
a do-it-yourself attitude, and a few homebrewer friends.

I'm very glad that there are now other people on StraightBourbon
with an enthusiasm for bourbon chemistry. I remember getting
funny looks around here for saying "gas chromatography".

It looks like you guys have pieced together Sour Mash pretty well
without me! The one thing I've learned about whiskey is that the
more you learn about traditional techniques, the more the mystery

Just a few words:
1) As someone pointed out, whiskey mash is indeed absolutely crawling
with lactic acid bacteria. This is a totally foreign concept to
homebrewers, who try their darndest to keep such things out, and just
throws a monkey-wrench into their understanding of the bourbon process.

2) Yeast are interesting creatures. Not only are there huge variations
between strains, but a given strain will also behave differently depending
on how it was propigated. Availability of oxygen is an important variable
here, as are nutrients, pH, temperature, etc. So the mysterious and
superstitous methods for yeast propigation are important.

3) I am only just beginning to understand the history of distilling
from a scientific point of view, but it looks like things such as
the sour mash process become infinitely more interesting and complex
when historic (what we would call "crude" and "uncontrolled") techniques
are used.

Tim Dellinger