Sweet Mash -vs- Sour Mash

[boone]

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

[bourbonv]

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

[cowdery]

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.

[Gillman]

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.

Gary

[cowdery]

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.

[brendaj]

Gary,

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... ). 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.

Bj

[Gillman]

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..

Gary

[Gillman]

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..

Gary

[mickblueeyes]

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.

[cowdery]

but the backset is taken prior to distillation, while still in beer form.

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

[mickblueeyes]

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.

[cowdery]

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.

[bobbyc]

So unless backset is used for some other purpose, which, frankly, I don't know,

Exactly

[mickblueeyes]

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.

[bobbyc]

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.

[Gillman]

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).

Gary

[mickblueeyes]

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.

[boone]

You are right again Bobby

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:

Backset...

Mash......

Yeast.....

Backset...

Double....

Backset...

Yeast.....

2 Mash....

Backset...

4 Mash.....

Backset....

1/2 Yeast..

2 Mash.....

1/2 Yeast..

2 Mash.....

Backset....

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

Bettye Jo

[mickblueeyes]

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

[mickblueeyes]

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.

[bourbonv]

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&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&G it seems to be taking longer.

Mike Veach

[mickblueeyes]

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.

[bourbonv]

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

[mickblueeyes]

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.

[Gillman]

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..

Gary