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  1. #41
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    Re: Sweet Mash -vs- Sour Mash

    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

  2. #42
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    Re: Sweet Mash -vs- Sour Mash

    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.

  3. #43
    Bourbonian of the Year 2004 and Guru
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    Re: Sweet Mash -vs- Sour Mash

    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


  4. #44
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    Re: Sweet Mash -vs- Sour Mash

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

  5. #45
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    Re: Sweet Mash -vs- Sour Mash

    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.

  6. #46
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    Re: Sweet Mash -vs- Sour Mash

    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

  7. #47
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    Re: Sweet Mash -vs- Sour Mash

    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.

  8. #48
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    Re: Sweet Mash -vs- Sour Mash

    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

  9. #49
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    Re: Sweet Mash -vs- Sour Mash

    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. #50
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    Re: Sweet Mash -vs- Sour Mash

    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

 

 

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