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Hypnopooper

my mash soured...

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I was making a 27 gallon test recipe using 72% steam rolled corn, 18% flaked rye and 10% malt. This was my second attempt, but with a different outcome. First attempt didn't sour during fermentation and seemed fine after some light aging.

When I made the mash I did not utilize any wort chillers, so, it took several hours to cool from 200F to 160F, then to 155F. It was late and I was tired, so I decided to add the malt at around 155F instead of 152F and went to bed to let the wort finish cooling. When I checked on the mash the next afternoon (12hrs later), it was still arount 120F and it appeared to slready be fermenting on the top cooler layer. I hooked up my improvised wort chiller running with a glycol solution to bring the mash down to 75F. This took about 2 hrs and then i pitched my yeast. When I was pitching the yeast I had noticed my wort had soured. It appears that it is fementing fine, but I am wondering if I should be concerned even bother distilling it.

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In my personal opinion, keep it going. It will most likely have a different taste, probably quite fruity. You are a "craft" distiller so experimenting is all part of the experience. Your alcohol yield might be lower.

I lauter rye which is notoriously very slow. My mash always sours before it finishes running off. I think that is part of the reason for the unique flavour of my spirit.

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Souring a mash is not a happy thing to happen. Slow cooling mashes provide a ripe environment for spoilage. If you have a common lactic acid fermentation nothing is really bad. There are several infections that are not pleasant at all. One way to help prevent the temperature tolerant bacteria from infecting your mash, which is usually introduced with barley malt for conversion, is to pasteurize your mash after conversion is complete. Beer brewers get this automatically with the hops boil. Distillers are often caught off guard by streptococcus thermophilus, which can survive 155f for several hours. It takes only 15 minutes at 160f to get rid of it though.

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Thanks Sherman! I have followed some of your how to's via You tube. I think its lactic acid as I am not getting the cidery vinegar smell. Next time I will crash cool since I have completed my glycol chiller project, and this result is not good for trying to create a repeatable process. I'll probably go ahead and distill it to appease my curiosity.

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I believe the sour mashing benefit you are refering to is the addition of sour mash to the subsequent bactch. Not necessarily a soured mash. The difference being sour mash uses previously fermented wash/mash that has a lower pH due to the production of CO2 and acids, by the yeast during fermentation, and possibly from lactic acid formation due to lactobacillis (if present). The benefit of adding sour mash is that it quickly reduces the pH of the mash, inhibiting the growth of many (not all) bacterial strains, while at the same time making the mash more suitable for yeast growth. This, combined with rapid cooling of the mash, and oxygentation, allows the yeast to out compete the bacteria that lead to a soured mash. The soured mash mentioned in this thread sounds a lot more like bacterial infection than the desired pH reduction of fermentation. I second Sherman's recommendations, try pitching the yeast with a more sanitary mash, by sterilizing the mash after malt introduction, or use enzymes in place of malt.

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A couple of big bourbon distillers use a sour yeast mash. Most innoculate with a know strain of lactic acid bacteria. But in the past it was simply left to sour over night. Then heated to kill the bateria, cooled, then yeast added. Makes for fruitier flavors in the distillate I have found.

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A couple of big bourbon distillers use a sour yeast mash. Most innoculate with a know strain of lactic acid bacteria. But in the past it was simply left to sour over night. Then heated to kill the bateria, cooled, then yeast added. Makes for fruitier flavors in the distillate I have found.

Are you sure about that technique ? Re-heating a mash to sterilization temps is a very expensive extra-step operation that would be unconscionable in mass production distilleries.

I don't care to re-kindle the 2yo thread referenced, but there are a lot of half-truths in that mix.

1/ German brewers following Reinheitsgebot cannot add acids to the mash, so they perform a long, low-temp (mostly lactic) 'acid rest' before the regular mash cycle get get some lactic souring (alternatively they add 'sauermalz' - re-dried malt that has participated in a lactic fermentation). Of course brewers will boil/sterilize their wort after the mash as Sherman notes. Most brewers merely add phosphoric, or hydrochlorus acid to the mash (rarely lactic, as it imparts flavor to beer).

2/ To get optimal mash conversion it's necessary to control both the mash temps and pH (~pH 5.2), and acid addition (in some form) are needed to overcome the buffering effect of hard water and nearly all water sources are hard enough to require acidification. This is clearly why sourmash backset is used in the mash (not fermenter) to overcome the hard limestone water carbonate buffering.

3/ Common brewing & distilling yeasts are fully capable of reducing wash pH to it's terminal level without pre-acidification, however shifting the pitching pH down to ~pH 4.5 is advantageous, particularly for high gravity ferments (above 15Plato) according to Narziss.

4/ Mixed fermentation (some lacto + some yeast, or even two yeasts) is inherently unstable and unpredictable, not appropriate for any quality controlled process.

There are good plausible reasons why stillage backset sourmash, as opposed to direct acidification w/ lactic or phosphoric, could result in improved flavor/aroma, however I don't see how this can apply to the BT/EH-Taylor pocess. OTOH EH Taylor is pretty tasty, so I won't argue with success.

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Yes, I am 100 percent positive this is how a couple big distillers make their yeast mash. I learned it from down there. It is a very traditional process and yeilds postive results. Now BT soured an entire mash that way, I do not know the whole scoop, but I imagine they killed the lactic in it some how before thay yeasted it, maybe not.

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Also, the use of thinset or backset in a fementer is critical to flavor production of bourbon and rye whiskey. It adds calcium and nitrogen to the mash that help the yeast do their job.

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Acid control of the fermentables is an important step. Starch conversion via alpha amylase enzyme reaction (read, malt) is maximized within a narrow Ph band, as well as a narrow temperature band. As mentioned, an acid rest at around 38 deg C was used by many brewers using decoction or step mash techniques...the phytase rest is a good option if you have time and lots of undermodified malts, but with today's malt having diastatic superpowers, it is relatively rare. Why spend an hour or more at low temp, when you can simply toss in some acidulated malt or even some citric acid?

When making sake, the yeast syoubu is prepared with a boiled polished rice, and inoculated with a lactobacillus to sour the mash. Once the acid level has reached a certain point (after about a day) the syoubu is inoculated with yeast...the lactobacillus is aggressive enough to kill off any bacteria that may outcompete the yeast. In a traditional "yamahai" sake, the syoubu isn't inoculated with lactobacillus...instead the toji waits for the syoubu to infect naturally with a lacto, and uses that. It takes quite a bit longer.

Personally, if a mash "soured" spontaneously, I'd try overpitching. Having said that, I'd also plate the liquid and make sure it's not a strep or pedi infection. Most infections can be forced out with an aggressive yeast. I'd not say that for beer, but we're producing alcohol for distilling, here. You can reheat the mash to about 170 F, and that should kill most things that would present a problem. Then repitch. If you find there is an unpleasant off-flavor, make sure it doesn't happen again!

Some belgian beers are sour mashed to increase acidic mouthfeel, but they are fermented on Brettanomyces and further soured.

After discussing this with a friend and mentor distiller, he mentioned that soured mashes, when soured with a lacto, tend to help in two ways. He said that lower Ph in the wash makes it easier to clean the pot, and keeps the mash from sticking to the copper. He also said that alcohol distilled off of a sour mash has a "softer" mouthfeel. He couldn't offer me any scientific explanation for these, but I'm inclined to bow to his vastly superior experience :rolleyes:

Hope some of this helps....

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@Hypnopooper what were the results of this?  How did the ferment turn out?  Did you distill it? Age it?  I have the same thing going on and I am curious.

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