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Jun 08, 2022 View:

Identifying Infection

While still a rookie compared to most on the forums, I've ran my share of runs and been fortunate but for the odd bacterial infection back in the "white bucket days". Unfortunately we have something in house that has infected an ferment later in the process over the holidays when we let a ferment sit.

The mash was wheat, oats, rye and final pH 3.39 FG 1.002. Because of the holidays (and being unable to start the truck because of -31F weather), we couldn't strip it for two weeks. The pellicle showed up between day 12 and 14. Smell coming off of it is pleasant and fruity, but as expected with the pH it is sour. Curious about the infection, partly because of the ferment and also because of seeing it once when our "lauter bin" didn't drain properly. I am leaning towards lacto but humbly welcome input.



Take a sample and look at the pellicle. If it breaks down in to little balls it could be Pichia. If you mill in the same area as you ferment you likely have a mixture of infections.

Infections aren't necessarily a bad thing. It helps with ester formation. If you get an infection after the main part of your fermentation is done it doesn't affect yield significantly. I would still sanitize your fermenter afterwards as early infections will decrease yield.


I have seen something similar.  Happens a few days after an all grain fermentation if it's not run right away.  Doesn't appear on other fermentation even in the fermenter.  Doesn't seem to cause issues.  The way to not get it is to run right away.  


Pretty much impossible to pin down a bacteria/fungi without plating a sample. You can speculate that it probably has a acid compound due to it having a low pH. Possibly a carboxylic acid such as acidic acid which when mixed with ethanol (esterification) will give you ethyl acetate which smells of pears. Furthermore, a carboxylic acid mixed with ethanol can form a alpha-hydroxy group such as lactic acid, hence the low pH. Again, hard to narrow down the exact carboxylic acid without knowing the bacteria/fungi, but there are plenty that have great aromas after esterification. 

As @Foreshot mentioned, it can be seen as a positive condition because of the esters. Unfortunately the large distillery of the last century have not advance fermentation much and only focus on the production of ethanol wheather it be neutral grain or whiskey, which gets its flavor from the barrels. The only industry close is Jamaican rum with the use of dunder pits. As a former brewer, I find the use of controlled fermentation and bacteria to create esters that can enhance any distilled product (including whiskey with light barrel use) very intriguing. IMO more distilleries should focus on quality of product through ingredients and controlled fermentation as well as distillation to create unique esters/flavors. I suspect as more craft distillers pop up this will become more common as it was in the beer industry. This is a time of innovation in our industry which is why i have moved in this direction. Sorry of the rant....

If I were you I would embrace this as a one-off experimental product. Take a sample to know what is causing the condition. Run the was through your still and after you have collected the majority of ethanol, take many small cuts of your tails and separate them in containers. You can then sample them to see what ester you get and mix them back into the ethanol in different volumes till you get the product that is best. Carboxylic Acids have very high boing points, so take deep cuts into your tails. Also, document everything well and with your wash sample you will be able to replicate the product if it turns out well.

Or just ignore what I said and dump the wash or run it for the ethanol only. But if your anything like me, what I have just said will spark interest in the geek within you. 


Thanks, that's great feedback I dont mill onsite but I do keep milled grains in the room. Sources that i will keep my eye on are our closed loop CLT and our floor drain. This was a bit of an experiment using a partially open fermenter (milk tank) instead of our normal fermenters. As a science geek to begin with (but slept through most of my microbiology courses apparently), I will do as  you folks suggest and run the experiment. Thanks for the heads up on the carboxylic acid and late tails cut, I wouldn't have thought of it.




I have a dream that one day we can strike the word "infection" from the distilling vocabulary.

We love mixed bacterial fermentation, and routinely use at least a half dozen strains of non-yeast microbes in fermentation.  Even the brewing community has begun to embrace mixed-culture fermentation in a big way.  Yesterday's infection is today's purposeful inoculation.

Keep in mind that a whiskey wash that doesn't go through a boil post saccharification is going to be absolutely loaded with a plethora of non-yeast bacteria that will flourish during fermentation, especially protracted duration fermentation.  Fermenting in open top tanks?  Fermenting in wooden fermenters?  This is all about cultivating non-yeast microbes.  As interesting as different yeast strains are, bacteria are 10x so.

Indigenous yeast and bacteria are part of the terroir that defines a product.  Operate long enough, and it's likely that your distillery develops it's own unique profile of house strains, which have become dominant in the environment, both yeast and bacteria.

I'm not saying to operate in a unsanitary way, or to eschew sanitizers and GMP, there are plenty of bugs to be avoided at all costs.  I am saying that this is the next frontier in craft distilling, and we need to stop worrying and learn to love the funk.


Heck, Lallemand is now selling 250g bricks of a pure strain of Lactobacillus Plantarum for commercial brewers (and me).

It's a beautiful option for someone looking to experiment with bacterial sour mashing.  The strain is a low acetic acid producer, which is a big plus.  High acetic LAB are negative in the fact that they create a large amount of ethyl acetate, which results in needing to take a larger-than-normal heads cut.  @Broken Anvil Distilleries - you might find this to be the case when you distill that wash.  The heads cut will likely be more fragrant than typical, however the ethyl acetate aroma may overpower.  It's late heads where you need to pay particularly close attention, and you might consider taking a slightly headier hearts cut as a result, and expecting a slightly longer maturation time.  Like @Ironton says, go old school and collect in jars, ESPECIALLY through the mid heads through early hearts.  You can not do this straight off the still, this not possible, I don't care who your great grandpappy was.


Last comment, I promise.  You will never be able to tell what microbial strains are active from the pellicle.  You need to plate, slide, stain, and break out your microscope to even wager a guess.  Some times you get a few clues that can help you hone in on maybe one contributor, but in this case, you probably have a host of microbes active.  That photo is only a small cross-section of the fermenter, but there isn't anything in that small snippet that would cause concern.  Mold, fuzz, dark spots, slimes - these are the kinds of things you'll want to watch for.

Christ, one more comment, then I'm going away to shovel this blizzard.

Brett is what you want to watch out for, especially high phenolic brett strains.  While the beer guys love them, I suspect the distillers will hate them.  The phenolics come through with the hearts, and with a big brett contribution, you'll get big band-aid.  Perhaps in a high peat whiskey, they might work synergistically with the peat phenolics, but in most everything else it's a fault.  That pretty white pellicle on the right, I'd say 25% chance that's brett, with the rest being the typical LAB strains.  Start here -



Honestly I can't believe we don't get into the geekier side of things on this forum more. Esters are a huge hole to go down. I would love to get deeper into your guys experience with them. Phenolics are another area that is interesting. 

Thanks SCD & Ironton, I'm always interested in hearing what people have to say about developing flavors. 


Brett is a very fun one to play with and luckily for me I am a few blocks from Chad at Crooked Stave who is famous in the Beer industry for his assertion on Brett, specifically estery strains vs phenolic strains. For our Rum, I am currently experimenting with b. anomalus and b. custerianus to create fruity esters as apposed to the more common b. bruxellensis which creates more phenolics as @Silk City Distillers mentioned. Samples from dunder pits that gave the "rum oil" that is favored in the Jamaican Rums have shown presence of Clostridium, specifically c. butyricum which is responsible for the same fruity esters. 

I agree with phenolics being more important for a peat whiskey and potentially any whiskey for that matter considering that one of the most important flavor producing aspects of barrel aging is the tannins of polyphenols. I will be doing some experimenting in this real, after I finalize our Rum. The only bacteria we are using currently for whiskey is Lacto in our Wheat Whiskey. This is a collaboration with Blue Moon which is essentially a Berliner Weisse. Kettle sour 60% wheat mash that they ferment on blueberries, us without, then we distill and barrel age. It has a nice fatty fruity aroma that leaves an after taste similar to a white gummy bear. Signature drink is a blueberry whiskey sour to bring it back to the blueberries Blue Moon uses. 

Let keep the conversation going as we all do more experimenting!



Good luck with the Brett in rum, if you get decent results from anomalous or the others let us know.  I tried a few strains, mainly brux and lambicus (still brux), they were all big fat fails.  Rum does not lend itself to the phenolics like whiskey, there is nowhere to hide from the big fat rubbery medicinal band-aid.  It doesn't age out either.


Propionibacterium Shermanii is very easily sourced (common in cheese production, you can source pure cultures in pitchable volumes), likewise Clostridium Butyricum (not a botulinum toxin producing strain), also easy enough, but needs to be propagated.

These two in conjunction with whatever your preferred lacto can create enough ester funk to put Messrs Wray and Nephew to shame.



@Silk City Distillers from what kind of companies do you source your bacterial cultures. Can't seem to find descent priced cultures here in Europe. 



You'll be able to find propionibacterium shermanii very easily, it's what cheesemakers use to give swiss cheeses like emmenthaler or jarlsberg it's bubbles.  Any wholesaler of cheese-related cultures can supply it, or likely any hobby cheesemaker supplier.

A little Google-Fu and you'll find something.  For example, here is one in UK, very affordable quantities:

At a minimum I would suggest co-pitching with a lactobacillus strain, in a non-refined sugar wash that includes a portion of backset.