Mystery substance

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didoato

didoato

RichyD
Joined
Sep 11, 2022
Messages
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Location
Delaware
Can someone help me identify the mystery substance I found in my fermenter?
I was kegging a batch of stout and saw white substance in the fill line, when I opened the fermenter (after the fill) I saw the white substance pictured. Where it was adhered to the fermenter wall it was fairly thin (a millimeter or two), had a chalky feel when touched. It seemed to have been floating on top of the wort.

Methods/notes
This batch was a full grain stout.
I use RO water and added water conditioning chemicals in the mash water (6.5 gal) as follows:
gypsum 1.2 tsp
epsom salt .2 tsp
calcium chloride .4 tsp
baking soda .8 tsp
I am pretty meticulous in cleaning and sanitizing pre-fill - I use PBW wash and sanitize with starsan
The fermenter was sealed after yeast pitch
This is an Anvil Chronical - I drained trub using the 1.5" port after one week - this pulled in some air.
It has been in the primary fermenter for three weeks.
I left the wort sit overnight - mold has formed (of course) on top of the wort - it does not look like the white stuff pictured.
Thanks

WortStuff.jpg
 
Last edited:
Ye, it's the shreds of a bacteria pellicle- possible acetobacter. Nothing to do with you cleaning regime as it's airborne. If you get a faint whiff of vinegar, don't worry, it won't increase once the beer's kegged or bottled as it needs oxygen to multiply. (It could even serve as an anti-oxidant).

Only joking, but it really could.

Don't reuse the yeast from that batch.
 
It's always a little risky trying to identify a bug from a picture, but it does kind of look like Acetobacter. Have you seen any fruit flies around?
 
VikeMan said:
It's always a little risky trying to identify a bug from a picture, but it does kind of look like Acetobacter. Have you seen any fruit flies around?
Click to expand...
I have seen a few fruit flies n the kitchen, but not in the basement where I store the fermenter.
 
I had a huge problem with the same ongoing infection (just judged by the look of it). It doesn't render the beer
undrinkable but it kills the head retention and with time also the taste.

My solution was switching from a bucket to a truly airtight fermenter, in my case a Speidel. These little critters are everywhere, you cannot get rid of them completely and once they get some oxygen, they start to thrive in your beer. No oxygen, no acedobacter. Worked for me.
 
didoato said:
I have seen a few fruit flies n the kitchen, but not in the basement where I store the fermenter.
Click to expand...

My guess is that one or more got into that batch sometime post boil.
 
didoato said:
It has been in the primary fermenter for three weeks.
I left the wort sit overnight - mold has formed (of course) on top of the wort - it does not look like the white stuff pictured.
Click to expand...
When did you leave it sit overnight? Right after you brewed it? Before you pitched yeast?
In what kind of vessel was it stored? Covered?

What makes you think it was mold?
 
IslandLizard said:
When did you leave it sit overnight? Right after you brewed it? Before you pitched yeast?
In what kind of vessel was it stored? Covered?

What makes you think it was mold?
Click to expand...
I use a stainless fermenter, only introduction of air after boil/cool down/transfer was to drain trub - it is an Anvil stainless with a 1.5" drain - on draining trub after one week I had to let in some air to break the vacuum (I dont have a co2 gas connection for the fermenter yet).
No reason to think it was mold, just throwing it out there.
 
didoato said:
I use a stainless fermenter, only introduction of air after boil/cool down/transfer was to drain trub - it is an Anvil stainless with a 1.5" drain - on draining trub after one week I had to let in some air to break the vacuum (I dont have a co2 gas connection for the fermenter yet).
No reason to think it was mold, just throwing it out there.
Click to expand...
Sorry missed the key point of when it sat overnight - I left it sit overnight after I kegged it.
 
didoato said:
I use a stainless fermenter, only introduction of air after boil/cool down/transfer was to drain trub - it is an Anvil stainless with a 1.5" drain - on draining trub after one week I had to let in some air to break the vacuum (I dont have a co2 gas connection for the fermenter yet).
No reason to think it was mold, just throwing it out there.
Click to expand...
Better let it sit on the trub next time. The additional O2 at that time of fermentation does harm. The trub doesn't.
 
didoato said:
I use a stainless fermenter, only introduction of air after boil/cool down/transfer was to drain trub - it is an Anvil stainless with a 1.5" drain - on draining trub after one week I had to let in some air to break the vacuum (I dont have a co2 gas connection for the fermenter yet).
No reason to think it was mold, just throwing it out there.
Click to expand...
When breaking vacuum, I use a sanitary air filter in the air intake. One of those used for aeration. Easy and cheap.
 
Any chance a fruit fly got into your yeast starter, if you did one? Happened to me once, and I was told my my club's resident brew guru not to risk it and to dump it make a new starter, that just one fruit fly could infect it, so why take a chance.
 
didoato said:
it is an Anvil stainless with a 1.5" drain
Click to expand...
Make sure to thoroughly clean and sanitize everything that touched your (infected) beer, including that drain, valve, hoses, fittings, etc. Those bugs, whatever they are, are in your beer and thus anywhere.

didoato said:
No reason to think it was mold, just throwing it out there.
Click to expand...
Oh, good. ;)
That pellicle probably grew and closed during the overnight stay. Pellicles are harmless, but they do tell you something wild got in there having a jolly good time. Sometime that's intentional (e.g., making sours).

Pellicles can take on many forms, from a slight haze, "broken ice shards" (like yours), "slimy" bubbles, to thick, gnarly rugs, always trying to cover the whole surface, as that's what protects the microorganism underneath from intruders.

BTW, we have a 67-page picture thread on pellicles, many are truly beautiful:
https://www.homebrewtalk.com/threads/pellicle-photo-collection.174033/page-67
 
dmtaylor said:
Replace all your o-rings, gaskets, and hoses.
Click to expand...
Nah, good thorough scrubbing and cleaning in hot (homemade) PBW, and be meticulous at sanitizing and inspecting.

Perhaps a bleach bath on the plastics and rubber items.
But NEVER use bleach on stainless!
 
Don't worry too much about seeing fruit flies or not. They carry the bacterium but look at this from wikipedia:

All acetic acid bacteria are rod-shaped and obligate aerobes.[1] Acetic acid bacteria are airborne and are ubiquitous in nature. They are actively present in environments where ethanol is being formed as a product of the fermentation of sugars. They can be isolated from the nectar of flowers and from damaged fruit. Other good sources are fresh apple cider and unpasteurized beer that has not been filter sterilized. In these liquids, they grow as a surface film due to their aerobic nature and active motility. Fruit flies or vinegar eels are considered common vectors in the propagation of acetic acid bacteria.[2]

You'll need more than a rinse round with a bit of metabisuphite, but it's not cause for paranoic cleaning. Dilute bleach, unscrew taps and give the threads a bit of a seeing to with a toothbrush and then when eveything's ben soaked, use matabisulphite to kill the chlorine in the bleach. That pellicle you saw means they like to stay on the surface, indeed, they can't survive without air. This probably happpens to all of us at some time or another, especially with beers that are maturing in bulk and the air seal (airlock or whatever) has run dry.

Some styles, mainly Belgian, use acetic acid bacteria deliberately as part of a souring mix of bacteria. The important thing is to get it bottled up as soon as you detect infection. Once bottled, the beer's safe.
 
An Ankoù said:
The important thing is to get it bottled up as soon as you detect infection. Once bottled, the beer's safe.
Click to expand...

Well, it would be safe (i.e. couldn't make more acetic acid) if you could avoid introducing new O2 during the bottling process and prevent O2 ingress (via the cap to bottle interface) after bottling. But neither is really possible. And people have had acetobacter infections that didn't become evident until some time after bottling. But it would probably be fair to say that bottling will slow acid production down to minimal levels, as compared to beer continually exposed to larger amounts of O2.

Personally, if I had an acetobacter infected beer and the taste was tolerable, I'd also keep it as cold as possible. Acteobacter species tend to get sluggish at low temps.
 
An Ankoù said:
Some styles, mainly Belgian, use acetic acid bacteria deliberately as part of a souring mix of bacteria.
Click to expand...
Lactic Acid, yes!
But Acetic Acid, no! At least not deliberately. They do their best to prevent Acetic Acid production as much as possible. Sometimes a little of it is produced along with the yummy flavors they're after, which is the exception, and only acceptable as long as it remains very restraint.
 
IslandLizard said:
Lactic Acid, yes!
But Acetic Acid, no! At least not deliberately. They do their best to prevent Acetic Acid production as much as possible. Sometimes a little of it is produced along with the yummy flavors they're after, which is the exception, and only acceptable as long as it remains very restraint.
Click to expand...


well as long as it's not ergot, and lysergic acid no one will start tripping over it.....
 
Lucio Fialho said:
When breaking vacuum, I use a sanitary air filter in the air intake. One of those used for aeration. Easy and cheap.
Click to expand...
An Ankoù said:
Don't worry too much about seeing fruit flies or not. They carry the bacterium but look at this from wikipedia:

All acetic acid bacteria are rod-shaped and obligate aerobes.[1] Acetic acid bacteria are airborne and are ubiquitous in nature. They are actively present in environments where ethanol is being formed as a product of the fermentation of sugars. They can be isolated from the nectar of flowers and from damaged fruit. Other good sources are fresh apple cider and unpasteurized beer that has not been filter sterilized. In these liquids, they grow as a surface film due to their aerobic nature and active motility. Fruit flies or vinegar eels are considered common vectors in the propagation of acetic acid bacteria.[2]

You'll need more than a rinse round with a bit of metabisuphite, but it's not cause for paranoic cleaning. Dilute bleach, unscrew taps and give the threads a bit of a seeing to with a toothbrush and then when eveything's ben soaked, use matabisulphite to kill the chlorine in the bleach. That pellicle you saw means they like to stay on the surface, indeed, they can't survive without air. This probably happpens to all of us at some time or another, especially with beers that are maturing in bulk and the air seal (airlock or whatever) has run dry.

Some styles, mainly Belgian, use acetic acid bacteria deliberately as part of a souring mix of bacteria. The important thing is to get it bottled up as soon as you detect infection. Once bottled, the beer's safe.
Click to expand...
I was kegging when I noticed - so sounds like it is ok. Thanks!!!
 
didoato said:
I was kegging when I noticed - so sounds like it is ok. Thanks!!!
Click to expand...

Hmm. The fact that "Acetic acid bacteria are airborne and are ubiquitous in nature," which is true, doesn't that imply that contamination that takes hold in a beer to the point that colonies can be seen with the naked eye is necessarily going to be ok. It might be. It might not. If this chalky stuff is indeed acetobacter, it has already made more acetic acid than a typical batch would contain. (Beer yeasts also make acetic acid, but usually not enough to be noticed as such.) The questions is, is it already above taste threshold, and/or will further production get it above threshold?

The vast majority of batches, like I dunno, 99.8% or so, are not contaminated, at least not noticeably. I emphasize this just so noone gets the impression that this is somehow normal, or that sanitation doesn't matter.
 
VikeMan said:
Hmm. The fact that "Acetic acid bacteria are airborne and are ubiquitous in nature," which is true, doesn't that imply that contamination that takes hold in a beer to the point that colonies can be seen with the naked eye is necessarily going to be ok. It might be. It might not. If this chalky stuff is indeed acetobacter, it has already made more acetic acid than a typical batch would contain. (Beer yeasts also make acetic acid, but usually not enough to be noticed as such.) The questions is, is it already above taste threshold, and/or will further production get it above threshold?

The vast majority of batches, like I dunno, 99.8% or so, are not contaminated, at least not noticeably. I emphasize this just so noone gets the impression that this is somehow normal, or that sanitation doesn't matter.
Click to expand...
I appreciate the additional info - thanks!
 
+1 to what @VikeMan said.^

That pellicle didn't grow overnight, and not all microorganisms grow pellicles. First the intruding spoiling vector needs to multiply enough to take over, competing with the yeast that's present. Some may produce a decent size pellicle, not all do. That pellicle then prevents other intruders from entering the liquid, so they remain top bug.

It's also difficult to point to a microorganism by looking at a pellicle. I'm therefore not convinced it's acetobacter per se.
 

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