Black spot on neck of yeast starter flask

[wepeeler]

So yeah, I made a lager starter on Sunday night. I went to harvest some last night, and I noticed a black spot on the neck of the flask. It's only on one side of the flask, so I decanted from the other side. The actual starter looks and smells completely fine, and I'm going to pitch it anyway, but I was wondering if any one has ever had this? It looks like the same black stuff that is sometimes in the krausen ring in the fermenter. It's not fuzzy, but it's black and slimy looking. (No pic, because I forgot to take one. I'll try to post one later.)

 

[GoeHaarden]

If it looks like krausen gunk, then it's probably krausen gunk.

Don't look so hard next time and you won't see it. Pitch away

 

[Brooothru]

Yeah, 99.9% chance of mold.

Might work fine. Might not. Is $8 really worth the risk of losing the whole batch if it's "not"? If so, roll the dice. Just remember Dirty Harry's question: "Are you feeling lucky?"

 

[wepeeler]

Update: black spot is gone. Starter smells and looks fine. Black spot turned to light brown. Almost looks like some DME dried and stuck to the neck. Weird. RDWHAHB. Brewing a German pilsner tomorrow!

 

[GoeHaarden]

Yeah, 99.9% chance of mold.

It takes several weeks for mold spores to colonize enough to be visible. Unless you didn't clean the vessel then visible mold would be highly unlikely in a starter...

 

[wepeeler]

It takes several weeks for mold spores to colonize enough to be visible. Unless you didn't clean the vessel then visible mold would be highly unlikely in a starter...

I cleaned the new 5L flask with PBW, then sprayed with Star San, then boiled. No chance it was contaminated. Just me being paranoid, I guess!

 

[Brooothru]

It takes several weeks for mold spores to colonize enough to be visible. Unless you didn't clean the vessel then visible mold would be highly unlikely in a starter...

That's odd. I opened a can of stewed tomatoes recently to use in some guacamole. Only needed about a quarter of the can, so I put the remainder in a Pyrex storage dish with locking lid immediately in a 38°F refrigerator. Five days later I went to incorporate it into a pasta sauce, but several large mold colonies had developed on the surface. Even with a fairly low pH, it took less than a week for spores to produce under normal food handling conditions.

A recent mold test kit I used in an RV recently after some water incursion damage produced several colonies within days as well on the petri dish media, though that was in open air conditions at around 45-50°F.

I don't think it takes several weeks. Just some airborne spores and a food source.

 

[IslandLizard]

Update: black spot is gone. Starter smells and looks fine. Black spot turned to light brown. Almost looks like some DME dried and stuck to the neck. Weird. RDWHAHB. Brewing a German pilsner tomorrow!

Maybe stop boiling wort in a flask and using a stainless steel cooking pot instead? They cool faster too in a sink or tub with cold water...

 

[GoeHaarden]

That's odd. I opened a can of stewed tomatoes recently to use in some guacamole. Only needed about a quarter of the can, so I put the remainder in a Pyrex storage dish with locking lid immediately in a 38°F refrigerator. Five days later I went to incorporate it into a pasta sauce, but several large mold colonies had developed on the surface. Even with a fairly low pH, it took less than a week for spores to produce under normal food handling conditions.

A recent mold test kit I used in an RV recently after some water incursion damage produced several colonies within days as well on the petri dish media, though that was in open air conditions at around 45-50°F.

I don't think it takes several weeks. Just some airborne spores and a food source.

Okay. I'm too tired for this. You're right, I'm wrong....

But I'm sure glad OP didn't dump his starter from your expert advise. No one would ever have beer to drink if we're telling them to dump without asking more questions or seeing a photo. Uninformed decisions are dangerous...

This place always turns into a measuring contest...

 

[Brooothru]

Okay. I'm too tired for this. You're right, I'm wrong....

But I'm sure glad OP didn't dump his starter from your expert advise. No one would ever have beer to drink if we're telling them to dump without asking more questions or seeing a photo. Uninformed decisions are dangerous...

This place always turns into a measuring contest...

Neither "measuring contest" nor expert advice. Just an observation based on anecdotal experience and a recommendation (O.P. did ask for advice) based on simple risk/reward analysis. If in doubt, is it worth $8.

Nothing more, nothing less.

 

[wepeeler]

Maybe stop boiling wort in a flask and using a stainless steel cooking pot instead? They cool faster too in a sink or tub with cold water...

I was actually going to start doing this in the future. I've read about flasks cracking on stovetops. (I use gas, not electric.) That's the last thing I need to deal with.