FV surface layer - mould or wild yeast bacteria?

[Mj711]

Hi all

I’ve had a couple of brews sitting in the fermenters while I was away on holidays. Fermentation started 4 April and each finished around 20 April. Before I left I’d dumped the trub, removed the spent dry hop bags, and set both FV’s to maintain 6 deg to kill fermentation while I was away. Fast forward 3 weeks (today) as I’m transferring to kegs, I’ve noticed one of the brews with a white mould like surface layer. The other brew is fine.

The brew in question was kettle soured with helveticus (wild yeasts are still relatively new to me). I’ve never seen this before and wondering if this layer on top could be the wild bacteria or something funkier. It smells sour and only seems to be on top (not visibly suspended in solution).

I’ve attached pics and would really appreciate your help in trying to figure this one out!

Ps. the yellow floaty is just my rapt pill.

Cheers
Matt

 

[Miraculix]

Yes that's an infection. Removing something from the fermenter and then letting it sit is a bad idea. If you remove something, you automatically get air inside. With the air comes oxygen so even if you wouldn't have an infection, you would have oxidised beer by now.

Good thing is, maybe the infection prevented the oxidation. Give it a try, how does it taste? Maybe worth keeping? Beware of bottle bombs though.

 

[Mj711]

Hi Miraculix

I’d kept it in the same vessel throughout the process (GF conical). After opening to remove the hops I’d purged with co2, although the lid’s seal isn’t air tight so some oxygen has undoubtedly found it’s way inside. I’ve kegged it for conditioning so will wait and see 🤞🏽

It tastes good! I was more worried about getting sick from bad bacteria, but I’m guessing the alcohol would kill it off anyway?

Cheers
Matt

 

[Miraculix]

Hi Miraculix

I’d kept it in the same vessel throughout the process (GF conical). After opening to remove the hops I’d purged with co2, although the lid’s seal isn’t air tight so some oxygen has undoubtedly found it’s way inside. I’ve kegged it for conditioning so will wait and see 🤞🏽

It tastes good! I was more worried about getting sick from bad bacteria, but I’m guessing the alcohol would kill it off anyway?

Cheers
Matt

Don't worry, the pH, alcohol and absence of oxygen is taking care of the really nasty things. Only problem is when you keg this one, you would probably want to change the lines afterwards as you probably won't get them really clean again afterwards. Good chance that the infection will stay in your system that way.

 

[IslandLizard]

What @Miraculix said!^
BTW, it's not mold, it's called a pellicle. Some micro-organisms create pellicles in their quest to keep intruders out. The pellicles are totally harmless, but you do have an infection in your beer that could affect taste, aroma, and may make your beer sour.

 

[Mj711]

Thanks @Miraculix and @IslandLizard! Will be sure to keep this as the pellicle line for the next next encounter 😉

 

[IslandLizard]

Just reread your OP:

The brew in question was kettle soured with helveticus (wild yeasts are still relatively new to me).

My emphasis.^
Did you re-pasteurize (by heating) the beer after the souring organism(s) did their work? That's often done with kettle sours. If not, that could explain the pellicle. Although from what I understand, yeasts don't create pellicles, only bacteria do.

This may explain that, from Lallemand:
"WildBrew Helveticus Pitch™ is a high-performance, high-purity lactic acid bacteria [...]"
https://www.lallemandbrewing.com/en/canada/product-details/wildbrew-helveticus-pitch/

 

[Miraculix]

Just reread your OP:

My emphasis.^
Did you re-pasteurize (by heating) the beer after the souring organism(s) did their work? That's often done with kettle sours. If not, that could explain the pellicle. Although from what I understand, yeasts don't create pellicles, only bacteria do.

This may explain that, from Lallemand:
"WildBrew Helveticus Pitch™ is a high-performance, high-purity lactic acid bacteria [...]"
https://www.lallemandbrewing.com/en/canada/product-details/wildbrew-helveticus-pitch/

Brett can create pellicles as well and they are yeasts.

 

[IslandLizard]

Brett can create pellicles as well and they are yeasts.

Yes, of course! Thanks for the correction.

Good, semi-scholarly read on pellicles here:
https://phdinbeer.com/2015/01/30/beer-microbiology-what-is-a-pellicle/

 

[IslandLizard]

Only problem is when you keg this one, you would probably want to change the lines afterwards as you probably won't get them really clean again afterwards. Good chance that the infection will stay in your system that way.

Not necessarily needed to change the lines, but it does require thorough cleaning and sanitizing of everything that has come in contact with the infected beer.

Recirculating strong, hot (homemade) PBW/Oxiclean, reinforced with some Lye (NaOH) comes to mind, as well as cleaning every nook and cranny the infection vector can hide in, such as valves, connectors, hoses, canes, etc. Any biofilm needs to get removed/obliterated.

 

[JAReeves]

If it tastes good, try to save about a pint of it including a bit of pellicle and whatever falls to the bottom of the tank. Then you can infect another batch and get similar results. The percentage of the various wild yeasts/bacteria will vary in every batch, but you should be able to get somewhat consistent results. I have been using the same sour culture for about 6 years now, harvested from our grapes. It's a winner, and I am learning to control certain parts of it for consistency.