Possible infection

[BackToBasics]

I've had a kolsch fermenting at 17°c for the past 10 days. Haven't really paid a huge amount of attention to it until today. Only checked on it today as I'm starting ramping the temperature up over the next few days before cold crashing/lagering.

I do know that the krausen dropped after day 3 or 4 but there is still some foamy stuff on the surface now. Doesn't look like krausen - it looks a a bit "scummy" in places. I'm not about to dump it but I'm a little concerned that I've got an infected batch.

Everything was cleaned and sterilised as normal. The only difference to my normal process was that I wasn't confident that my yeast starter was ready for pitching so the wort sat in the fermenter for 24 hours before pitching.

What are the chances I have a ruined brew?

 

[smcc]

I would say its possible but until you take a sample and smell and taste it you wont know. There are a lot of people who dont have proper cooling capability so basically store hot wort in cubes overnight, as long as it was sanitised and sealed it should be ok. Take a sample and see really

Or if you know someone with microscope it can be plated and you will see (long rods typically mean bacteria) tiny dots can be wild yeasts.

 

[Clint]

Post us a piccy!

 

[BackToBasics]

Taken a sample and other than it fermenting lower than I expected it seems okay. Just smelt boozy and tasted clean and slightly malty.

Picture was taken after I took the sample so it's disturbed the foam a bit - does seem to have lost some of the scummy appearance though.

Think it's probably okay but I'll be keeping a closer eye on it now.

 

[Clint]

Looks fine!

 

[Covrich]

probably last bit of krausen yeast foam and just co2 it looks perfectly healthy to me

As they often say RDWHAHB (well maybe not at 9:55am)

 

[BackToBasics]

Just to follow up on this, while it may not have been an infection something went wrong with this beer.

Despite 4 weeks of lagering and a few weeks in the keg it's still very hazy and, more annoyingly, there's a distinct off flavour - I'd say bananas. It's drinkable but a far cry from what I was expecting. Don't really want to dump it but the thought of drinking a full keg of it isn't appealling.

 

[trevorS]

the thought of drinking a full keg of it isn't appealling.

Then don't!

 

[Wynne]

Just to follow up on this, while it may not have been an infection something went wrong with this beer.

Despite 4 weeks of lagering and a few weeks in the keg it's still very hazy and, more annoyingly, there's a distinct off flavour - I'd say bananas. It's drinkable but a far cry from what I was expecting. Don't really want to dump it but the thought of drinking a full keg of it isn't appealling.

That’s probably from an ester called isoamyl acetate, produced by certain yeast strains, particularly wheat beer strains. Ester production during fermentation increases with fermentation temperature. What yeast did you use? Was 17C the temperature of the fermenting brew or the temperature inside the fridge? If it was the fridge, the brew itself could have been warmer at times.

 

[cushyno]

Kölsch yeast can be a bit fruity depending on the brand/strain.

When you made the starter, what temperature was that at, and did you pitch the whole starter in or decant off the supernatant first?

Pitching temperature can have an effect on ester production, so even though you fermented at 17 °C, if there yeast was pitched warm, or there was a temperature difference between yeast and wort of more that a couple of degrees, that can stress the yeast and cause esters.

Did you do anything unusual to the mash such as adding more grain part way through the mash? Theoretically it's also possible to induce greater banana esters through a decoction at 62°C recombined with a mash that has been at 38°C, before heating back to 62°C for the usual sach rest. You probably didn't do this, but just saying it's possible with some yeasts to give the right conditions during mashing to induce isoamyl acetate, regardless of fermenting temperature.

 

[BackToBasics]

Nothing unusual about the mash. All grain at start (90% pilsner, 7% carapils, 3% wheat), 60 mins at 65°c, 10 mins at 75°c. Not that it matters but it's a David Heath recipe.

Fermentation temp was based on an inkbird probe attached to the side of the vessel. It was fairly well insulated (several layers of kitchen paper secured with duct tape) so I think it should be fairly close to wort temp. Temperature was ramped up to 20°c for a few days at the end.

Yeast was lallemand's kolsch. A quick Google doesn't suggest anyone else having such a distinctive banana flavour though. It's probably highly unlikely, but I did wonder if it was actually their wheat strain in the pack. Lallemand's flavour profile for their kolsch gives a 0/5 for banana flavour the wheat is a 4/5.

Notes about the starter are interesting. No temp control, just left on the side in the kitchen on the stir plate. This was before it got warm though - ambient temp in there is usually around 18°c. Full starter was pitched - I've never bothered decanting.

I think kolsch should be a style I like (never had a commercial one) so I'm disappointed with the result.

 

[Wynne]

Nothing unusual about the mash. All grain at start (90% pilsner, 7% carapils, 3% wheat), 60 mins at 65°c, 10 mins at 75°c. Not that it matters but it's a David Heath recipe.

Fermentation temp was based on an inkbird probe attached to the side of the vessel. It was fairly well insulated (several layers of kitchen paper secured with duct tape) so I think it should be fairly close to wort temp. Temperature was ramped up to 20°c for a few days at the end.

Yeast was lallemand's kolsch. A quick Google doesn't suggest anyone else having such a distinctive banana flavour though. It's probably highly unlikely, but I did wonder if it was actually their wheat strain in the pack. Lallemand's flavour profile for their kolsch gives a 0/5 for banana flavour the wheat is a 4/5.

Notes about the starter are interesting. No temp control, just left on the side in the kitchen on the stir plate. This was before it got warm though - ambient temp in there is usually around 18°c. Full starter was pitched - I've never bothered decanting.

I think kolsch should be a style I like (never had a commercial one) so I'm disappointed with the result.

A couple of further thoughts.

Given the 0/5 banana rating, it may be worth reporting the problem to Lallemand in case it correlates with other complaints or known production issues.

I note that you made a starter, this is not required/ desirable when pitching dried yeast at the recommended dosage. During the growth phase in a starter, the sterol content of the individual cells, which is optimal dried yeast is depleted by making new cell walls with the result that the yeast vitality is reduced or exhasted by the time it is pitched which makes oxygenation of the wort more critical. If using the correct dosage of dried yeast for your wort concentration/volume you may be overpitching. However, over production of esters is more consistent with yeast stress from under-pitching.

Personally, I would take it a step at a time and see what response you get from Lallemand first. If you try another Kolsch using dried yeast, rehydrate it in accordance with the maker’s recommendations and pitch the rehydrated yeast at the recommended dosage rather than building cell count via a starter.

Please post how you get on, good luck!

 

[BackToBasics]

I don't usually use a starter for dried yeast. I only did one here as I'd ordered the kolsch yeast based on lallemand's pitch rate for their verdant strain. Turned out the kolsch needed nearly twice as much so, rather than delay the brew day, I made up the starter.

I'll be honest though - I didn't know there was an issue with starters made using dried yeast. I realised it wasn't very common but the usual answer for why this is was that dried yeast is cheap enough to just buy extra and not bother with a starter.

I will try another kolsch but maybe a smaller batch next time the mini keg is empty.