Double kraeusen

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StrathclydeTaff
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Double kraeusen

Post by StrathclydeTaff » Thu Nov 14, 2019 12:46 pm

Something new and curious has happened with my fermenting wort for the second time in succession. In both cases, a standard and healthy looking kraeusen developed 24hrs after pitching yeast (but only 1" high), with a normal dark tide mark developing as it subsided. 36 hrs or so later an additional kraeusen grew above the original to produce a double layer but thicker than the original (~2" high). Temperature control is set at 20C in an insulated box using a standard 30l fermentation bucket for a 23l brew.
I'm brewing using mainly malt extract and crystal malt, with Whitelabs live yeasts. as per usual. The only difference with my last two brews compared to previous brews has been the use of Whitelabs Burton Ale Yeast with a tsp of gypsum (I've been using various other Whitelabs yeasts with good success for some time).
My first brew is a Special Bitter, fermentables being PME, Wheat ME and steeped crystal malt I got good attenuation with this: 1.055 down to 1.010 and it's been bottled for nearly two weeks so I've not yet tried it.
The current brew is made from PME and household sugar with steeped crystal malt and chocolate malt with an OG of 1.052. This has just developed its secondary kraeusen 4 days after pitching yeast.
I assume it's something to do with phased metabolism of the fermentables but I've not seen or read anything like this before if anyone has a specific explanation then I'm all ears.
cheers
ST

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Re: Double kraeusen

Post by Top Cat » Thu Nov 14, 2019 6:43 pm

It’s more common than you think!
I’ve had exactly the same problem inconsistently for the last 18 months using dried yeast (us 05) and yeast scrounged from St Austell Proper Job.
In some instances the krausen went through the air lock on it’s increase. To counter the problem I unclip the lid on the fermentation bin when fermentation is underway, then replace it after about 4 days.
I have temperature control with an inkbird at around 18c.
I am also all ears to an explanation too!!!

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Re: Double kraeusen

Post by IPA » Fri Nov 15, 2019 9:07 am

Top Cat wrote:
Thu Nov 14, 2019 6:43 pm
It’s more common than you think!
I’ve had exactly the same problem inconsistently for the last 18 months using dried yeast (us 05) and yeast scrounged from St Austell Proper Job.
In some instances the krausen went through the air lock on it’s increase. To counter the problem I unclip the lid on the fermentation bin when fermentation is underway, then replace it after about 4 days.
I have temperature control with an inkbird at around 18c.
I am also all ears to an explanation too!!!
I have a suspicion that some yeast strains,the ones that try to climb out of the FV, do so because,like drowning humans, they are seeking oxygen in order to multiply rather than produce alcohol. That could be why when you loosen the lid the krausen subsides. No proof but just a strong conviction. I always loosen or remove the lid once the fermentation is under way.Some brewers prefer to beat the yeast back down into the fermenting wort. Also I have not used an airlock in years. I use foam bungs which exclude bacteria but allow the passage of oxygen and can remain in place during transfer.
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Re: Double kraeusen

Post by McMullan » Fri Nov 15, 2019 7:45 pm

Sounds like a yeast issue to me. Luckily they recovered and got back to work. Did you make a starter ST?

StrathclydeTaff
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Re: Double kraeusen

Post by StrathclydeTaff » Sat Nov 16, 2019 6:22 pm

Yes - I usually do a yeast starter even with live yeast to confirm they are ok. This was active for two days then stopped bubbling through the airlock. I then stored it in the fridge for a day before pitching.

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Re: Double kraeusen

Post by McMullan » Mon Nov 18, 2019 8:59 am

For primary activity to get interrupted like you describe something probably spooked the yeast. A sharp drop in temperature overnight, for instance. Because of the timing, though, I’d guess it’s a stress response to the CO2 level building up, due to an airlock being used. Even the slightest pressure, such as promoted by an airlock, is sufficient to promote a significant increase in dissolved CO2. It’s not simply associated with temperature. Pressure has an effect too. Some strains are more sensitive than others. I’m not familiar with WL Burton Ale, but I suspect it’s sensitive to the build up of CO2. Try fermenting without an airlock, as ‘IPA’ suggests. It’s good practice not to use an airlock during primary fermentation. Obviously, use one when it’s done. Yeast are adapted to survive on surfaces (tree bark, leaves, fruit, etc.) exposed to air. This is why it pays to aerate the sweet wort well. The yeast cell’s defence response (to toxic O2) is to multiply, under favourable wort conditions, which is exactly what brewers want them to do.

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Re: Double kraeusen

Post by StrathclydeTaff » Mon Nov 18, 2019 1:12 pm

Thanks for that advice - I'll omit the airlock initially next time I try using Burton Ale yeast. Temperature is constant - I've filled a thermostat to a small laboratory hotplate and everything sits inside a box made of 15cm thick Kingspan insulation. The wort was initially well aerated - poured into a 25l bucket fitted with a tap and then flowed slowly through the tap on to an upturned bowl resting on a sieve at the top of the fermentation bucket.
Oddly, although I've fitted an airlock, the fluid inside remains balanced throughout all the kraeusen build-up with no bubbling during the primary fermentation (23l brew in a 30l bucket). The lid seems to fit very well but maybe there is leakage somewhere.

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Re: Double kraeusen

Post by Kev888 » Mon Nov 18, 2019 1:48 pm

I've only used the Burton ale yeast a couple of times, but FWIW have no recollection of a temporary drop in its krausen, so this doesn't seem entirely normal to me.

So yes, as above, omit the airlock for traditional styles of ale yeast whilst they are producing plentiful CO2, and they will likely be a little happier. I do like to use an airlock once they die down though.

Also, if not already done so, it could be worth checking that the wort (e.g. not just the chamber) does actually stay roughly at the desired temperature. In some cases control systems can over-react to the fermentation's heat and turn off the warmth for too long, or not react enough (or at all) and allow the wort to get too warm during the vigorous stage, consequently with a drop in temperature as activity begins to slow.

One other slight possibility is that the FV may have started venting/leaking more as time went on. That could cause the krausen to initially relax a bit even if the yeast weren't struggling, and possibly then re-appear due to renewed activity (from when the yeast sank back down into the wort, and perhaps also began to find it easier to vent CO2).
Kev

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Re: Double kraeusen

Post by StrathclydeTaff » Mon Nov 18, 2019 6:57 pm

Thanks for these comments and suggestions. It might be worthwhile fitting a thermometer to sit in the wort and use those readings as a basis for setting the air chamber/thermostat temperature. I've always assumed that the air and wort temps may deviate due to the yeast activity but fermentation has generally worked ok using a air chamber temp of 20C and this double kraeusen has only appeared on the two occasions I've used the Burton Ale yeast.

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Re: Double kraeusen

Post by IPA » Tue Nov 19, 2019 8:18 am

StrathclydeTaff wrote:
Mon Nov 18, 2019 6:57 pm
Thanks for these comments and suggestions. It might be worthwhile fitting a thermometer to sit in the wort and use those readings as a basis for setting the air chamber/thermostat temperature. I've always assumed that the air and wort temps may deviate due to the yeast activity but fermentation has generally worked ok using a air chamber temp of 20C and this double kraeusen has only appeared on the two occasions I've used the Burton Ale yeast.
Buy a thermowell from The Malt Miller and fit it to your FV. Then you can measure the exact temperature of the fermenting wort.
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Re: Double kraeusen

Post by Kev888 » Tue Nov 19, 2019 11:30 am

StrathclydeTaff wrote:
Mon Nov 18, 2019 6:57 pm
Thanks for these comments and suggestions. It might be worthwhile fitting a thermometer to sit in the wort and use those readings as a basis for setting the air chamber/thermostat temperature. I've always assumed that the air and wort temps may deviate due to the yeast activity but fermentation has generally worked ok using a air chamber temp of 20C and this double kraeusen has only appeared on the two occasions I've used the Burton Ale yeast.
Yes, if you haven't done so before then it could be well worth checking on how the temperature of the wort itself differs from what you wished during the vigorous part of the fermentation. It may be fine and the break in krausen due to something else entirely, like pressure. But if things conspire against you then it could easily become several degrees out, so it would be useful to know - even if just to eliminate as a cause.

Whatever the cause, it isn't entirely surprising that some yeast may be more affected than others. Some will try to work at faster rates and produce more heat than others, and/or can be more sensitive to temperature (amongst other things) too. Some will also climb more readily into the krausen if it is permitted to get big enough, reducing numbers in the wort - keeping a cap on the temperature and allowing the CO2 to freely escape may be more important than for other types.

Unfortunately I've not used the Burton ale yeast enough to know the characteristics. So not sure if any of these things are more or less likely in this particular case.
Kev

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Re: Double kraeusen

Post by StrathclydeTaff » Thu Nov 21, 2019 1:12 pm

Many thanks for these are good suggestions that I'll follow for future brews: omit the airlock until krauesen has peaked (I am the only one to spell it this way? - taken from Palmers excellent book published in USA) and fit a wort thermometer to compare to ambient and control ambient accordingly.
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Re: Double kraeusen

Post by McMullan » Thu Nov 21, 2019 2:50 pm

A thermowell (temp control probe) in the wort is definitely worthwhile. You'll be shocked how much higher than ambient the wort temp can be during active primary. It's amazing how much heat the yeast kick out.

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