Exploding Bottles. Fermentation not complete, earlier yeast or something wild?

[Luxo_Aussie]

G'day All,

I've been cleaning up several bottles which have exploded in my cellar. The cause was 3 things which together has pushed this batch over the edge:
1) Over-priming, not adjusting for dissolved C02 when bottling at 6deg)
2) Heatwave, cellar reached 22 degrees
3) Continued fermentation after bottling, bottled at 1018 -> 1005 today
(to be fair, the bottles handled an epic amount of pressure before finally subcomming!)

#3 has me amazed. For this batch I used Scottish Ale 1728, 1.5L starter, yeast nutrient, controlled fermentation in stainless, ramp to 22 degrees to ensure full ferment (+checked with TILT Pro) and cold crashing before bottling. Attenuation was 71%. Short of oxygenating the batch before pitching (I'll do that next time), there's not much more I could have done to prevent this from happening, which leaves me asking what could have caused it.

There was consistent over-carbonation with no off flavours here which leads me to think it's not an infection. It's worth noting that this is not my only batch where this has happened, I have a Marzen which was bottled at 1012 and is now 1006. Lastly, there could be tiny particles of Trappist High Gravity 3787 stuck in my bottling device/tubing which then got into my bottles to then ferment it down further, but on a consistent level after sanitizing? Maybe a few bottles but not every single one to the same point.

Logically it's poor yeast health leading to incomplete ferment, wild yeast which provides no taste change or a prior yeast stuck in my bottling equipment - any thoughts on what might have caused this continued fermentation?

Cheers!

 

[Simon N]

Sorry to hear that. Only time I’ve had trouble was when the previous batch used diastaticus yeast. I’d put my money on that or an infection as that’s a pretty significant drop in gravity. What was the OG and how long had you let if ferment?

 

[Luxo_Aussie]

Sorry to hear that. Only time I’ve had trouble was when the previous batch used diastaticus yeast. I’d put my money on that or an infection as that’s a pretty significant drop in gravity. What was the OG and how long had you let if ferment?

Thanks for replying, OG was 1062, style was a export stout. Ferment was around three weeks; 5 days at 18 degrees (until it got to 1020) then raising a degree or so per day until 22 degrees at which point I held it for 5 days here to make sure it was complete + roused it twice to make sure before crashing down to 6 degrees for another week. I was super concerned about the 1018 FG, but I'd mashed high ~68 & the yeast wasn't a super attenuator so thought it was just the style.

 

[Grmblz]

Just one of many possibilities: Hop Creep: Causes, Effects and Prevention - Precision Fermentation.

 

[Luxo_Aussie]

Just one of many possibilities: Hop Creep: Causes, Effects and Prevention - Precision Fermentation.

Thanks for the reply, however this batch wasn't dry hopped with mostly bittering and some flavouring hops at 10min.

 

[golfandbrew]

You sure something isn't off with your Tilt. Did I miss that you are checking double checking your Tilt gravities with a hydrometer.

 

[Luxo_Aussie]

You sure something isn't off with your Tilt. Did I miss that you are checking double checking your Tilt gravities with a hydrometer.

I'm double checking with my Hydrometer, even after years of use and calibrating the TILT can always be off by a few points. Great tool, but wouldn't trust it for a FG reading

 

[akx]

Maybe an obvious question, but did you degas the sample? Is it definitely 1.005? I'm trying to do the maths and I think an extra 13 gravity points (1.018->1.005) is an extra ~6.5 vols of CO2 (on top of co2 in solution)... that seems wild.

 

[Luxo_Aussie]

Maybe an obvious question, but did you degas the sample? Is it definitely 1.005? I'm trying to do the maths and I think an extra 13 gravity points (1.018->1.005) is an extra ~6.5 vols of CO2 (on top of co2 in solution)... that seems wild.

Super valid question, I've actually noted this difference before when testing post-bottling. To be sure for this batch I left it overnight to make sure it had fully decarbed.
The bottles did an incredible job to last 7 months as I over primed as well (didn't account for dissolved C02) so it was more like an extra 6.5 on top of the 3.6 (1.4 dissolved, 2.2 from priming) I got from bottling.

 

[Luxo_Aussie]

While the above sounds like a bad situation, imagine every second bottle in your cellar of 600 is affected.

I've been testing most of my batches and half seem to be affected with them gushing or being super over-carbonated. Most were bottled in the 1011-1014 range but are now consistently showing 1004-1005 but none have any off flavours. Whatever has happened is very consistent at least but now it's hard to know when to bottle as this could just keep happening. The latest one was a Belgian single with 3787 bottled in mid-June at 1012, now its 1004 after just two months. I'll re-bottle each of these batches to solve the problem, massive PITA.

I'm taking my time with most of these batches, fermenting for plenty of time ramping 11->22 for Lagers (4 weeks) and 18->23 for ales (2 weeks). Yeast pitch is always more than it should be, fermentation is in line with attenuation estimates, so logically it HAS to be something at bottling..? Or could this be anything else?

 

[Half-baked]

My money is on diastaticus, sounds exactly like my experience a few years ago. You’re still in Lux, right so it’s pretty warm at the moment?

Diastaticus only needs a few cells and will be dormant in colder temps, but takes off under warmer conditions. Has no off flavour but strips out some of the malt flavour.

Probably an infection at bottling, but as it only takes a few cells it could possibly be earlier in the process.

My advice is to heat treat (lots of boiling water with a decent contact time) everything you can and replace whatever you can’t. Massive pita but it was totally worth it for me, haven’t had a problem since (have also avoided sta-positive yeast subsequently).

 

[Markbeer]

It would be impossible to re-bottle wouldn't it?

You just need to open the caps a touch and vent until it's okay.

Can be dangerous. Gloves and eye protection.

 

[MHB]

Diastaticus or another highly attenuateive wild yeast really does sound like the best possibility.
People in fruit growing areas (especially wine, apples, pears...) often find there is a lot of wild yeast in the air around certain times of the year. Might be interesting to look at when the over attenuating batches were brewed/bottled. I knew one brewer who had to take a break from brewing for a couple of months a year for very similar reasons to those you are experiencing.

You could possibly pasteurise the bottled beer once you have the condition you want, generally heating to 50oC will kill most yeast without doing too much to the flavour of the beer, do a bit of googling.
Mark

 

[Luxo_Aussie]

It would be impossible to re-bottle wouldn't it?

You just need to open the caps a touch and vent until it's okay.

Can be dangerous. Gloves and eye protection.

Not impossible, I've done it once before - Opened every bottle, poured into a bottling bucket and allowed to decarb. After 48hrs added priming sugar and re-bottled. It wasn't hoppy and rather strong (9.7% Triple) so probably was more forgiving than some other ones which wouldn't like the extra oxygen.

I did try the open-vent-cap-repeat technique and after 7 rounds it still wasn't working so gave up and just re-bottled.

 

[Luxo_Aussie]

Diastaticus or another highly attenuateive wild yeast really does sound like the best possibility.
People in fruit growing areas (especially wine, apples, pears...) often find there is a lot of wild yeast in the air around certain times of the year. Might be interesting to look at when the over attenuating batches were brewed/bottled. I knew one brewer who had to take a break from brewing for a couple of months a year for very similar reasons to those you are experiencing.

You could possibly pasteurise the bottled beer once you have the condition you want, generally heating to 50oC will kill most yeast without doing too much to the flavour of the beer, do a bit of googling.
Mark

On investigation its more or less every batch for the past year, with some exceptions around those which already attenuated fully or those where I used CBC-01, that yeast won't allow much else to grow!
I think the cause has been unclean (from parodic tastings) tap curved end piece on the Grainfather Conical after being exposed to the damp cellar. With that fixed and the cellar bleached let's see how things go moving forward.