Endless fermentation

[dargaud]

Hello all,
I started making a light blonde (4deg circa) and left on vacation for 3 weeks. The temperature was 9C for the duration. When I came back it was still bubbling. I thought it would finish quickly once the temperature was raised in the house, but after 10 days at room temperature it was still bubbling healthily. Density was straight on 1000 so I bottled it, but I'm curious as to why it was still fermenting like that. What was going on ? Should I have left it till the (bitter?) end ?
Thanks

 

[J A]

What yeast were you using and how much? 9C is 48F and that's lager fermenation temps. It could take 3 weeks or more for a beer to finish at that temperature and it would require a big healthy pitch.
1.0 is very high percentage attenuation for beer yeasts. It's possible that you've picked up a wild yeast that's taking if further than it normally would go. Any off flavors? Anything odd about the appearance of the wort?
More info.

 

[Nosybear]

Density at 1.000 is a red flag - unless you used a lot of sugar in the wort or a very aggressive Belgian saison yeast, a final gravity that low is almost a sure sign of infection. As JA said, any off flavors, odors, odd looking yeast or stuff in the wort that doesn't belong?

 

[dargaud]

Density at 1.000 is a red flag - unless you used a lot of sugar in the wort or a very aggressive Belgian saison yeast, a final gravity that low is almost a sure sign of infection. As JA said, any off flavors, odors, odd looking yeast or stuff in the wort that doesn't belong?

Yuk... I didn't notice any smell. The taste was bland when I bottled it. It would be the 1st time I have an infection... I'll be careful when I open the 1st bottle !

 

[dargaud]

Well, I tasted the result recently and it's not bad at all. I'd dare say excellent even: slightly acidic which makes sense for such a long fermentation I guess, with a good head of foam.

 

[J A]

slightly acidic which makes sense for such a long fermentation I guess,

Only makes sense with a lactobacillus infection. You got yourself a little sour beer there.
Whatever equipment you used to ferment, transfer or store that batch in will likely be infected and you won't be able to get a clean beer out of it. Time to clean house and get rid of anything not glass or stainless.

 

[Hogarthe]

Only makes sense with a lactobacillus infection. You got yourself a little sour beer there.
Whatever equipment you used to ferment, transfer or store that batch in will likely be infected and you won't be able to get a clean beer out of it. Time to clean house and get rid of anything not glass or stainless.

I agree he probably got an infection but if the equipment is in good shape he should be able to sanitize it. Longer contact time with the sani than usual should work.

 

[HighVoltageMan!]

Well, I tasted the result recently and it's not bad at all. I'd dare say excellent even: slightly acidic which makes sense for such a long fermentation I guess, with a good head of foam.

Do you mean slightly tart? What yeast did you use? Certain yeasts will give that impression. Most lager yeasts are pretty good acid producers, especially if you used adjuncts or sugars for fermentables. Alt and Kolsch strains are even better at producing acid.

The easiest way to determine if the beer has an infection is by checking the pH. If you have a pH meter or know someone who does, you can check your pH. Lagers can go as low as 4.0, especially if they were made with adjuncts or sugars. Typical finish pH for a lager is 4.1-4.4. Alt yeast can go down to 3.9 and maybe even 3.8. But any lower than that, then as JA mentioned, it may be an infection.

Remember to remove the carbonation by passing it through a coffee filter before measuring the pH, the bubbles screw up the reading.

 

[HighVoltageMan!]

Longer contact time with the sani than usual should work.

That works, but if it's a tough infection, it may need a stronger sanitizer. If its glass or plastic, I would suggest a hot water bath with some bleach and white vinegar. 1 cup each, diluted in 5 gallons of hot soapy water. I love that stuff, it wipes out infections, even in plastic.

Boiling water works good for stainless.

 

[J A]

Typical finish pH for a lager is 4.1-4.4. Alt yeast can go down to 3.9 and maybe even 3.8.

Final gravity of 1.00 (assuming accurate reading) and flavor acidic enough to taste tart isn't normal yeast behaviour. A quick search for info on the subject indicates that pleasantly tart flavor starts in a PH range of 3.0 or so

 

[HighVoltageMan!]

Final gravity of 1.00 (assuming accurate reading) and flavor acidic enough to taste tart isn't normal yeast behaviour. A quick search for info on the subject indicates that pleasantly tart flavor starts in a PH range of 3.0 or so

I don't disagree with you, however 029 can produce a beer that is mildly tart in the finish. The pH of the beer is usually around 4 or so. If the finish is mildly tart and the pH is where it supposed to be then there's no problem, it's just a characteristic of the yeast. But if it gets as low as 3 as you say or even below 3.8, then you are correct to assume there is an infection. Typical beer that is infected is not only sour, but it has other nasty flavors as well. Since no off flavors were mentioned, it's possible it's not infected. The extended fermentation could have been a beer that finished fermenting, but hasn't finished de-gassing.

 

[J A]

The extended fermentation could have been a beer that finished fermenting, but hasn't finished de-gassing.

I'm still looking at the 1.00 final gravity piece of the puzzle. If that's an accurate gravity reading, it's not likely a clean fermentation.

 

[HighVoltageMan!]

I'm still looking at the 1.00 final gravity piece of the puzzle. If that's an accurate gravity reading, it's not likely a clean fermentation.

That is pretty low and you may be right. But if there is no off flavors other then the tartness, then it might be something else. Without further details, it's hard to know. Brut IPA's do go below 1.000 gravity, but it requires an active enzyme in the fermenter. I would love to try this beer just to see how it tastes.

 

[Mark Farrall]

9C is a bit cold for any of the acid producing bugs, even if you stumbled on one of the acid producing yeasts. Also lactobacillus struggles to drop gravity much. Half the strains don't at all and the other half only make a small change to gravity. So if it's there, it's only part of the picture.

I'd be guessing the gravity drop is more likely from a diastaticus sach or, less likely, a brett. They're the main culprits for a gravity that low. And if there was a bit of lacto, once you've got it back up to room temp it may have added some sourness, but they're a bit fickle and may not recover.

For the cleaning/sanitising it's the sacch diastaticus/brett you most have to worry about. Lacto is on everything and if you can't kill it off with your standard cleaning sanitising process then that's a bigger problem. Instructions above about a longer clean/sanitise make sense to me, unless it's older plastic. Older plastic may have cracks that time won't open up. They only open up when moving about (e.g. brewing).

 

[J A]

^^^ Good points.