Beer seems to start fermenting again

I have had my batch of beer in primary for two weeks. Fermentation started great a was done with in the first week. I went to check on it a week later, day before bottling, and there was airlock activity. I took of the top to take a hydrometer reading and there was bubbling foam on the top of the beer. Any one ever heard of beer starting to ferment again? I took a hydrometer reading and it has not changed in the week. Should I proceed to bottling? Or wait. I thought there might have been contamination but the beer tastes fine, maybe a little sweet. It smells almost like pineapple juice, is the best I could describe it.

If it's a little sweet -- that makes me think it's got more to go. The more fermented it is, typically the dryer (less sweet), it should taste. The pineapple juice is throwing me off-- could be citrus hops.

Do you have gravity readings?

To answer the principles behind the question though: yes, this it is very possible that fermentation stalled and restarted. This is usually caused by a temperature drop/rise outside of the range that the yeast can handle so they shut down, when the temperature gets back to their comfort zone again, they come out of "hibernation"

Yes my hydrometer reading is 1.012. The recipe I purchased said the fg should be between 1.011 and 1.014. The temperature has stayed between 70 and 75 degrees. The hops I used were cascade.

hmmm, Well, I've never had a full out infection myself -- hopefully that's not the case here....it'd be one badass infection if it was brewing a krausen.

Because you are bottling, you really don't have a choice -- you need to wait until whatever is going on in there is over. If you were to put that stuff in bottles, you could have potential bottle bombs.

If it is 1.012 and your terminal gravity was supposed to be 1.011, it's possible that it may just be cleaning up that last few bits.

If it were me, I'd let it sit another week and take a peek every day to see what's going on. After a week the fermentables will have to be exhausted (or your hydrometer is busted). Then I would taste it to see if it had soured or gone nasty from wild yeast -- if not, you are good to bottle. If it is nasty, time to dump it. Unfortunately, in a situation like this, your only option is patience.

That's what I was thinking. I was thinking about kegging instead of bottling.

f4an said:

That's what I was thinking. I was thinking about kegging instead of bottling.

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If you were keg it, I'd still probably recommend waiting to see what was happening. But if you thought that it was a fluke, you wouldn't have the risk of bottle bombs to worry about.

The one other option you could look into is running to the LHBS and picking up some critters and make it a sour beer and hope the critters you introduce beat out the wild yeast. I still like the original plan of just waiting it out though -- if it is infected, look at your process and see how it could've happened.

i tasted some today and it tastes fine. No more activity. Not too sure. Just going to proceed tomorrow as if it went as normal. It is my first all grain batch. Maybe the hops had to settle out a little more and the yeast started again?? Thanks for your help.

f4an said:

I have had my batch of beer in primary for two weeks. Fermentation started great a was done with in the first week. I went to check on it a week later, day before bottling, and there was airlock activity. I took of the top to take a hydrometer reading and there was bubbling foam on the top of the beer. Any one ever heard of beer starting to ferment again? I took a hydrometer reading and it has not changed in the week. Should I proceed to bottling? Or wait. I thought there might have been contamination but the beer tastes fine, maybe a little sweet. It smells almost like pineapple juice, is the best I could describe it.

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What you are observing is probably just some of the residual dissolved CO2 coming out of solution due to a slight temperature change or other disturbance. This is very common when racking the beer to a secondary. You put the airlock back on and it starts bubbling again even long after it has finished out. No change in the hydrometer reading indicates that it's done. I say go ahead and bottle it up immediately. You're worrying too much and you know what that can lead to!:cross: