Fermentation vs. Clean-up

I've been tracking some various ideas on this website and have a couple of questions.

About a week ago, I did an American IPA kit. I replaced the Danstar Nottingham yeast in the kit with a SafAle US-05 (seemed more in line with the style, plus I've had great results with US-05). Fermentation went wild for several days then slowed down appreciably.

Now, the batch is still in primary and the blow off solution is still in place. Every couple of minutes I still get some bubbles.

My question is this: Is this still active fermentation or is it a by-product of the yeast cleaning up after itself?

Don't worry, I'm not in a hurry to rack it off; I'm just curious. I have an English Bitter in clearing right now, and it's not going anywhere until I have a keg free, then I'll rack the IPA into that carboy.

Anyway, I'm just curious, what exactly do people mean by the yeast "cleaning up after itself?" I think I've read that it produces a cleaner, clearer, better-tasting beer, but why? Is it taking proteins out of solution? Something else?

Thanks to anyone who can shed some light on this .

When the yeast run out of sugar to eat, they begin to metabolize ("eat") compounds they produced earlier in fermentation. This includes sulfur compounds, they turn fusel alcohols into esters, etc. After they finish with this, they go dormant. This is what is meant by "cleaning up".

As for your bubbles every few minutes... you really need to check the gravity. If the FG is about where you expected it to be, it's done... to really check this, you could check it a couple days from now and if it's still the same gravity, then you know it's done. Recently fermented beer also tends to have CO2 coming out of solution. So, if your beer is finished, that would explain your airlock bubbles.

Slow bubbles can also be due to a low-pressure weather system moving in.

I'll check the gravity when I rack to secondary. It'll be another week at least, so the yeast will have plenty of time to finish eating all of the sugar they want. I've never had a problem with US-05 attenuating properly, and since this batch has acted normally the whole way around, I'm not worried about it.

I'm assuming that allowing the yeast to keep working until they go dormant themselves is a good thing? That is, I want them to eat the compounds they produced, right? How long would it be until I have to worry about autolysis, if at all?

Thanks!

MBM30075 said:

How long would it be until I have to worry about autolysis, if at all?

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Under typical circumstances, it's a long wait for autolysis. However, depending on the temperature at which the beer is stored and depending on the beer style, decaying yeast cells and primary trub can cause off-flavors. This is more noticeable in cleaner beers (e.g., light lagers). The typical ale can sit on the primary yeast for 3 to 5 weeks w/o much problem though.