Over Attenuation...a thought about prevention

[hops2it]

2 weeks into fermentation on a batch of Yoopers Dead Guy clone (AG) and I still have airlock activity which sort of surprised me to be honest. I'm not necessarily looking a gift horse in the mouth but it got me thinking...do any of you that tend to do long primaries ever check sg at 2 weeks just to make sure you're not already at your expected fg? I mean is there such a thing as preventative maintenance against potential over attenuation?

I ask this mainly because Beersmith recommended 2 pks S-05 dry pitch and that's the first time I've added 2 pks of that yeast. It tends to get right after it in my experience so I have this nagging thought of overdoing it.

And if anyone has ever done this, would moving to cold crash stop the process if I've already reached or exceeded the target fg? Would there be any downside to force stopping it in that instance?

 

[iambeer]

Did you take two gravity readings a few days apart lately see if there's a change in gravity?

 

[pjj2ba]

Changes in temperature can also cause bubbles in the airlock, so that is not a safe way to judge if a beer is done. Most beers actually ferment much quicker than people think. 3-7 is pretty normal. After that the sugars are gone and the yeast are just cleaning up any fermentation byproducts.

I don't know if there is a really good way to control attenuation once it is fermenting. The biggest controls for attenuation are your grain bill and how you mash (and choice of yeast). The amount of yeast you pitch and the temperature you ferment at can have an impact (more and warmer giving higher attenuation), but these are dwarfed by the other determining factor. Eventually the yeast will chug through all of the sugars it can metabolize, whether it does it in the fermentor, or in the bottle/keg. The danger is of course bottle bombs

 

[Pilgarlic]

I've always thought that the term "targeted" final gravity confuses some. Once it's in the fermentor, your objective is to have the yeast finish, that is, metabolize all the fermentable sugars and clean up the waste. Depending upon everything that happened BEFORE you put it into the fermentor, the ending gravity may be higher or lower than what the recipe suggests, but, generally, you should make no effort to control that in the fermentor other than seeing that the fermentation doesn't stall, but consumes all the fermentable sugars. The sugars measured in the final gravity should be the unfermentable sugars that lend your beer body, some maltiness and a wee bit of sweetness (these sugars aren't very sweet). By the way, doubling your yeast pitch won't change the ratio of fermentables to unfermentables and shouldn't effect your FG at all, though it may change how the yeast reproduce and thus will change the character of the beer.

 

[hops2it]

By the way, doubling your yeast pitch won't change the ratio of fermentables to unfermentables and shouldn't effect your FG at all, though it may change how the yeast reproduce and thus will change the character of the beer.

Yeah I only did that because it was calculated that 225 B cells were needed for this grain bill and the viable cells per pack of US-05 is 140 B. So I just put some faith into those numbers and pitched the extra pack.

I haven't taken a gravity reading yet (other than OG which was fine) and I'm fermenting at a rather precise 64-65 degrees in the fermentation chamber with the probe taped in platic wrap on the outside of the bucket like I normally do. I did mash slightly lower than the recipe called for due to an error on my part. Ended up at about 153-154 instead of 157 but I didn't figure that'd be enough variance to cause a huge difference in terms of available sugars.

Anyway, I was just kind of surprised to the activity this late in the game with tight temp control but it's probably fine. I may check the sg sometime this next week and see what's up.

 

[Pilgarlic]

So what I hear you saying is that the mash was at 153-154 at the end of the mash. What about between then and the boil? Did it drop further as you ran off into the kettle? Did it drop in the kettle before you fired it up? Before I began to mashout I was consistently overattenuating and it was because I might finish my mash near my target mash temp, but wouldn't denature the enzymes by raising the temp at the end of the mash, and running off into a kettle on the burner with the fire on. The mash temp finished right, but the runnings dropped in temp into the kettle and dropped further while I accumulated the runnings before firing up. All of that time conversion was continuing at lower temps that allowed the beta amylase to do its work, diminishing my unfermentables and yielding a more attenuative wort. Not sure if this may be your issue, but hope it helps. Review mashout procedure and turn on your gas or heat to your kettle once you've gathered an inch or so of runnings.

 

[Pilgarlic]

None of this, however, may apply at all if all you're seeing is continued bubbling, which may mean nothing at all. A more attenuative wort may not even translate at all into a longer fermentation, just a lower FG.

 

[homebrewdad]

Bubbling a long time means nada. This could be degassing, changes in temperature, berometric pressure, etc.

The only way to know if you are getting extended fermentation/overattenuation is to take hydrometer readings.

 

[hops2it]

So what I hear you saying is that the mash was at 153-154 at the end of the mash. What about between then and the boil? Did it drop further as you ran off into the kettle? Did it drop in the kettle before you fired it up? Before I began to mashout I was consistently overattenuating and it was because I might finish my mash near my target mash temp, but wouldn't denature the enzymes by raising the temp at the end of the mash, and running off into a kettle on the burner with the fire on. The mash temp finished right, but the runnings dropped in temp into the kettle and dropped further while I accumulated the runnings before firing up. All of that time conversion was continuing at lower temps that allowed the beta amylase to do its work, diminishing my unfermentables and yielding a more attenuative wort. Not sure if this may be your issue, but hope it helps. Review mashout procedure and turn on your gas or heat to your kettle once you've gathered an inch or so of runnings.

Interesting stuff. Idk I batch sparge by draining the tun, then adding about 185 degree water to do what I call a pseudo-mashout. The first runnings are not being heated immediately however. Perhaps I should give that a shot.

Tomorrow, I'm going to break out the hydrometer and see where I'm at.

 

[Pilgarlic]

Once the enzymes have been denatured at over 168 they won't reactivate if they cool down so you should be good. You might want to consider adding the 185 water at the end of your mash, before your first runnings, though. Add, stir and let settle, then take your first runnings.

 

[ludomonster]

I don't consider overattenuation to be a problem. It may be a symptom of some other problem if the beer doesn't turn out the way you want it with respect to body and taste.

 

[Pilgarlic]

What would "overattenuation" mean, other than attenuating more than intended? If you're not getting the beer that you intended to brew that's a problem, unless you don't really care what comes out of the fermentor.