Over attenuation?

[Moody_Copperpot]

Just learned of this after a few years of brewing, and about a year and a half at AG. What can cause this?
I did two batches of a holiday ale, both with the same yeast (s-04). The first had an OG of 1.070 and this was at 87% efficiency. The FG was 1.010. Its about two weeks since ive bottled it, and its got a really strong alcohol bite that im unhappy with, and im hoping will settle out a bit.
The second batch was not as high in efficiency, had a lower floccuation, and tastes great. It's on tap now, and I love it.
So does it sound like over attenuation on batch 1?

 

[NordeastBrewer77]

sounds like great attenuation! the booze bite should mellow in time.
with efficiency and attenuation like that, i'm guessing you mashed quite low?

 

[Moody_Copperpot]

sounds like great attenuation! the booze bite should mellow in time.
with efficiency and attenuation like that, i'm guessing you mashed quite low?

I did, I mashed at about 152.

 

[Moody_Copperpot]

Does the efficiency somehow play a role here too?

 

[NordeastBrewer77]

well, lower mash temps can lead to more fermentables, so yeah. i purposely mash low for beers that i want to finish dry. for an IPA for example, i mash at 149 for 90 mins. for beers i want some residual sweetness in, i mash higher. for something like a red, i might mash at 155 to get more unfermentable sugar in the wort.

 

[Moody_Copperpot]

Right, but how can I avoid over attenuation from lower mash temps?

 

[NordeastBrewer77]

mashing low will create a more fermentable wort. maybe try a lower attenuating yeast, mash a bit higher, adding an unfermentable sugar to the wort.

 

[Moody_Copperpot]

So it's really just a risk with certain strains then if you mash low?

 

[WildGingerBrewing]

At what temp did you ferment? In my experience, hot alcohol comes from fermenting too hot.

 

[NordeastBrewer77]

So it's really just a risk with certain strains then if you mash low?

well, if you have a strain that gets 77% attenuation fermenting a wort that is 80% fermentable, it'll chew through 3/4 of those fermentables. if you have a strain that gets 67% atten. in the same wort, only 2/3s of those sugars are fermented.
conversely, that yeast with 77% atten. in a wort with 75% fermentables, less sugars will be fermented.
it's a balance of mash temps and the % attenuation of the yeast. if you want dry beer, mash low and use a high attenuator like s-05. for a beer with some residual sweetness, mash higher and use a lower attenuating strain like wy1098. low mash temps with a low attenuator or high mash temps with a high attenuator will get you somewhere in between. there's many factors that come into play here. as another poster said, fermentation temps play a role in how much the yeast attenuates as well.

 

[Moody_Copperpot]

I have perfect conditions in my basement. It's a finished basement and stays at a constant 62-65 year round, so the hot temp isn't the culprit. Currently it's a steady 62 where the beer is sitting.

 

[Moody_Copperpot]

well, if you have a strain that gets 77% attenuation fermenting a wort that is 80% fermentable, it'll chew through 3/4 of those fermentables. if you have a strain that gets 67% atten. in the same wort, only 2/3s of those sugars are fermented.
conversely, that yeast with 77% atten. in a wort with 75% fermentables, less sugars will be fermented.
it's a balance of mash temps and the % attenuation of the yeast. if you want dry beer, mash low and use a high attenuator like s-05. for a beer with some residual sweetness, mash higher and use a lower attenuating strain like wy1098. low mash temps with a low attenuator or high mash temps with a high attenuator will get you somewhere in between. there's many factors that come into play here. as another poster said, fermentation temps play a role in how much the yeast attenuates as well.

Thanks for that info. Very helpful! I generally use 05 anyway, but wanted a different strain for the holiday batch. So really high efficiency can lead to over attenuation, or at least play a part in it, depending on mash temps and yeast used. I generally get 82-86%, so if I'm using a particular yeast I can increase my mash temp.

 

[NordeastBrewer77]

you still want good efficiency, like it seems like you're getting. the key would be to bump the mash temps up a bit to make sure some of those sugars are unfermentable.
as far as yeast, s-05 is a beast, i get 77-80 percent attenuation from that strain. really nice for american ales like IPA. if you're looking for something a bit less attentive, try an english strain, i like 1098 a lot, or the 1332 northwest ale is a cleaner american strain that'll leave some residual sweetness in your beer.

 

[Moody_Copperpot]

Right, that's what my muddled post was trying to get across, haha; that I can raise my mash temp to lessen the risk of over attenuation.
As for the yeast, I am about to take my first stab at liquid yeast with a brewer buddy of mine. 05 has been so good to me, that I haven't strayed.

 

[HopDr]

I think there is some confusion about terminology here. You are not really over attenuating, yeast does what it does. When people talk about apparent attenuation of a strain of yeast, it is really an estimate of how much of the fermentables it will usually ferment under good condition. Your results may vary. This has nothing to do with you efficiency.

If you are getting more attenuation than you expect (i.e. difference between OG and FG is more than you expected) it is (likely) that you just have more fermentables than you expected (or less unfermentables, I guess- the proportion is off). This is where your mash comes in. It still is not really a function of efficiency of your mash though, it is a function of your mash schedule and your ingredients. It is possible to have very high efficiency with less fermentables, like what you would want for a heavy bodied beer, or low efficiency with a higher proportion of fermentables. They are separate issues.

 

[NordeastBrewer77]

Right, that's what my muddled post was trying to get across, haha; that I can raise my mash temp to lessen the risk of over attenuation.
As for the yeast, I am about to take my first stab at liquid yeast with a brewer buddy of mine. 05 has been so good to me, that I haven't strayed.

sounds like ya got it!
i've used mostly wyeast from the beginning, but started using 05 because i wanted higher attenuation in beers like my CDA and maltier IPAs, and quickly learned why so many people like it. it's reliable, easy, and probably going to replace the 1056 that i used to use. liquids are great though, i use 1272 american II in a lot of my pale ales, and the liquid english strains are the way to go with british styles, IMO. you just have to make sure to pitch large, healthy starters with those english yeasts.
good luck man, and happy brewing!

 

[Moody_Copperpot]

Tons of good info here! Thanks so much, everyone!