High attenuation: always a contamination?

[messersc]

Hi,

I'm bottling a beer using Fermentis Safale US-05 right now that attenuated to 83.5%. The beer tastes as it should right now (it's a pumpkin ale that's very lightly spiced, not nearly so much so that spices would mask clearly foul flavors). I know that I have to wait and see, but since I'm impatient: can I assume this is infected, or do I have a chance at a clean beer?

Thanks.

 

[GuldTuborg]

Is the AA the only reason you think this is infected? It's very easy to get 80%+ AA with most yeasts, with no infection. Hell, some saison yeasts will get you to around or over 100% AA by themselves. Relax, and all that.

 

[bierandbikes]

The US-05 will easily go over 80%. I brewed an Imperial IPA that went to 88.8% (FG 1.009) and was outstanding. The one thing that I have noticed (maybe with the bigger IPA only) is that you need to give it some extra time in the bottles. However, you have nothing to fear at 83% AA. It may go lower.

 

[william_shakes_beer]

Attenuation is related as much to fermentability as it is to yeast strain and temperature. Mash low, simple sugars, highly fermentable wort. Mash high, more complex sugars, less fermentable wort. (But, IMHO, tastier)

 

[BigFloyd]

Attenuation is related as much to fermentability as it is to yeast strain and temperature. Mash low, simple sugars, highly fermentable wort. Mash high, more complex sugars, less fermentable wort. (But, IMHO, tastier)

Yep. It's not all that unusual for a yeast to attenuate beyond (or less than)the range given by the mfg.

 

[messersc]

Thanks for the feedback. This is the fourth time I've used the same colony of yeast, and looking back at my results the attenuation has risen a little each time. Maybe I'm not top-cropping at quite the right time.

Anyway, I'm guessing from what you guys are saying that things are fine.

 

[messersc]

Is the AA the only reason you think this is infected? It's very easy to get 80%+ AA with most yeasts, with no infection. Hell, some saison yeasts will get you to around or over 100% AA by themselves. Relax, and all that.

Thanks for the help, all; it turned out to be the right advice. The beer is great. Doesn't come across as overly-dry, either. Carbonation was fine, too.