« on: May 17, 2013, 06:56:32 AM »
Confused ... :confused:
I brewed a Rogue Double Dead Guy clone, mashed at 152F - it started at 1.084 and finished at 1.010, fermented with Wyeast Pacman. No mash out.
Beersmith calculates that as a 82.7% attenuation. OG measured with a refractometer and FG measured with two hydrometers.
Wyeast's stats are 72-78% attenuation for this strain.
The yeast was about 11 months old, smelled and tasted good, and pretty creamy white. I made a 2L starter with the decanted slurry and it took off in about 4 to 6 hours.
I hit the wort with O2 and pitched the decanted starter. Within 4 to 8 hours it began to show signs of fermentation.
The beer fermented @ 65F in a refrigerator (measured by a thermowell) for about 3 weeks. I let it sit on the yeast cake @ 45F for another three weeks. Approximately 6 weeks total.
This recipe should have finished around 1.018 - 1.020, mine however continued to 1.010. As a result, it is much drier with an alcohol bite. At 6 weeks old, it's not so green anymore.
With that being said, what in your opinion might account for the higher attenuation?
If anything, I suspect old/aged yeast would be less attenuating, unless it mutated.
What about sitting on the yeast cake for an extended period? After three weeks @ 65F, the yeast should have been entirely done, and at 45F, the yeast should be dormant and inactive.
Would over pitching push it lower?
Would no mash out increase attenuation?