We've run into a strange issue with our BSI1 (Chico) ale yeast when fermenting any of our Maris Otter base brews, particularly our IPA. Yeast seems to reproduce well according to cell counts and ferments strong until around 70% attenuation and then fermentation ceases, or slowly drops for anywhere from 4-6 additional days and yeast health at harvest is terrible. We've typically seen 80+% attenuation in the past and we still see that activity on non-Maris Otter brews (and non-BSI1 brews). I'd like to get this yeast to attenuate back to 2.5-3 plato rather than the 4.5-5 plato it's finishing at for our IPA. I've been brewing on this system for 2.5 years and this is a new issue within the past 6 months. The troubling part is that we're not seeing similar behavior across all brews so it's been difficult to pinpoint the cause. We typically brew 15-17 bbl batches.
Facts:
1. IPA OG is roughly 15.0. This is our highest OG regular brew.
2. DO at knockout is 11-13 ppm. Constant for all brews.
3. Fermentation temp is 68, knockout temp is slightly lower. Constant for all BSI1 brews.
4. Pitching at a million c/ml/p at 90+% viability. Constant for all BSI1 brews.
5. Yeast nutrients provided in boil at 15 minute mark.
6. Malt analysis for Maris Otter shows no drastic variance between batches.
7. Typical mash temp is 156, mash and wort pH within acceptable range.
8. Strike water total alkalinity typically 100-120 ppm.
9. Sparge water <170 degrees.
We thought aeration was for sure the cause but have confirmed our O2 flow at knockout and swapped out our O2 stone as well. We're now focusing on hot-side and wort quality. Given the facts above, can you think of any hot-side causes of this yeast performance? I combed through all the yeast threads and couldn't find solutions that seemed applicable to our situation. Any feedback would be appreciated. Cheers.
Facts:
1. IPA OG is roughly 15.0. This is our highest OG regular brew.
2. DO at knockout is 11-13 ppm. Constant for all brews.
3. Fermentation temp is 68, knockout temp is slightly lower. Constant for all BSI1 brews.
4. Pitching at a million c/ml/p at 90+% viability. Constant for all BSI1 brews.
5. Yeast nutrients provided in boil at 15 minute mark.
6. Malt analysis for Maris Otter shows no drastic variance between batches.
7. Typical mash temp is 156, mash and wort pH within acceptable range.
8. Strike water total alkalinity typically 100-120 ppm.
9. Sparge water <170 degrees.
We thought aeration was for sure the cause but have confirmed our O2 flow at knockout and swapped out our O2 stone as well. We're now focusing on hot-side and wort quality. Given the facts above, can you think of any hot-side causes of this yeast performance? I combed through all the yeast threads and couldn't find solutions that seemed applicable to our situation. Any feedback would be appreciated. Cheers.
Comment