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Mike,
Our typical DO targets range from 8-14ppm. With weisse, we generally shoot for a slightly higher DO (14-18ppm). For the last 3 brews the DO numbers were 19.19ppm (Gen 1), 14.55ppm (Gen 2), and 16.02ppm (Gen 3). These are pulled and measured directly from the fermenter after KO. So, our DOs were within our normal range. I did not find any leaks in the aeration system. The first batch is a starter, but from there on we crop the yeast.
Dana,
We tend to have very aggressive fermentations with this yeast strain so my initial thought was we were losing a bulk of the active healthy yeast through krausening out the blow off arm. With the last brew, we added Fermcap ECO (vegetable oil-based antifoam) to the fermenter. That brew did not krausen out at all but still finished in the same range as the first two. Thanks for the articles. I will read through them.
To answer your questions Brendan,
- Pitch rate, cell counts, and harvesting technique were done all according to our SOP. Nothing out of the ordinary except a higher cell count for the 3rd batch. The first 2 were on target. The cell counts were also coming in at 98% and above for viability. No other changes in KO temp or KO duration. With this brand, we knockout at 15.5°C and free rise to 20°C and hold at that temperature until terminal is reached.
- From gen 1→2 we tend to be able to crop less yeast but from gen 2 and up we usually see a significant amount of more yeast floc out and settle at the bottom. We did not notice anything different this time around. Our wort aeration was within our target 14-18ppm. The DO reading is done with a Hach HQ40d.
- I looked at the brewsheets and we hit the target pitch rates for each batch. I think slurry density was fine. The brewers will usually inform me if the yeast was very thin or the pitch runs to beer before targets are hit. No extra experiments were done with the yeast.
- I did not check for starch conversion in these batches and that's definitely something I plan on doing next time we brew this brand (likely won't be for a couple months though). No change in base malt lots and looking at the COA, FAN was well within the specified range. For the first 2 batches we added Yeastex 82, so FAN shouldn't have been an issue. The 3rd batch I removed the Yeastex and just added Zinc to the wort. However, there was no significant difference in fermentation. We normally take a cell count after KO has finished but next time I will take a cell count of the yeast slurry before pitching to confirm counts.
After further thought and research, I tend to agree that the yeast may just be overly stressed out and we might need to alter our propagation/growth steps with this yeast for future brews. I have also talked with my yeast supplier and he thought it could be an issue with too quick of a step up to our normal size batches (20-40 bbls) and that may be affecting the yeast's ability to metabolize sugar later in fermentation.
Thanks for all your input.
Original Message:
Sent: 06-14-2024 14:53
From: Brendan McGinn
Subject: Premature Yeast Flocculation
The increases in pH point me towards this being a result of a not as healthy of a ferment as you are used to seeing. A few questions for you:
1 - Have there been any other changes in pitch rate, or cell counting and harvesting technique or personnel? It seems like the fermentation is starved somehow. I have found that some yeasts can produce beers with a lower initial drop in pH due to excess O2 and/or increases in pitch rate. Perhaps the O2 flow is stifled in some manner causing your increase in pH. Have you had any changes in brewing hoses or the length of hoses used from the kettle to the fermenter? Are knock out temperatures and durations the same as usual?
2. Do you find more or less yeast in the bottom of the fermenter (or however you crop your yeast) after this issue occurs? The times I have been surprised that there's significantly less yeast in the bottom of a tank than expected has usually been after a slow/stalled fermentation that was traced back to improper wort aeration (dial set to wrong setting or O2 cylinder running out during KO, etc).
3. Do you or any other brewers perform any less documented "extra" experiments on the side that would cause a more drastic underpitching in this particular batch or situation? A well meaning brewer could try to pitch less to drive flavor but unknowingly already be short on yeast or O2. It seems like this isn't the case, but sometimes solving something like this takes a big step back.
4. Have you checked for starch in your beer and wort with iodine tincture? Are your temp probes calibrated and in good working order? A change in lots of your malt bill could leave you with insufficient enzymes to get a full conversion. - Bench top tests fermenting fine suggest that the conversion is complete. Since you've had successful forced/benchtop ferments, I would look for something with the O2 or possibly upping your FAN, and likely both. Have you tried adding any Zinc to your wort? Are you able to perform a cell count and check for viability at the time of pitching?
Since this sounds like it started with a new culture, my gut says your yeast is stressed and deficient in nutrients from the first fermentation. Definitely curious if you get to the bottom of this! Good luck!
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Brendan McGinn
Director Of Brewing Operations
Zipline Brewing Co
Lincoln NE
(402) 937-1994
Original Message:
Sent: 06-13-2024 13:05
From: Michael Billon
Subject: Premature Yeast Flocculation
Yeast typically used with hefeweizen style beers have inherently low flocculation potential, so I'd be skeptical that you're experiencing true PYF. Instead I would think this is just a stuck fermentation, and my immediate thought after reading about your issue is that you are not providing enough DO with your initial knock out (especially if this is a starter and not cropped yeast). That's why on the bench top, the issue goes away.
So if I were troubleshooting this, I would grab some soapy water and look for leaks in your aeration setup, and if that doesn't turn up anything, consider increasing DO at knockout. If that still doesn't resolve the issue, that's when I might turn my attention from the yeast and start looking at other aspects of the brew
Hope that helps,
Mike
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Michael Billon
QC Specialist
Allagash Brewing Co
Portland ME
(207) 878-5385
Original Message:
Sent: 06-11-2024 15:30
From: Anonymous Member
Subject: Premature Yeast Flocculation
This message was posted by a user wishing to remain anonymous
Hi All,
We are having issues with premature yeast flocculation (PYF) in our last few batches of our Hefeweizen which is causing problems with attenuation. We are not seeing issues with any other brands so it seems to be yeast strain specific.There hasn't been any change in water, mash, or fermentation profile. Starting cell counts have been good and viable. Fermentation starts normally and progresses fine until it reaches about 5°P. At that point fermentation begins to slow down until hit hits terminal between 3.5-3.8°P. This brand normally finishes around 2°P. I also ran a forced bench top fermentation that attenuated normally. So, it seems with constant agitation, this yeast is able to finish the job. The only thing that I have seen issues with is pH. We usually see a drop of pH to around 4.0 with this brand but lately it hasn't been dropping below 4.3. I am also seeing a higher increase in pH towards the end of fermentation (4.5-4.6 range). In terms of sensory, we haven't noticed any significant differences between this current batch and what we have on tap at the pub. Flavor profile is very similar and I am not tasting any 'rubbery' off-flavors which would indicate autolysis. I have read that PYF can be malt-induced but we haven't had any issues with any other brands that would point towards base malt being the problem. Maybe low yeast vitality? Any info is appreciated. Thanks.