The chart Chris had that I’m trying to get a hold of. Temp, pressure, and yeast strain all played parts in the tests White Labs did. That’s why I wasn’t too surprised at your results at that pressure.
Did some more reading, don’t know how I missed this before.
Briggs, Boulton et al. (p. 482) refer to trials under “moderate” top pressure leading to suppressed yeast growth as well as yeast damage, higher than normal pH, reduced head retention and other effects suggestive of autolysis and effects of increased dissolved CO2. It should be noted that what they call “moderate” pressurization is 1.2-2 Bar, and the trial conditions also included increased temperature. Nonetheless, they make an important distinction:
Brulosoohy (always taken with a grain of salt) suggested that 5-6 psig top pressure is merely equivalent to the hydrostatic pressure yeast experience in commercial fermentation. I wondered about this, whether it was apples and oranges. Briggs, et al. clearly state that the effects of hydrostatic pressure are quite distinct from those of top pressure, primarily, I gather, because a sealed (top pressurized) vessel does not allow the escape of deleterious substances.
Since I may ( I know I tried to dismiss it yesterday) have experienced three of the key effects mentioned in Briggs – suppressed yeast growth indicated by or the slow start and low attenuation, a higher than normal pH, and possibly reduced foam capacity (can’t confirm this yet, but samples may have suggested it) – I’m now having serious second thoughts about continuing with this procedure even at 5-6 psig.
Thoughts welcome.
Chris was pretty specific about 1 bar being the required pressure. I was thinking about trtying this, but after doing some more research it looks like it’s too finicky and has variable results. Can’t really see an advantage to it.
That’s where I am. I may come back to try it again, but until at least after I’ve tapped this first batch and really seen the results, I don’t feel like blindly risking any more batches. The big advantage for me was a built in supply of CO2 for sampling, but that’s not worth potentially damaging yeast and beer. I wonder if the effects are not only strain specific, but scale in unexpected ways. Maybe for some reason, 6 psig does to 6 gallons what 2 Bar does to 100 bbl.
Hey Denny, at least I’m rediscovering my experimental impulses! 
Then it’s not a total loss! Where did you come up with 6 psi, though?
I think you should wait until the keg is tapped and a beer is evaluated before making conclusions.
Or risking another batch. But now I’ve had more time to evaluate my data, and have a better idea of what the reported potential effects of pressure are, my data looks less like insignificant and more like science: an experiment which has repeated and confirmed someone else’s results.
6 psi seemed sufficient for dispensing samples, low enough to not carbonate, and, the decider, about as low as I can set my PRV without the stem being so near the end of the threads it gets pretty wobbly.
EDIT And of course it’s not a total loss, not just for getting me out of a rut. Underattenuated, I’ll have malt forward, low alcohol beer. I’d pay money for that.
Looking back at Kunze on the high temperature, high pressure, lager method, I see that the temperature is allowed to rise freely from the start, but atmospheric pressure is maintained until 50% AA, at which point the desired counterpressure is applied. Counterpressure is then reduced for lagering. This might avoid the detrimental effects of pressure fermentation as outlined in Briggs, but would make pressurization a pointless complication for my purposes.
When I added components to my all gravity outdoor system to bring it indoors there were a couple hiccups. I wouldn’t go back for anything now. That’s the way I look at this change you’ve introduced. One or two brews and I believe you’ll better understand the impacts.
You might try the White Labs yeast.
It would be nice to read the document Denny has been trying to get.
^^^^
Probably wise counsel. So let’s say I do pressure ferment the coming weekend’s brew. I will increase my pitch rate and oxygenation, and use a more attenuative yeast. This may help overcome any suppressed growth or underattenuation, and if it does under attenuate for the strain, at least the beer should still be adequately attenuated. These may be the kind of adjustments needed. Specifically that means: I have some Notty, very attenuative. I’ll build up a decent starter of that (yes a starter from dry yeast) and oxygenate well at pitching. Then maybe try repitching next time. Can compare this batch, normal Notty performance, and a repitch. Should be useful data.
Another adjustment occurs to me: if it’s pressure during the growth phase that’s harmful, I might pressurize the fermenter at pitching just to set the adjustable PRV, then release all the pressure through corny lid PRV. Then pressure won’t build nearly as early in the yeast’s life cycle.
If all these adjustments are needed and work, then the reps from the yeast manufacturers seemingly gave an oversimplified and optimistic opinion of how their yeasts would perform. They will receive a full report.
I forget, was there a hypothetical benefit to the pressure fermentation? What was it?
There are various claims about reduced esters and fusels, but Brulosophy found no significant difference in flavor. Others think it therefore allows rapid fermentation at very high temperatures, but that could be a misunderstanding of the process Kunze describes. More experiments are probably needed.
For me, the only benefit I’m after is just a simple, elegant way to have a completely closed system, the PRV replacing an airlock with its potential for gas exchange and suckback, and with added ease of drawing samples (no need to drag a CO2 supply to the ferm chamber every time I sample,) provided I in fact DON’T otherwise affect fermentation.
Those who are already spunding could integrate this into a one-vessel system.
Good discussion. I still plan to use a blow-off on my kegmenter until the Tilt shows me some progress on the fermentation and I push the beer to a keg.
I really wanted these new kegmenters to:
- reduce the use of large, dangerous glass vessels (I will still use them, just less frequently)
- eliminate the need to open the fermenter to transfer
- provide samples without jeopardizing the batch with oxygen
And if I find a way to eliminate the airlock/blow off without compromising fermentation, we can both tidy up our rigs. :) (Got some Notty on the stir plate, will proceed with the adjustments mentioned above this weekend.)
BTW tidying up in the basement I just ran across a pile of stoppers, s-airlocks and a couple of carboy draining thingies. And remembered how happy I am that I no longer have any carboys, however my current fermenter is configured!
There will definitely be some equipment that is used less frequently. Not sure yet how these new fermenters would respond to a fruit beer, for example. I don’t brew them often, usually once per year, but when I do I use real fruit!
Yeah, peaches are definitely bigger than poppets! ;D
If you are looking to perform a more closed fermentation system, why not use a Unitank?
A simple corny keg can be used for this. Afix a blow-off tube setup (you will definitely need one, even with a lower volume - 4.5 gallons in a 5 gallon keg) to the gas-in post. When you reach a specific gravity approximately 4 points above your FG (as determined by recipe repeats/fast ferment test), the all you have to do is remove the blow-off setup and seal up the lid of the keg with about 10 psi to seat it. Let the beer naturally carbonate in the keg.
If you close up too early, you can always use a spunding valve to monitor carbonation progress.
And a floating pickup can go a long way to improve clarity at a faster rate.
But that’s not what I’m after. My fermenter is a 10 gallon corny, so no need for blow off. I don’t want to carbonate in the fermenter because I… well all of this was the premise for this thread. If you read from the top you’ll see what the goals are.
More reading, more concerns. Yeast fermented under pressure will literally explode when decompressed at the end of fermentation, making harvesting for repitching problematic in this system. (This was not addressed by Brulosohy, as it doesn’t seem to be part of any of their processes.) For me this is a dealbreaker. In the high pressure lager process described by Kunze, yeast can be pulled from the cone before counterpressure is applied after 50% AA, or the fermenter can be very slowly (over a week or more) decompressed after racking. I can only harvest from my 10 gallon corny after fermentation is complete, and slow decompression is one more complication that would counter any convenience the system might afford; and if it would disrupt my timetable, I can’t imagine commercial brewers are pleased with the loss of use of tank space. (And going to a conical is not in my future, the very consideration is part of the past. I’ve probably discussed elsewhere how I chose the corny over any such vessel. Suffice it to say I find it pretty much ideal.)
Brulosophy seemed baffled that they couldn’t find any breweries fermenting under head pressure. It’s becoming clearer to me – aside from the point that Brulosophy didn’t understand the difference between hydrostatic and head pressure.
I will continue research and see if some feasible hybrid process emerges. But Denny may have nailed it: too finicky, no obvious advantage. Guess for now I’m lugging CO2 tanks and lines around.