Pressurized Fermentation- Target Yeast Temperatures?

[micraftbeer]

I'm starting to explore fermentation under pressure. I keep reading that you can "ferment lagers at ale temperatures" because fermenting under pressure suppresses ester formation. Would this imply I no longer need to worry about fermentation temperature per se, and my year-round Michigan basement temperature of 63-65F will be suitable and I no longer need to worry about Igloo coolers with frozen 2L bottles of ice hooked up to a fermentation cooling coil?

These are some things I'll probably experiment with, so I'd be interested in hearing people's thoughts/understanding on the science involved here, plus any empirical/anecdotal feedback from personal experiments and taste testing.

 

[PaleRider76]

I haven’t tried a lager under pressure yet but have heard the same, as well as the beer finishing sooner than not under pressure. I have a pack of Imperial Urkel to use for this purpose when I get some time to do a lager. I have done ales under pressure though. Anecdotal: the things I like about fermenting under pressure is it keeps the krausen down and you then have the equipment needed to do pressure transfers to a keg. The same beers I made not under pressure in a bucket with an air lock sometimes have krausen all the way up to and including the lid - queue the blow off tube. In my fermzilla with a spunding valve it only goes up an inch from the liquid line at most even at very high temperatures with kveik.

 

[Rippchen]

I just did a split batch a few weeks ago. Two lagers one under pressure and one temp controlled. The pressure fermented lager was fermented at 67°F and 1bar (~1.2 psi). The non pressure lager at 50 °f with a diacityl rest before finishing the fermentation. The pressure fermented lager needed 3 days longer to ferment, but was perfectly drinkable since the first day after forced carbonisation the normal lager is still not. So it can take longer, but it works well ... at least for me.

 

[micraftbeer]

I've just completed two split batch fermentations, with blind taste testing planned at a backyard party in about 2 weeks. Both are recipes I've brewed before. First is a lager, one at 65f room temperature under pressure, other fermented at 55f (stupidly started at 55f instead of the 50f to replicate my previous great experience with this recipe- doh!).

Second one is a black IPA. Both of these fermented at same 68f temperature, but the pressurized batch I attached spunding at about the halfway point of gravity drop, and did the CO2 purged dry hop charge up through the collection ball at the bottom at the end of fermentation.

This is wrapped up in some equipment reviews I'm doing, and a resource post for Homebrewfinds. I'll share results as I get them.

 

[couchsending]

Some yeasts can handle pressure, others can’t at all.

Some lager yeasts seem to be unfazed, specifically 34/70 variants.

Some English strains can take a bit of pressure but it’s really only beneficial for the first few days of fermentation with ale yeasts. After those first few days removing the pressure and raising them temp is beneficial.

I’d be willing to bet most large commercial lager fermentation Is done under pressure at elevated temps.

 

[Snark_Wolf_Brewing]

Some yeasts can handle pressure, others can’t at all.

Some lager yeasts seem to be unfazed, specifically 34/70 variants.

Some English strains can take a bit of pressure but it’s really only beneficial for the first few days of fermentation with ale yeasts. After those first few days removing the pressure and raising them temp is beneficial.

I’d be willing to bet most large commercial lager fermentation Is done under pressure at elevated temps.

Don't remember exactly where I read it, but I recall an article online that said most of the major commercial breweries here in the US switched to pressure fermentation sometime in the 1960s in order to turn out product at a faster rate to maximize profits from sales.

 

[micraftbeer]

First tasting of my "Munich lager" from my split batch. Color slightly darker on my cold fermented lager than the pressure one. I haven't done the blind triangle test yet, but there are notable aroma differences (slight, but notable), and taste is slightly different (a bit more undesirable from the cold ferment one). My initial impression was the carbonation mouthfeel was slightly "smoother" on the pressure ferment one, but I really need blind taste test to confirm that one- it was very slight. More specific/useful tasting notes later once I can do this blind without knowing which is which.

 

[micraftbeer]

Blind taste testing (I guess technically "semi blind" since I knew the variable that was different) found I was unable to tell the difference between these two lagers. That being said, both were very harsh/astringent, not at all like my last brew of this recipe. At this point, I'm either thinking I had a defect in the mash or the batch of yeast, or it simply needs to lager more to clean up the harshness. The wort was from an 11-gallon batch split in two, so if anything went awry there it would affect both, and the yeast was built up from a big starter, decanted, and then split evenly between batches.

 

[odie]

going to be doing a Czech pils today. S-23 yeast since I'm outta 34/70 I'm fermenting in the serving keg. Was gonna ferm under pressure at ale temps. What pressure is too much? or Too little? I have some 30 psi PRV valves I was gonna try. Is that too high for the yeast production?

 

[Snark_Wolf_Brewing]

going to be doing a Czech pils today. S-23 yeast since I'm outta 34/70 I'm fermenting in the serving keg. Was gonna ferm under pressure at ale temps. What pressure is too much? or Too little? I have some 30 psi PRV valves I was gonna try. Is that too high for the yeast production?

From what I've seen so far on the topic of pressure fermentation, anything between 5 to 15 psi is perfect, although I have seen a few brewers on YouTube who report going all the way to 30 psi with no issues. Generally speaking, the current consensus says anything over 15, and you run the risk of off flavors and slowing down the yeast's ability to reproduce and ferment the available sugars to alcohol.

 

[odie]

I have a 10 PSI PRV that I can use for the first couple days and then swap it to the 30 for finishing and carbing up.

Would I just skip the blow-off tube and leave the keg sealed and the PRV controls everything?

 

[Snark_Wolf_Brewing]

I have a 10 PSI PRV that I can use for the first couple days and then swap it to the 30 for finishing and carbing up.

Would I just skip the blow-off tube and leave the keg sealed and the PRV controls everything?

I've heard of brewers skipping the blow-off tube and using a spunding valve right from the start. They suggest using something like Fermcap S to keep the krausen down if you're fermenting in a corny keg.

 

[odie]

my first few ferment in the keg batches only had CO2 blow off...no krausen in the blow tube or water bucket...and those kegs were a full 5 gal of wort, little head space. but could just be the yeast and temps were not producing much krausen.

 

[Snark_Wolf_Brewing]

my first few ferment in the keg batches only had CO2 blow off...no krausen in the blow tube or water bucket...and those kegs were a full 5 gal of wort, little head space. but could just be the yeast and temps were not producing much krausen.

Could be.

 

[Snark_Wolf_Brewing]

Haven't seen much on s-23 yeast being used for pressure fementation, so I can't say for 100% certain which approach would work best, spunding straight from the start or using a blow-off tube for the first few days before switching to a PRV or spunding valve.

 

[odie]

Might just skip the blow off. If it spews out the PRV I can just hose off the keg until it settles down. Basically the PRV is my spund valve. I bought some low PSI valves to replace the high pressure original.

 

[Snark_Wolf_Brewing]

Might just skip the blow off. If it spews out the PRV I can just hose off the keg until it settles down. Basically the PRV is my spund valve. I bought some low PSI valves to replace the high pressure original.

The Czech Pils sounds awesome. Good luck, and let us know how it turns out.

 

[micraftbeer]

Here's the info I've been gathering from different sources (Blichmann, Wyeast, White Labs). In no particular order:

1. Blichmann/White Labs did a fermentation trial with a lager cold fermented under 0 psi, warm fermented (I forget exactly, but around 70F) at 0 psi, warm fermented at 15 psi/1 bar, and warm fermented at 30 psi/2 bar. The conclusion from tasting was 15 psi warm & 0 psi cold ferment were most preferred. 30 psi warm started to show some issues. And well, you can guess how the 0 psi warm fared...

2. Fermenting warm will produce more esters due to the more rapid yeast metabolism. Pressure slows/changes metabolism and hence stiffles the esters. It's not a direct 1-for-1 trade-off you're doing, but you can think of it that way. So if you ferment warm, but don't have much pressure, you might still get too much ester character. So the amount of pressure you want to ferment under is going to be related to how "warm" you ferment.

3. Recommendations for ale yeast is ferment at normal temp, 0 psi, until about 1/2 way through fermentation, then spunding to jumpstart carbonation. Recommendations for lager yeast are to start at 0 psi, but with spunding set to your target (15 psi) pressure. I presume this is so you're not stressing the yeast out during their initial growth phase, but that's just me trying to make an educated guess.

4. Not related to temperature or pressure, but it's not recommended to use your PRV as your spunding. The PRV is supposed to be your mechanical fail-safe to prevent a dangerous uncontrolled build-up of pressure in your keg. If you try to regulate with a PRV, it will be at risk of sticking/clogging and then you have no backup. You could probably rationalize your way to why it's OK, but it's not considered a safe practice. It's maybe akin to controlling the speed of your car by short-circuiting the fuel cut-off inertia switch, while you keep your pedal mashed to the floor. Sure, it might work, but...

 

[North_of_60]

3. Recommendations for ale yeast is ferment at normal temp, 0 psi, until about 1/2 way through fermentation, then spunding to jumpstart carbonation. Recommendations for lager yeast are to start at 0 psi, but with spunding set to your target (15 psi) pressure. I presume this is so you're not stressing the yeast out during their initial growth phase, but that's just me trying to make an educated guess.

Interesting, I’ve done two ales in a full corny keg at 70 degrees, starting at 0 psi with the spunding valve set to 15 psi. One had a slight amount of blow off right at the beginning that stopped as soon as the pressure built up. both were good beers. I use a floating dip tube so I served in the same keg that I fermented in.

I’m going to brew a lager next week. I had thought of pre-charging to 15 psi. My thinking is that we are using pressure rather than temperature to control the fermentation process, so why not start with the desired pressure? With temperature controlled fermentation We pitch our yeast at or near our desired temperature.

 

[micraftbeer]

Yeah, my brain struggles between competing thoughts of: A) 0 psi to start because you don't want to stress out the yeast during their initial multiplication/growth phase, B) Everything I've read says the most important part of the fermentation process to have the right temperature is at the start. So a 70F ferment starting at 0 psi seems like it would already "do its damage" for flavors/esters.

Both of these seem to have some validity in my mind.

 

[North_of_60]

I know what you mean. I think at this point in time we are all experimenting.

 

[odie]

My salted caramel brown came out pretty close to what I expected.

Keg ferment, 68', blow off tube, switched to pressure ferment after a few days, no spunding valve, frequent release of PRV, raise to 30 psi, bleed to 5-10 psi, repeat until done, served in same keg, bottom dip tube, first pint was yeast harvest. Got 4 more beers done this way in cold storage right now.

Version 2.0 was started yesterday. Got a lager that went straight into the keg with some harvested yeast cake and sealed, temp at 70', capped off with a 30 psi PRV (pops at 35 and resets at 25 when I tested it), not pressurized so when the yeast starts up the psi will rise from zero to the PRV setting, floating dip tube this time, beer will be served from same keg and remain on the yeast cake until empty.

 

[duffy5018]

I just ran across this blog post yesterday. The research cited here indicates that for the first 24 hours, yeast don't need and will be better off with no pressure, then you can pressurize away. My next batch, I plan on pressurizing the corny to 15 to seal it, throwing a spunding valve set at 2 psi or there about so it's essentially not under pressure, then pressurizing to 15-20psi the following day.
http://scottjanish.com/fermenting-dry-hopping-pressure/

 

[odie]

well, filled the keg on Monday night with a Czech pils fresh from the kettle, all the trub strained out. pitched an old S-23 yeast cake Tuesday morning and closed the keg with a 30 PRV at 70 degrees and a pressure gauge. I did NOT burst seal the lid with CO2.

After a day got nothing on the gauge. So i guess any fermentation gas is bleeding past the big lid o-ring. So I shake the keg to agitate the CO2 in the wort and it bumps the gauge a few psi. I guess enough to seal the lid. Next day the gauge is at 30 psi. In retrospect, I probably should have left it alone and waiting to see if the yeast just needed a little more time to kick into high gear and produce CO2 at an increased rate. Sealing the lid is an function of the rate of CO2 production exceeding the rate of CO2 leaking past the lid in order to "seat" the o-ring to complete the seal.

Not getting any krausen blasting thru the PRV either. So I guess the pressure is keeping the krausen in check. No blow off tube was used. Maybe 2" of head space between the top of the wort and the PRV. I thought for sure krausen would be getting burped out the PRV. I bleed the PRV a bit every so often but probably don't need to.

Supposedly yeast can take a few thousand PSI. But stop reproducing around 37 PSI. So my 30psi PRV is probably ok.

Pressurized Fermentation Process and Benefits | Homebrew Academy.

 

[North_of_60]

You have probably seen this podcast: Pressure Fermentation with Chris White, John Blichmann- BeerSmith Podcast #163.

Brad Smith, Chris White and John Blichmann discuss an experiment that White and Blichmann did on pressurized fermentation. I don't remember for sure but I believe the yeast used was WLP925 HP. The pressure fermentations and 0 BAR were performed at 68 F (room temperature) while the lager was fermented at lager temperatures. White Labs did a laboratory analysis and found that the ester levels were lower on the pressure fermented beers than the lager. Blichmann also had a group of beer judges sample the beers. They were all able to identify the lager and found that flavor wise the sweet spot for the pressure beers was 1 BAR (14.5 psi).

The chart below shows some of the data. There is a link on the above web page to an Excel spreadsheet of White Labs report.

	Lager	0 BAR	1 BAR	2 BAR
Ethyl Acetate	33.01	40.5	23.52	19.7
Isoamyl Acetate	2.18	2.78	1.66	1.26
Diacetyl	32.07	10	12.61	12.2

They used a controlled temperature of 68 F room temperature. In my house room temperature ranges from 70 to 74 F in the summer and from 68 to 70 in the winter. I wonder how much difference that is going to make.

The encouraging news is that there is experimental data that pressurized fermentation does work to make lager like beers at higher temperatures.

 

[solsbrew]

You have probably seen this podcast: Pressure Fermentation with Chris White, John Blichmann- BeerSmith Podcast #163.

Brad Smith, Chris White and John Blichmann discuss an experiment that White and Blichmann did on pressurized fermentation. I don't remember for sure but I believe the yeast used was WLP925 HP. The pressure fermentations and 0 BAR were performed at 68 F (room temperature) while the lager was fermented at lager temperatures. White Labs did a laboratory analysis and found that the ester levels were lower on the pressure fermented beers than the lager. Blichmann also had a group of beer judges sample the beers. They were all able to identify the lager and found that flavor wise the sweet spot for the pressure beers was 1 BAR (14.5 psi).

The chart below shows some of the data. There is a link on the above web page to an Excel spreadsheet of White Labs report.

	Lager	0 BAR	1 BAR	2 BAR
Ethyl Acetate	33.01	40.5	23.52	19.7
Isoamyl Acetate	2.18	2.78	1.66	1.26
Diacetyl	32.07	10	12.61	12.2

They used a controlled temperature of 68 F room temperature. In my house room temperature ranges from 70 to 74 F in the summer and from 68 to 70 in the winter. I wonder how much difference that is going to make.

The encouraging news is that there is experimental data that pressurized fermentation does work to make lager like beers at higher temperatures.

At the end of that podcast they talk about doing ale experiments with pressure fermentation with temperatures in the 80s. I'm curious about those results too.

 

[renstyle]

NOTE: I dunno what qualifies as "resurrecting a dead thread", but this is pertinent to my post so figured why not add it here rather than re-hash it all again in a new post? If this is contrary to forum etiquette, please let me know.

I am currently pressure fermenting a BoPils, about 18L in a 23L corny keg. First time trying this myself. 40-ish hours in and the blowtie is whistling away.

Fermentation is running at 18-20C/64-68F @ 12 PSI with 1 sachet of 34/70.

Gravity has dropped from 1.040 to 1.022 heading to (hopefully) 1.007.

From what others have related in the posts above, this should be good to go. Will keep you posted.

 

[renstyle]

<removed pic of brew in cold crash>

wrong forum, this has 2001 yeast. the 34/70 is still in a fermenter. sorry for any confusion.

 

[DuncB]

@renstyle
That is looking good, my American amber is day 3 finished ferment mostly, risen to 27psi over the last 24 hours and the yeast is dropping like rain in the fermenter at 31.5 celsius to finish off ( might get another point or two down in next few days ) . Using opshaug kveik. Not sure on gravity but ispindel says 1.040 to 1.007 I suspect more like 1.012 but I'll find out once I dump the yeast tonight and get a sample to top up the collection bottle before reattaching it.
My plan is to move the fermenter to an outside room in another 48 hours to continue clearing, we're cooling down here with night temps of about 5 celsius.

 

[renstyle]

the pic I posted was of a different yeast, and landed in this overbuilding post.

I am doing a pair of BoPils side by side, wasn't a split wort batch, but same recipe, only difference is the yeast: WY2001 that I did an overbuild, and another with 34/70.

Still somewhat "green", but for a Pils 7 days out it's looking pretty good.

The 34/70 is heading in the same direction.

 

[renstyle]

Okay, here is the 34/70:

I did a <very> slow closed transfer from the ferm-keg to the serving keg with a spunding valve.

No other finings added other than 3C/38F and 23 days lagering.

Tastes lovely

 

[humpadilo]

I just got my pressure fermenter and I’m loving it. I’m far from an expert, hell, I haven’t taken a gravity reading in years. I figured I’d post what I’ve learned. I hear people saying not to ferment at a time high PSI. I’ve done a hand full of batches so far and almost all of them are lagers. I set my PSI to 25-30 and all of them have come out great. I tend to keg 12-14 days after brew day and start drinking the next day or so. They have all been great. Except one, but that was the grain bill I screwed up.

They do get way better the further I get into the keg though, so some aging would help. But I haven’t seen any of flavor because of the high PSI. I suspect it could be better at lower PSI, but right now I’m just getting a baseline of how fast I can turn out good beer. Maybe after I get a head in my brewing I’ll be able to lower the PSI and see how if the flavor changes.

 

[renstyle]

I just got my pressure fermenter and I’m loving it. I’m far from an expert, hell, I haven’t taken a gravity reading in years. I figured I’d post what I’ve learned. I hear people saying not to ferment at a time high PSI. I’ve done a hand full of batches so far and almost all of them are lagers. I set my PSI to 25-30 and all of them have come out great. I tend to keg 12-14 days after brew day and start drinking the next day or so. They have all been great. Except one, but that was the grain bill I screwed up.

They do get way better the further I get into the keg though, so some aging would help. But I haven’t seen any of flavor because of the high PSI. I suspect it could be better at lower PSI, but right now I’m just getting a baseline of how fast I can turn out good beer. Maybe after I get a head in my brewing I’ll be able to lower the PSI and see how if the flavor changes.

It really works a treat eh? Wondering... did you let it free-off-gas the first 12-24hrs before you applied the spund, or let it rise to 25-30 PSI right from yeast pitch?

I've been doing the former in the thought it would work thru the initial "high temp" flavors that lager yeast can generate, then apply pressure for the remainder of the fermentation. I'm topping out at 12-15 PSI usually cuz I'd heard higher pressures can depress yeast performance, but I'm starting to think that's a bit overblown for my homebrew needs.

Cheers!

 

[humpadilo]

It really works a treat eh? Wondering... did you let it free-off-gas the first 12-24hrs before you applied the spund, or let it rise to 25-30 PSI right from yeast pitch?

I've been doing the former in the thought it would work thru the initial "high temp" flavors that lager yeast can generate, then apply pressure for the remainder of the fermentation. I'm topping out at 12-15 PSI usually cuz I'd heard higher pressures can depress yeast performance, but I'm starting to think that's a bit overblown for my homebrew needs.

Cheers!

Yeah, I just keep my spunding valve at about 25-30 and put it on my fermenter as soon as I transfer it from my brew pot. I usually get the temp down to 75-80 in my brew pot. I’m in Texas, so the ground water doesn’t get to cold.

 

[DuncB]

I suppose the open ferment duration is influenced a bit by the yeast you use. If you were using a clean kveik at say 28celsius you might miss the boat for your pressure ferment if you wait 24 hours. You'd then just be in time for a spunding to carbonate stage. I think those high temp off flavours are meant to be suppressed by the pressure so why wait?
I haven't seen the yeast struggle under pressure, even when I accidentally had my spunding valve wrong and the wheat beer was at 35 psi when I discovered my error. It was still bubbling away at that pressure, but was a long process to de gas it to a lower level without it foaming out of the fermenter.