Pressure fermentation set up right?

[gwind]

I bought a used homebrew kit online which included things for pressure fermentation. I did some research online and believe I have set it up correctly, but want to double check myself. I have my spunding value set to 0.6 brix (fermenting a lager with German Cellar Science yeast), have a PSI gauge, and a PRV for safety. There were a few parts to the fermenter set up that I did not use, mainly because I wasn't sure what they were for.
I'll be fermenting at 54 F. I have my thermometer probe attached to the outside of my fermentation tank and inside the insulated jacket. I have cold water set up in a fridge set to 51 F and a pump that will turn on when the fermenter needs to cool down. I didn't plug in my heating element.

 

[VikeMan]

A few thoughts...

- Brix is not a unit of pressure
- Fermenting at 54F and cooling with 51F water may be a challenge. Normally, you would want a bigger difference with most setups.
- Your temp probe is between the fermenter and the jacket... does the jacket also contain the cooling elements? If so, your probe readings are going to be too low.
- You might ask yourself why you want to ferment under pressure. If you have the ability to cool to normal lager fermentation temperatures, I don't see any advantage to pressure.

 

[Bassman2003]

My view of pressure fermentation is about amount of pressure vs desired outcome. It is all about clean beer or the amount of esters you want to create:

Warm fermentation, no pressure = a lot of esters.
Warm fermentation, low pressure - less esters.
Warm fermentation, high pressure = even less esters.
Cold Fermentation, no pressure = low esters.
Cold Fermentation, low pressure = lower esters.
Cold Fermentation, high pressure = almost no esters.

Low pressure = 5-10PSI High pressure = 20-30 PSI

You wouldn't brew a hefeweizen cold at 30PSI nor would you normally brew a lager warm at no pressure. Big breweries have larger tanks which naturally have hydrostatic pressure on the fermenting beer. Pressure fermentation at the homebrew scale is an attempt to emulate the big tank flavor. There is a slightly thicker mouthfeel associated with higher pressure as well which is nice.

In short, adding pressure reduces a lot of flavors (good and bad) in the final beer. It does limit VDK flavors which is a positive. It is a level to pull to get a desired outcome. But it does add more CO2 in solution which is tougher on the yeast. So you need to build up the pitch rate as the pressure increases.

 

[gwind]

A few thoughts...

- Brix is not a unit of pressure
- Fermenting at 54F and cooling with 51F water may be a challenge. Normally, you would want a bigger difference with most setups.
- Your temp probe is between the fermenter and the jacket... does the jacket also contain the cooling elements? If so, your probe readings are going to be too low.
- You might ask yourself why you want to ferment under pressure. If you have the ability to cool to normal lager fermentation temperatures, I don't see any advantage to pressure.

-I meant Bar. Set to 0.6 Bar which is about 8.7 PSI.
-I found that out this morning, set the fridge temp to 33 F.
-the jacket does not contain any cooling elements, just a heating sleeve but I have this turned off. I read that inbetween the fermentation vessel and jacket was the 2nd best spot if I could not have a temperature probe.
-I want to ferment under pressure to reduce esters, reduce chances of contamination, and ferment faster.

 

[VikeMan]

Big breweries have larger tanks which naturally have hydrostatic pressure on the fermenting beer.

While that's true, I'd say it's not as much as some people think, and IMO the impact is often overstated/overimagined. For example, a 20 feet tall fermenter adds only about 6 PSI more hydrostatic pressure than a 2 foot tall fermenter. And that's only at the bottom. At the top it's nothing. Compared to the kinds of headspace pressures some some brewers are adding, it's insignificant (IMO).

 

[gwind]

My view of pressure fermentation is about amount of pressure vs desired outcome. It is all about clean beer or the amount of esters you want to create:

Warm fermentation, no pressure = a lot of esters.
Warm fermentation, low pressure - less esters.
Warm fermentation, high pressure = even less esters.
Cold Fermentation, no pressure = low esters.
Cold Fermentation, low pressure = lower esters.
Cold Fermentation, high pressure = almost no esters.

Low pressure = 5-10PSI High pressure = 20-30 PSI

You wouldn't brew a hefeweizen cold at 30PSI nor would you normally brew a lager warm at no pressure. Big breweries have larger tanks which naturally have hydrostatic pressure on the fermenting beer. Pressure fermentation at the homebrew scale is an attempt to emulate the big tank flavor. There is a slightly thicker mouthfeel associated with higher pressure as well which is nice.

In short, adding pressure reduces a lot of flavors (good and bad) in the final beer. It does limit VDK flavors which is a positive. It is a level to pull to get a desired outcome. But it does add more CO2 in solution which is tougher on the yeast. So you need to build up the pitch rate as the pressure increases.

Thanks! I have read that only some yeast strands can survive in high pressure. The yeast I used does not say anything about pressure, so I'm going to assume it's not a high pressure yeast. https://cellarscience.com/products/german-dry-beer-yeast# Hence why I'm going to stick with low pressure (0.6 bar ~ 9 PSI)

Can you elaborate on building the pitch rate? Meaning add more yeast as the beer ages? Wouldn't I need to de-pressurize in order to do that? I started off with 2x 12g packets.

Also - when I checked my tank today my pressure gauge is still at 0. Does this mean my tank is not holding pressure and there may be a leak, or that the yeast has not started working yet? I'm doing a 5 gallon batch in a 15 gallon fermenter so there is quite a bit of headspace. There are also no bubbles in the spunding valvue.

 

[VikeMan]

-I found that out this morning, set the fridge temp to 33 F.

That should work much better.

-the jacket does not contain any cooling elements, just a heating sleeve but I have this turned off. I read that inbetween the fermentation vessel and jacket was the 2nd best spot if I could not have a temperature probe.

I would agree that if you don't have a thermowell, an insulated probe against the side of the fermenter is the next best thing.

-I want to ferment under pressure to reduce esters, reduce chances of contamination, and ferment faster.

For any given temperature, fermenting under pressure will generally result in less esters. But pressure slows down fermentation rather than speeding it up. (Again, for any given temp.) But I'm not sure why you think it will reduce chances of contamination. Do you have a scholarly source for that idea?

 

[VikeMan]

Can you elaborate on building the pitch rate? Meaning add more yeast as the beer ages? Wouldn't I need to de-pressurize in order to do that?

He means use more yeast at the normal pitch time.

Also - when I checked my tank today my pressure gauge is still at 0. Does this mean my tank is not holding pressure and there may be a leak, or that the yeast has not started working yet?

It could mean nothing significant has happened yet, or it could mean a leak. Both things are pretty common.

 

[gwind]

But I'm not sure why you think it will reduce chances of contamination. Do you have a scholarly source for that idea?

Not a scholarly source, but the idea I have heard a few times is that since the container is under pressure it is harder for contaminants to "get in" to the container. So reducing the risk of contamination while fermenting (albeit a low risk), not reducing the risk of contamination after the boil (probably where it's most likely to happen).
From https://hazyandhoppy.com/pressure-fermentation/

5. Reduced risk of contamination: Pressure fermentation can help to reduce the risk of contamination during the fermentation process, as the increased pressure can create a barrier that prevents airborne contaminants from entering the fermenter. This does not eliminate the need to sanitize your equipment!

 

[VikeMan]

Not a scholarly source, but the idea I have heard a few times is that since the container is under pressure it is harder for contaminants to "get in" to the container. So reducing the risk of contamination while fermenting (albeit a low risk), not reducing the risk of contamination after the boil (probably where it's most likely to happen).
From https://hazyandhoppy.com/pressure-fermentation/

Yeah, I'm not sure I'm going to buy that one, without data to support it. Once you reach the spunding valve's pressure setting, the rate of CO2 leaving the fermenter is about the same as the rate of CO2 leaving a non-pressurized fermentation. The pressure (per se) wouldn't stop bugs. What stops bugs is the "wind" from CO2 flowing out of the airlock (or spunding valve).

 

[Bassman2003]

While that's true, I'd say it's not as much as some people think, and IMO the impact is often overstated/overimagined. For example, a 20 feet tall fermenter adds only about 6 PSI more hydrostatic pressure than a 2 foot tall fermenter. And that's only at the bottom. At the top it's nothing. Compared to the kinds of headspace pressures some some brewers are adding, it's insignificant (IMO).

I can't say either way as I have not done any math myself. Your pressure number does seem smaller than others have mentioned. But, when I speak of large breweries I am thinking much larger than 20ft high tanks. But everything in this space is led by personal preference and experience. It is a lever to pull which offers something for homebrewers. For me, a 30PSI IPA ferment just tastes a lot better than the non-pressure ferments. Fun to experiment with but it is tough on the yeast. They can handle it but you need more of them from the start or the ferment will drag on and on.

 

[JohnDBrewer]

There is a slightly thicker mouthfeel associated with higher pressure......

Interesting, I've not heard this a feature of pressure fermenting.

 

[Bassman2003]

It only seems to show up with higher pressures. Some think it is an excretion from the yeast dealing with the more stressful environment.

 

[gwind]

I set the spunding valve to around 9 PSI and let the yeast create the pressure (I didn't add any myself). Pitched yeast Sunday night. Monday morning there was 5 PSI of pressure. I went a way on a trip and when I got back Wednesday night I noticed the PSI was at 0. I have a slow leak somewhere I'll need to investigate before my next batch. Temp was at 55 F for yeast pitching, then brought up to 65 F from Monday morning until now. Took gravity last night (Thursday) and was at 1.007 (where I want my FG). I figured I'd already done a diacyl rest since I was at 65 F for at least day (Wednesday night to Thursday night).
I did a diacyl test, I read here if you heat a sample to 140 F for 15 minutes, let it cool, then taste it and compare it to a non-heated sample, you'll be able to better identify diacyl. I've never done an off-flavor tasting, but the beer doesn't taste "good" and the warmed then cooled sample definitely tasted more buttery, so I'm assuming diacyl.
I moved my temp to 68 F and will keep it there and re-sample on Saturday (so 3 day diacyl rest). If I still taste the off-flavor, could it be a result of me loosing pressure too early into fermentation and the high temp and lager yeast creating off flavors? Is there anything I can do to "fix" this before cold crashing and laagering? My plan is to hope the flavor changes as I cold crash, then lager. Saturday into Sunday I plan to cold crash regardless of the taste then close transfer into a corny keg.
I'm brewing another batch on Sunday, do you think it's safe to re-use my yeast? i.e. the diacyl from this batch would be from off flavors produced by the yeast due to fermentation at too high temps w/o pressure too early, however I don't think that would make it so I couldn't re-use the yeast and the flavor would carry to the next batch. I know a general rule is don't transfer if there are off flavors, but this was fresh yeast I pitched. Also, morebeer was out of the yeast I ordered so my order for this weekend was delivered without yeast.

 

[VikeMan]

I moved my temp to 68 F and will keep it there and re-sample on Saturday (so 3 day diacyl rest). If I still taste the off-flavor, could it be a result of me loosing pressure too early into fermentation and the high temp and lager yeast creating off flavors?

Doubtful. I don't think there's a lot of data on diacetyl IRT pressure fermentation, but I've seen at least one study suggesting that pressure actually increases diacetyl levels and other claims (not sure if supported by data) that it makes no difference. But I've seen nothing at all suggesting that pressure reduces diacetyl. Also, fermenting lager yeast at higher temps (as an independent variable) has never been known (AFAIK) to cause increased diacetyl.

 

[IDMaynard]

Here is a pod cast from White Labs on Pressure Fermentation
https://www.masterbrewerspodcast.com/230
Here is an article in BYO magazine (subscription requested) (data set from White Labs)
https://byo.com/article/fermenting-under-pressure/
Here are the graphical results of the article above.

 

[Bassman2003]

Thanks. What does the "Lager" represent on the graph? It is like negative pressure or something as one can lager at 2 bar.

 

[IDMaynard]

Thanks. What does the "Lager" represent on the graph? It is like negative pressure or something as one can lager at 2 bar.

Lager represents a standard lagering profile (low temp at atmospheric pressure.) Zero pressure would be at ale temp (68 F) and atmospheric pressure, the last two are at 68 F and 15 psi (1 bar), then 68 F and 28 psi (2 bar). To clear up the charts, the y-axis is ppm of the item present, and the x-axis is fermentation pressure

 

[Bassman2003]

Thanks. I think it is kind of lame that they do not have a normal cold fermentation temp lager represented with pressure.

 

[IDMaynard]

Thanks. I think it is kind of lame that they do not have a normal cold fermentation temp lager represented with pressure.

But the whole purpose of pressure fermentation is to ferment lagers at ale temps without the side effects of high temperature fermentation (esters & diacetyl). I use my pressure fermentation as a method to carbonate my ales when they are nearing the end of the fermentation process. I seal up the system a few gravity points above final and let that CO2 dissolved into solution. My system is pretty much limited to 15 psi so I always have to do a little forced carbonation at the end but it is quicker to do since it is already partially carbonated.

 

[VikeMan]

But the whole purpose of pressure fermentation is to ferment lagers at ale temps without the side effects of high temperature fermentation (esters & diacetyl).

Where is there any evidence for lager strain fermentations at ale temps causing an increase in diacetyl? Esters, yes. Diacetyl? No evidence AFAIK.

 

[Chorgey]

I use my pressure fermentation as a method to carbonate my ales when they are nearing the end of the fermentation process. I seal up the system a few gravity points above final and let that CO2 dissolved into solution.

This is exactly what I do! Works great!

 

[Bassman2003]

But the whole purpose of pressure fermentation is to ferment lagers at ale temps without the side effects of high temperature fermentation (esters & diacetyl). I use my pressure fermentation as a method to carbonate my ales when they are nearing the end of the fermentation process. I seal up the system a few gravity points above final and let that CO2 dissolved into solution. My system is pretty much limited to 15 psi so I always have to do a little forced carbonation at the end but it is quicker to do since it is already partially carbonated.

That is one use but I would disagree about pressure fermentation = higher temperatures. I think you are being too narrow in your thinking about pressure fermentation. Fermenting lagers at 2 bar @ 50F makes an incredible beer. Just like fermenting IPAs at "normal" ale temps at 2 bar. Pressure is a tool or lever and it can be used in a variety of ways. Making lagers at high temps is a workaround for using less yeast or breweries to save money on throughput or capacity. It is not necessarily the best way. Homebrewers do not have to use a workaround if they choose not to.