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Fermenting under pressure

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This is a learning platform. I am open to people coming forward and hopefully opening my mind to new ideas.
QUOTE="phildo79, post: 1010392, member: 10037
I can also ferment at a specific psi, depending on temperature, to get a more accurate carbonation level for the style of beer.
[/QUOTE]
I would say though that, as for the correct carbonation levels for the style of beer. You can achieve correct carbonation and monitor the psi in relation to temperature with most keg set ups with a Co2 regulator and some way of cooling the beer. I can do this with my 10litre keg set up from dark farms and my fridge. This has nothing to do with pressure fermentation.
My argument also stands, are we saying that all commercial breweries and craft beer micro breweries, of which there are countless that don’t use pressure fermentation methods, serving beers that lack aroma and flavour? I think they can do this without pressure fermentation. You can achieve this at home too.
 
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foxy

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My beers used to lose aroma and flavour fast. I now ferment under pressure and close transfer. My beers no longer lose aroma and flavour. I can also ferment at a specific psi, depending on temperature, to get a more accurate carbonation level for the style of beer. There are a good few benefits to using them. I've only had mine about six months but I love it. Best piece of brewing kit I have bought.
Why would pressure fermenting prevent losing aroma and flavour? The venting gas will still be taking with it hop aroma and flavour at the same rate as if fermenting with a piece of cling film over the top of a fermenting vessel. I have done both the only thing I could give the thumbs up to is mouth feel from using the co2 from fermentation to carbonate my beer. Now I don't know why this is so, because theoretically it should be no different to priming a keg or a bottle with sugar and letting the yeast carbonate the beer. Same thing right?
While still extremely drinkable an ale under pressure loses its character. I am sure this would be picked up by qualified BJCP tasting it. If pressure fermenting was so good, every man and his dog would be doing it. Respected writers don't mention it, though I suspect George Fix would have something to say about it if he wasn't the wrong side of the grass. Pro brewers don't advocate it.
Scott Janish, I respect his views, he backs a lot of what he says with qualified research, unlike Marshall Schott who makes a good living on the side from the home brewers who read his blogs.
After saying this if you are happy with what you are producing by pressurising the vessel from the start keep doing it, but don't lay claim that it makes a better beer or even lager. It doesn't.
Just try doing it as Teri Fahrendorf suggested. She is far more knowledgeable than some pleb who took her PDF off on an entirely different tangent, I know I would far sooner take note of someone qualified in their trade than a drovers dog.
 

DocAnna

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I have concerns about the web articles referenced in that they reflect single instance fermentation trials and subjective assessments in most cases, or where a more experimental methodology has been used, this hasn't been against a suitable control, and hasn't been published in a peer review journal. Yes I am an academic snob by such standards.. I like meta-analyses in peer reviewed journals, or at least controlled methodology. So I went looking (as usual)... and this has been looked at before quite a while ago. There is also a lot of literature about fermenting under pressure for industrial alcohol production from wood type pulp due to the acceleration of alcohol production - not quoted here but interesting to note. I'm quoting abstracts here but I did read the papers properly, my comments are in italics.

Yes the effect of pressure is to reduce the overall amount of yeast growth and reduces higher alcohols and esters:

Renger, R. S, Hateren, S. H. van & Luyben, K. Ch. A. M, 1992. THE FORMATION OF ESTERS AND HIGHER ALCOHOLS DURING BREWERY FERMENTATION; THE EFFECT OF CARBON DIOXIDE PRESSURE. Journal of the Institute of Brewing, 98(6), pp.509–513.
The influence of the size and geometry of brewery fermentation vessels on beer flavour and aroma formation is generally attributed to carbon dioxide pressure. In order to study this pressure effect, brewery batch fermentations were carried out on the laboratory scale with Saccharomyces cerevisiae. The formation rates and yields of esters and fusel alcohols were studied in relation to the growth of metabolically active biomass. The results indicate that the observed reduction in the formation of esters and fusel alcohols with increased carbon dioxide pressure is mainly caused by reduced yeast growth. The overall formation of fusel alcohols is less affected than the formation of esters.​

Anyone worried about high pressure slowing down fermentation - nope, gets faster right up until about 1500 psi, you have to get above 12000psi (yes twelve thousand!) before alcohol production stops.

Picard, A et al., 2007. In situ monitoring of alcohol fermentation by Saccharomyces cerevisiae under high pressure by quantitative Raman spectroscopy. Extremophiles : life under extreme conditions, 11, pp.445–452.
We monitored alcoholic fermentation in Saccharomyces cerevisiae as a function of high hydrostatic pressure. Ethanol production from 0.15 M glucose was measured by Raman spectroscopy in situ in a diamond-anvil cell. At 10 MPa, fermentation proceeds three times faster than at ambient pressure and the fermentation yield is enhanced by 5% after 24 h. Above 20 MPa, the reaction kinetics slows down with increasing pressure. The pressure above which no more ethanol is produced is calculated to be 87 ± 7 MPa. These results indicate that the activity of one or several enzymes of the glycolytic pathway is enhanced at low pressure up to 10 MPa. At higher pressures, they become progressively repressed, and they are completely inhibited above 87 MPa. Although fermentation was predicted to stop at ca. 50 MPa, due to the loss of activity of phosphofructokinase, the present study demonstrates that there is still an activity of ca. 30% of that measured at ambient pressure at 65 MPa. This study also validates the use of Raman spectroscopy for monitoring the metabolism of living microorganisms.​
Real world application in commercial lager beer making setting, 16 deg C at 26 psi roughly equivalent to 10 deg and 15 psi for alcohol and ester production.

Landaud, Sophie, Latrille, Eric & Corrieu, Georges, 2001. Top Pressure and Temperature Control the Fusel Alcohol/Ester Ratio through Yeast Growth in Beer Fermentation. Journal of the Institute of Brewing, 107(2), pp.107–117.
Temperature and top pressure are key factors for maintaining a consistent quality of lager beer. Their influence on yeast growth, CO2 production, final concentrations of fusel alcohol and ester and production kinetics was analysed under industrial conditions. Fermentations of 12°P lager wort were performed at 10°C or 16°C temperature and 1.05 bars or 1.8 bars top pressure, corresponding to dissolved carbon dioxide concentrations of 1.98 g/litre to 3.65 g/litre. Analysis of variance was performed to test the significance of temperature and dissolved C2. Results show that temperature increases fermentation rate and the production ratio and final concentration of fusel alcohol, independently of the top pressure applied. Conversely, dissolved carbon dioxide controls the production rate and final concentration of ester by limiting yeast growth. Relationships between initial or maximum ester production rates and maximal growth rates were shown. Considering the metabolic pathways occurring during anaerobic growth of yeast, a limited production of acetyl CoA was expected in cultures with high concentrations of dissolved carbon dioxide. Also, final ester concentration and biomass produced are linearly correlated. Furthermore, whatever the ester considered, its synthesis is not influenced by corresponding fusel alcohol availability.​
It was demonstrated that fermentations performed with a reasoned combination of temperature and top pressure can result in a beer of distinctive aroma without resorting to modification of the initial wort or yeast strain.​
Anna​
 
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I have concerns about the web articles referenced in that they reflect single instance fermentation trials and subjective assessments in most cases, or where a more experimental methodology has been used, this hasn't been against a suitable control, and hasn't been published in a peer review journal. Yes I am an academic snob by such standards.. I like meta-analyses in peer reviewed journals, or at least controlled methodology. So I went looking (as usual)... and this has been looked at before quite a while ago. I'm quoting abstracts here but I did read the papers properly, my comments are in italics.

Yes the effect of pressure is to reduce the overall amount of yeast growth and reduces higher alcohols and esters:

Renger, R. S, Hateren, S. H. van & Luyben, K. Ch. A. M, 1992. THE FORMATION OF ESTERS AND HIGHER ALCOHOLS DURING BREWERY FERMENTATION; THE EFFECT OF CARBON DIOXIDE PRESSURE. Journal of the Institute of Brewing, 98(6), pp.509–513.
The influence of the size and geometry of brewery fermentation vessels on beer flavour and aroma formation is generally attributed to carbon dioxide pressure. In order to study this pressure effect, brewery batch fermentations were carried out on the laboratory scale with Saccharomyces cerevisiae. The formation rates and yields of esters and fusel alcohols were studied in relation to the growth of metabolically active biomass. The results indicate that the observed reduction in the formation of esters and fusel alcohols with increased carbon dioxide pressure is mainly caused by reduced yeast growth. The overall formation of fusel alcohols is less affected than the formation of esters. There is also a lot of literature about fermenting under pressure for industrial alcohol production from wood type pulp due to the acceleration of alcohol production - not quoted here but interesting to note.​

Anyone worried about high pressure slowing down fermentation - nope, gets faster right up until about 1500 psi, you have to get above 12000psi (yes twelve thousand!) before alcohol production stops.

Picard, A et al., 2007. In situ monitoring of alcohol fermentation by Saccharomyces cerevisiae under high pressure by quantitative Raman spectroscopy. Extremophiles : life under extreme conditions, 11, pp.445–452.
We monitored alcoholic fermentation in Saccharomyces cerevisiae as a function of high hydrostatic pressure. Ethanol production from 0.15 M glucose was measured by Raman spectroscopy in situ in a diamond-anvil cell. At 10 MPa, fermentation proceeds three times faster than at ambient pressure and the fermentation yield is enhanced by 5% after 24 h. Above 20 MPa, the reaction kinetics slows down with increasing pressure. The pressure above which no more ethanol is produced is calculated to be 87 ± 7 MPa. These results indicate that the activity of one or several enzymes of the glycolytic pathway is enhanced at low pressure up to 10 MPa. At higher pressures, they become progressively repressed, and they are completely inhibited above 87 MPa. Although fermentation was predicted to stop at ca. 50 MPa, due to the loss of activity of phosphofructokinase, the present study demonstrates that there is still an activity of ca. 30% of that measured at ambient pressure at 65 MPa. This study also validates the use of Raman spectroscopy for monitoring the metabolism of living microorganisms.​
Real world application in commercial lager beer making setting, 16 deg C at 26 psi roughly equivalent to 10 deg and 15 psi for alcohol and ester production.

Landaud, Sophie, Latrille, Eric & Corrieu, Georges, 2001. Top Pressure and Temperature Control the Fusel Alcohol/Ester Ratio through Yeast Growth in Beer Fermentation. Journal of the Institute of Brewing, 107(2), pp.107–117.
Temperature and top pressure are key factors for maintaining a consistent quality of lager beer. Their influence on yeast growth, CO2 production, final concentrations of fusel alcohol and ester and production kinetics was analysed under industrial conditions. Fermentations of 12°P lager wort were performed at 10°C or 16°C temperature and 1.05 bars or 1.8 bars top pressure, corresponding to dissolved carbon dioxide concentrations of 1.98 g/litre to 3.65 g/litre. Analysis of variance was performed to test the significance of temperature and dissolved C2. Results show that temperature increases fermentation rate and the production ratio and final concentration of fusel alcohol, independently of the top pressure applied. Conversely, dissolved carbon dioxide controls the production rate and final concentration of ester by limiting yeast growth. Relationships between initial or maximum ester production rates and maximal growth rates were shown. Considering the metabolic pathways occurring during anaerobic growth of yeast, a limited production of acetyl CoA was expected in cultures with high concentrations of dissolved carbon dioxide. Also, final ester concentration and biomass produced are linearly correlated. Furthermore, whatever the ester considered, its synthesis is not influenced by corresponding fusel alcohol availability.​
It was demonstrated that fermentations performed with a reasoned combination of temperature and top pressure can result in a beer of distinctive aroma without resorting to modification of the initial wort or yeast strain.​
Anna​
Hi,
Nice work tracking that all down for us.
Genuinely interesting.
Thanks
 

DocAnna

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Just to add that my take away from all of this is that higher pressure at higher temperature can be equivalent to lower temperature at no additional pressure, quite what temperature and pressure isn't clear. For me, this means for a lager, ferment at 15-26 psi at a higher temp than I would normally, 16-18 deg. For all others, ferment at v low, less than 5psi effectively using the spunding valve as an airlock, then after most of fermentation is done, set to the pressure for carbonation reasons rather than flavour. Oddly enough, other than for lager, that's pretty much what Teri Fahrendorf suggested in the first place 😆!

Anna
 

phildo79

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Why would pressure fermenting prevent losing aroma and flavour?
It doesn't. The closed transfer between the vessels prevents it. Fermenting under pressure means I don't have to faff around after the transfer is complete. The snubnose has the ability to carbonate the beer quite accurately for the style, so I take that advantage.
 

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I would be interested to hear if anyone has given fermenting under pressure a real go and given it up as detrimental or pointless.

On the plus side the equipment was cheap and it's pretty easy. I'm certainly looking forward to replacing my syphoning and bottling with closed transfer to a single keg.

Upgrading my equipment and embracing new techniques is giving me a lot of enjoyment at the moment. Not all going smoothly but I'm getting there.
 

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Just to stick my oar in...

If you are a member of home brewing FB groups, they seem to be populated by eager new brewers with their shiny new Fermzillas who think pressure fermenting (a phrase I actively dislike as it suggests its the pressure that does the fermentation) is a magical path to beer valhalla. One guy questioned why his best bitter (which he fermented at 15 PSI) tasted bland 🧐

What is a pressurised FV good for:

- Making lagers at ale temps
- Carbonating beer in the FV as fermentation comes to an end
- Closed transfers

Anything else? No
 

Brewnaldo

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Just to stick my oar in...

If you are a member of home brewing FB groups, they seem to be populated by eager new brewers with their shiny new Fermzillas who think pressure fermenting (a phrase I actively dislike as it suggests its the pressure that does the fermentation) is a magical path to beer valhalla. One guy questioned why his best bitter (which he fermented at 15 PSI) tasted bland 🧐

What is a pressurised FV good for:

- Making lagers at ale temps
- Carbonating beer in the FV as fermentation comes to an end
- Closed transfers

Anything else? No
Bit of horses for courses here then really, because the bold is invaluable to me. So for all the "but why would you even do that!?" type ont he thread, that's exactly why I do it, with the second two points also being pretty relevant also.
 

BlackRegent

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Bit of horses for courses here then really
Agree with you 100%. I'm not against using a pressurisable FV and my main FV is a snubnose. I just think it's a shame they seem to be commonly misunderstood and they can't deliver what many people expect of them.
 

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I don't pressure ferment but I do control the fermentation gases keeping the system (almost) closed. Gas from a lidded fermentation bucket is either collected in balloons (used during cold crash) or vented through a bubbler. I fill my King Keg with water and displace it with CO2 from a cylinder. My FV has a bottom tap with a float tube inside. Connecting the FV tap to the beer out connection on my keg allows beer to flow and push the CO2 out of the keg's gas in connection back through a pipe connected to the lid of the FV. 5 gallons transfers in between 40 and 60 minutes. No pressure just gravity.
 

phildo79

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What is a pressurised FV good for:

- Making lagers at ale temps
- Carbonating beer in the FV as fermentation comes to an end
- Closed transfers

Anything else? No
It's a multi-function FV, i.e. you can also use it as a standard FV if you wish.
You can produce finished beer quicker.
You can harvest yeast easier.
You can see exactly what is going on inside it.
You can not only carbonate the beer but dial in the carbonation level.
 

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My 2 pence worth, there shouldn't be a need to debate them, they're just another tool available to brewers, and like any tool you have to use it correctly. If you put a screw in using a hammer, that's not what a hammer is for....

Also, like everything, for almost every pro, there's a con. Ignoring the fact that not all pressure FVs are PET for a moment... You can see exactly what is going on inside it, yup the con of that is it's exposing the contents to light, which means you have to either put a jacket on it, cover it in some way, put it in a dark cupboard or put it in a fridge (uhm, so, yeah now you have temperature control anyway, so could probably make lagers at lager temps anyway... lol). Oh and woe betide you if you put anything too hot into a PET container.... ;) Suddenly your FV is Morph! :D

You can harvest yeast easier, uhm, yeah you can do that on all conicals with a bottom tap thingy, not just pressure FVs. Just don't do it with the beer still in there though, bloop. lol

Produce finished beer quicker, not heard of kveik yet then? ;)

As to carbonating, yeah ok, another tool for that then.

It just isn't the bee's knees is all, and certainly has a place in the hobby for sure (fairly sure it's made producing NEIPAs a LOT easier for example, along with closed transfer). There's no need to decry it, or announce it as the saviour of the hobby. It's just there, for those who want to play with it.
 
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I don’t think anyone is debating how good a fermzilla style FV is. The debate is not over the benefits of seeing what is going on inside the FV and the ease of yeast harvesting etc etc. All very good pros for a great bit of kit.
We must remember though that it’s the skilled brewer that is making great beer and not the kit. The skilled brewer can and will make fantastic beer in a cheep plastic fermentation bin and serve it to you from a 20 year old plastic king keg.
Because brewing fantastic beer is about knowledge, skill and patience and not about owning the next best and expensive thing on the market..
Anyhoo..
So the debate is about pressure fermentation.
Is it the future? Does it produce better or comparably good results? I am certainly up for trying it and comparing it to my old tried and tested methods.
 

Leon103

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Why would pressure fermenting prevent losing aroma and flavour? The venting gas will still be taking with it hop aroma and flavour at the same rate as if fermenting with a piece of cling film over the top of a fermenting vessel. I have done both the only thing I could give the thumbs up to is mouth feel from using the co2 from fermentation to carbonate my beer. Now I don't know why this is so, because theoretically it should be no different to priming a keg or a bottle with sugar and letting the yeast carbonate the beer. Same thing right?
While still extremely drinkable an ale under pressure loses its character. I am sure this would be picked up by qualified BJCP tasting it. If pressure fermenting was so good, every man and his dog would be doing it. Respected writers don't mention it, though I suspect George Fix would have something to say about it if he wasn't the wrong side of the grass. Pro brewers don't advocate it.
Scott Janish, I respect his views, he backs a lot of what he says with qualified research, unlike Marshall Schott who makes a good living on the side from the home brewers who read his blogs.
After saying this if you are happy with what you are producing by pressurising the vessel from the start keep doing it, but don't lay claim that it makes a better beer or even lager. It doesn't.
Just try doing it as Teri Fahrendorf suggested. She is far more knowledgeable than some pleb who took her PDF off on an entirely different tangent, I know I would far sooner take note of someone qualified in their trade than a drovers dog.
What are the proper homebrewers doing on the proper homebrew forums?
If people want to pressure ferment, let then, who cares. In fact you say you also do it, why do you do it?
 

Leon103

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I don’t think anyone is debating how good a fermzilla style FV is. The debate is not over the benefits of seeing what is going on inside the FV and the ease of yeast harvesting etc etc. All very good pros for a great bit of kit.
We must remember though that it’s the skilled brewer that is making great beer and not the kit. The skilled brewer can and will make fantastic beer in a cheep plastic fermentation bin and serve it to you from a 20 year old plastic king keg.
Because brewing fantastic beer is about knowledge, skill and patience and not about owning the next best and expensive thing on the market..
Anyhoo..
So the debate is about pressure fermentation.
Is it the future? Does it produce better or comparably good results? I am certainly up for trying it and comparing it to my old tried and tested methods.
I have never had a fantastic neipa out of a plastic pb. I did ask the last time I was at Verdant if they had any neipa's in a pb but sadly not. Couldn't work out why
 

Brewnaldo

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I don’t think anyone is debating how good a fermzilla style FV is. The debate is not over the benefits of seeing what is going on inside the FV and the ease of yeast harvesting etc etc. All very good pros for a great bit of kit.
We must remember though that it’s the skilled brewer that is making great beer and not the kit. The skilled brewer can and will make fantastic beer in a cheep plastic fermentation bin and serve it to you from a 20 year old plastic king keg.
Because brewing fantastic beer is about knowledge, skill and patience and not about owning the next best and expensive thing on the market..
Anyhoo..
So the debate is about pressure fermentation.
Is it the future? Does it produce better or comparably good results? I am certainly up for trying it and comparing it to my old tried and tested methods.
I'm putting a lot of stock in terms of my pressure experimenting on the brew I currently have in it. Due to leaks which I resolved, and subsequent swings in pressure (I wont get into this, suffuce to say my methods weren't in line with best/safest practice) and some temps swings, I am going to say that if this lager comes out good, then pressure fermenting is at the very least, the best way to make lager without a fridge, but going by the sample in the jar I took lastnight, it might be a credible way to make the best lager you can full stop. That's a bold claim, and I will follow it up with a cold fermented one for my own comparison, but without a brew fridge I am running out of time for this with the weather.

I'm not married to my pressure FV and I will try to remember to update this thread in a couple of weeks when its bottled/kegged and do so honestly, but I really do have high hopes as far as ease of creating a really goo, clean lager goes
 
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I have never had a fantastic neipa out of a plastic pb. I did ask the last time I was at Verdant if they had any neipa's in a pb but sadly not. Couldn't work out why
Oh I am sorry. You seem to have missed the point of what was being said. It must have past you by when you were coming up with that zinger. Sorry that “Verdant” didn’t have any good pb neipa for you. Shame that. 😉
 
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