Fermenting Under Pressure

[Greg Donohue]

On the right track but not as simple as that, 2 days of a vigorous ferment gets the unwanted elements from the beer evacuating with the co2. Cap the ferment using a spunding valve and pressurise the beer.
Now you come to the tricky bit, you can't just put a pressurised vessel into a cold crash, I think someone on a thread here posted a pic of their s/steel fermenter which was sealed and the lid sucked in due to the co2 being drawn back into the beer, put your snub nose in, leave it for about 20 mins and you will see what I mean. I counteracted this by putting an expandable plastic water bottle filled with co2 connected to the gas post of the fermenter, so as the gas is drawn into the beer it is replaced by the gas I had collected. Or you could just use gas from a bottle.


And there are even more not pressure fermenting. Terri Fahrendorf a brewer, laid out solid ground rules for carbonating under pressure. Which is what almost all the pro brewers do to carbonate their beers.

Please do a bit of homework .
If you ferment at a decent pressure which is self carbonation this will not happen .
My pressure drops about .3 of a bar or 4psi
After i cold crash .
Never in a million year's will it implode .

 

[TheSumOfAllBeers]

If you need to hop your pressure fermented beers consider using a randalling device, and pumping the beer through it across the disconnects.

 

[wide eyed and legless]

Please do a bit of homework .
If you ferment at a decent pressure which is self carbonation this will not happen .
My pressure drops about .3 of a bar or 4psi
After i cold crash .
Never in a million year's will it implode .

If you had taken the time to read my previous posts, you would have seen that the maximum pressure I went to was 2 psi, and you can take my word for it if a breather isn't attached, the PET fermenters will suck in. As you stated your pressure drops 3-4 psi that leaves mine as a negative 1-2 psi.

 

[Greg Donohue]

If you had taken the time to read my previous posts, you would have seen that the maximum pressure I went to was 2 psi, and you can take my word for it if a breather isn't attached, the PET fermenters will suck in. As you stated your pressure drops 3-4 psi that leaves mine as a negative 1-2 psi.

My bad .
Apologies .
Why would you only go to 2psi?

 

[wide eyed and legless]

My bad .
Apologies .
Why would you only go to 2psi?

I like to keep the esters of the yeast, I brew mainly English style beers, the lower pressure keeps the esters in tact. If I was brewing an AIPA I would be tempted to go higher as they are more hop forward.

 

[Half-baked]

Hi WEAL, to turn the question around, what are the benefits of fermenting at 2 PSI vs no pressure?

 

[wide eyed and legless]

Hi WEAL, to turn the question around, what are the benefits of fermenting at 2 PSI vs no pressure?

Ensuring I get no oxygen during transfer, the best advice is what Kiene _ahnung said in post 672. He is a brewer and not going to give out duff advice.
Another thing I find strange is, all the respected writers on brewing has never come out and given endorsements on fermenting under pressure. Some time ago I emailed John Palmer about pressurised fermentation, he replied, 'Why would anyone do that'.

 

[bruiserbbq]

I noticed that Russian River’s new brewery has pressure fermenters....so they must think it beneficial!

 

[wide eyed and legless]

I noticed that Russian River’s new brewery has pressure fermenters....so they must think it beneficial!

They are all pressure fermenters capable of 15 PSI minimum used for carbonating as described by Terri Fahrendorf

 

[FarsideOfCrazy]

I noticed that Russian River’s new brewery has pressure fermenters....so they must think it beneficial!

All of the 3 micro's near me have pressure rated vessels. They're pressure rated for transferring and carbing.

My favourite micro has 3000litre and 6000litre fermenter and bright tanks. I've done a couple of brew days with him and asked a lot of questions. When we spoke about pressure fermenting he said it is not something to do as it stresses the yeast. The only time he said to use a spunding valve was when there is a couple of points left to build some transfer pressure. He knows of no pro brewers who pressure ferment.

This fermenting under pressure that home brewers are trying is not the same as what's happening in a big tall vessel.

They all carb the beer from tank c02 and not from spunding.

 

[keine_ahnung]

Ok.
One of these days I'm going to write an article about what actually happens inside the yeast cell, which hopefully helps people to understand how, when and why various fermentation biproducts are produced.
As our professor in fermentation always said "Once you understand how the yeast ticks, then you can really hone in on your fermentation".

...but that will have to wait a bit as I'm currently in the thick of studying for masters exams.

Note: the following applies strongly to lager yeast. However ale yeast still *works* the same, however due to much higher levels of fermentation byproducts in general, the effects described below are much less "noticeable" in ales.

IN SHORT:
the benefits of fermenting under pressure?
The essence of this question for me is: why?
Why deliberately put a living organism that is trying to metabolise energy sources (Glucose, Fructose, Saccharose, Maltose, Maltotriose) under extra stress *i.e. pressure?
(-> Would you like someone pressurising the restaurant while you're having dinner????? The yeast is also just eating, in order to have energy to reproduce itself <-)

Reason:
In industry breweries: TIME = $$$$

Now we all know: Warmer fermentation = faster fermentation
(plus numerous other factors like Oxygen levels, free amino acids, etc. But I won't go into that for now)

Problem:
Faster/warmer fermentation* = higher production of (most) byproducts. Well, apart from Esters....which are quite important/positive for flavour/aroma/texture of the beer.
*pitch temperature is actually more critical. But let's just generalise to overal fermentation temps for now...

Industry dilemma:
I've got 10 x 1000 Hectolitre tanks, and each one of them cost me $250,000. We currently brew 8 batches a week. If I can push each batch through in 6 days instead of 7 days, I can brew, say, 10 batchs a week -> fully utilising my capacity. I can make more/save money and pay off my tanks quicker. (Start thinking about the fact that in big breweries if a beer is "finished" on a saturday..........???????? Leave it sitting there over the weekend and risk autolyse, or pay overtime rates for workers on weekends. We're not just talking costs from capacity increase, but also massive logistical consequences on this scale)

I digress.. :!

Industry solution:
If I can somehow still ferment faster, but minimise the drawbacks that come with a warmer/faster fermentation, and still make a product that is "good enough" -> it's well worth it.
Which is why so many big breweries utilise pressure fermentation.

They know they could make a "better" beer, with more time and cooler fermentation temps (better balance of Esters:higher alcohols). And the level of attention that needs to be paid to such fast and "hectic" fermentations is considerably higher (breweries of this size have their own laboratories where they constantly analyse diacetyl levels and yeast health, etc etc)
But... financially, it's worth their while.
At the end of the day, even among hobby brewers, professional brewers, highly trained Braumeisters and the average bloke at the pub..... we are all so heavily influenced by brands, designs, marketing and mates, that unfortunately the beer itself is rarely judged on it's own.
--> If the beer is only 85% as "good", but you sell 25% more of it: the CEO is happy!!!


So as I keep saying:
it's awesome that so many people want to brew great beer!
But often context is everything.
Russian River may well have pressure fermenters....sounds like it's becoming more and more trendy. However;

Some food for thought:
The beer that was in the cans that are often left under park benches and on trains.....there's a very high probability that those breweries have had pressure fermenters for years. Is that really your goal?

I'm not saying that all beer brewed under pressure is "bad". However when you talk to people who reeeeeeally understand yeast and fermentation, you realise that pressure fermentation was developed as shortcut to save time/money. Not as a means to make the best beer possible.


**Disclaimer: I admit there's still lots I'm yet to learn about brewing, especially in more exotic brewing cultures (e.g. in Belgium etc etc), and I've no doubt that lots of breweries make great beers under pressure. And I have no intention to rag on such breweries. I just want people to also understand that they usually have some very large aspects (financial feasibility) which don't apply to brewing in your garage

 

[MHB]

Pretty much covers it!

Worth remembering that way back when there was no bottled CO2 or good pressure rated tanks to brew in, the only way to get fizz into beer was naturally.
Lager brewers would cool the ferment slowly (0.5-1oC/day) from ferment to lagering temperatures, Lager yeast will keep fermenting at the temperature falls, the CO2 produced goes into solution maintaining the desired amount of dissolved CO2 - no sudden changes in temperature or pressure for the yeast to adapt to or to collapse tanks...

Crash chilling (often 10-20oC/day) is yet another attempt to speed up the process, rather than to improve it.
People say beer is made with Hops, Malt Water and Yeast, I would love to add Patience to that list.
Mark

 

[devoutharpist]

Very interesting reads. My main desire to pressurise is to reduce oxidation, not speed up the fermentation process. I've had a few heavily hopped beers turn to river water recently as my current process allows for a LOT of oxygen exposure. That said, it works perfectly fine for strong ales, stouts, belgians, etc.

For anyone that cares, i think i am going to try a blow-off valve until after the dryhopping, the swap a spunding in and build up pressure (maybe in the world of 5-6psi, additional CO2 if required) to counteract negative pressure and collapse. Cold crashing to drop the hops down to the bottom so they hopefully don't clog the balls out of the tubing when i pressure transfer to a keg.

 

[Half-baked]

Hi @devoutharpist and WEAL, am keen to understand the theory here.
Is it that at a higher pressure, more of the gas that will be absorbed is CO2, meaning despite the same overall amount of O2 less can be absorbed?
Or at a higher pressure, gases will stratify more and the O2 is more likely to be released through the spunding valve?
Or something else...
Thanks

 

[Fro-Daddy]

When you carbonate in the bottle with sugar, the same yeast is going through the stress of pressure - even more I would say.
Why isn't it a bad thing when bottling?
Is it less important/has less influence at the end of fermentation?

 

[Tony121]

I must say, this is the best discussion I’ve seen on this forum for a number of years.

 

[wide eyed and legless]

Hi @devoutharpist and WEAL, am keen to understand the theory here.
Is it that at a higher pressure, more of the gas that will be absorbed is CO2, meaning despite the same overall amount of O2 less can be absorbed?
Or at a higher pressure, gases will stratify more and the O2 is more likely to be released through the spunding valve?
Or something else...
Thanks

It isn't just the pressure that distresses the yeast, it is far more difficult to pressurise a liquid than it is a gas. So what happens, the co2 which is a bi-product of the yeast is not being vented, it is dissolving back into the wort, putting even more stress on the yeast.
Venting the co2 drives off any O2 along with other unwanted compounds from the beer.
For me nowadays, I send mine through either a secondary fermenter, or a cube which I use as a cask, I dry hop in both cases but in the cube I put a bout 2 desert spoons of sugar added to water which has been boiled transfer the beer where it will ferment again venting through an inline regulator so keeping some pressure. I have a 8psi inline regulater which is to high for a cask ale so I have given that one the Tijuana. I now use an adjustable one keeping it around 4 or 5 psi.

 

[wide eyed and legless]

When you carbonate in the bottle with sugar, the same yeast is going through the stress of pressure - even more I would say.
Why isn't it a bad thing when bottling?
Is it less important/has less influence at the end of fermentation?

I would say that because the process is complete, the yeast is being used solely to carbonate. Though it is a good point, to much sugar and they will keep munching through it until the bottle explodes

 

[Grok]

I would say that because the process is complete, the yeast is being used solely to carbonate. Though it is a good point, to much sugar and they will keep munching through it until the bottle explodes

This extract of an article about "Effect of High Pressures on Bacteria" from Oxford University Press might provide enlightenment!
https://www.jstor.org/stable/30080457?seq=3#metadata_info_tab_contents

Which leads me onto what I think should be an important question for consideration!
Is Pressure Fermenting actually better for yeast health?
If the the above info is true, then logical would suggest that healthy yeast is not damaged by beer brewing practices using pressurized vessels at all, indeed, according to this article here https://onlinelibrary.wiley.com/doi/pdf/10.1002/j.2050-0416.1898.tb00042.x , quite the opposite in fact!
Although it appears to be the results of a very old experiment, it is none the less relevant to this discussion I think.
I know from my own experience that I've used the same yeast over and over about up to 25 times with no washing or anything, and seemly no difference in fermenting vigor or flavours each time (in pressure fermenting of course!). I only changed because I wanted to try a some different yeasts.
It would be good to get peeps thoughts on this line of thinking!
Maybe this would be better as a new thread? Moderators?

 

[wide eyed and legless]

Well it is interesting that the two articles you have decided to offer up one is from The Journal Of Infectious Diseases. The other from a discussion held in 1898, with no scientific proof because the sun wasn't out on the day he wanted to take the photo's, I have read before that the Burton Union was a form of pressure fermenting, but it is very minimal pressure, my 2 psi would probably sound excessive.
Also in Wiley online there are varying articles of the amount of times yeast can be used, I have read that it can be used over and over and others have said it would best be limited to fewer times.
I could be wrong, but my theory is, in nature the usual occurrence when a species comes about either by design or by fluke, nature will rectify it. Meaning the said species will start to revert back to its original structure. Probably the only home brewer who could answer that would be Tracy Aquilla, he has a BS in microbiology and a PhD in Genetics.