Pressure fermenting impact on flavour

[hoppyscotty]

I am led to believe that pressure fermenting can suppress esters and flavour you get from yeast, which is a disadvantage as far as I'm concerned...however I wondered if you did the first half of fermentation without any pressure then for the second half attached the spending valve and let the pressure rise would the yeast esters have already formed in the first part of the un-pressurised fermentation?

I'm considering this as I want the benefit of carbonation in the fermenter. I'm convinced bottle conditioning results in a nicer and smoother carbonation for some reason...maybe smaller bubble or something, and now I don't bottle I want that in my kegs. I could condition in the kegs but would prefer to carbonate in the fermenter, which I am hoping provides a similar result to bottle conditioning, then keg the carbonated beer while preserving any flavour contribution from the yeast.

Thanks.

 

[stripeyjoe]

Here's an article on just that very topic!
https://edis.ifas.ufl.edu/publication/FS379

 

[hoppyscotty]

thanks for that, it's interesting but not sure it answers my specific question about the production of Esters from yeast under pressure. I've done a bit of googling and found some material that suggests the yeast esters are produced int he first 36hrs of fermentation. If that is the case then I can start spunding after 36hrs or so, so as not to suppress yeast esters in beers where it is desirable but yet still achieve carbonation, which sounds like a plan. think I'll give it a whirl and see what I get.

I guess the next challenge will be to determine what pressure and temperature to ferment at so when I cold crash I end up with the desired level of carbonation.

 

[stripeyjoe]

Did answer the bit about bubble size, that's what I googled as I was intrigued to see if carbonation method affected bubble size or not.

 

[hoppyscotty]

Ah yes thanks. That confirms my experience that I notice a difference between naturally carbonated beers and force carbonated beer. Beer is beer at the end of the day but I have a pressure capable fermenter and just sussing out the best way to use it to achieve the results I want.

 

[Rodcx500z]

Hi Hoppy i have 2 all rounders, i have done 2 brews in each, what i do is put 10psi in then put the spunding valve with the yellow bit all the way in i then open it when it gets to 5 psi i set so it stays at 5, after 4 days i increase it to 10psi, when i transfer i fill the keg and anything left i use a party tap to fill my glass, i have not noticed any difference in taste i don't know if it is right or wrong i have not researched pressure fermenting yet

 

[hoppyscotty]

Thanks Rod...I'm where you are in that I'm still trying to suss out what the point is or benefit is of pressure fermenting. I get it if you don't have temperature control so might want to be able to ferment hot, but I have a fermentation cabinet and I like the flavours I get from various yeasts and don't want to suppress that but see the carbonation appealing as a slight saving of CO2.

I know that the purity laws in Germany forbid even force carbonating with CO2 so they tend to pressure ferment for carbonation, but they tend to do lager styles with little flavour coming from the yeast (sure there are exceptions) so probably not so much of an issue for them.

I'm amazed how little information there is around about the technicalities of it. I was expecting a table to show pressure vs temperature for different yeasts for the different type of results, similar to carbonation charts or other calculators you can find for other things and even on alot of the yeast manufacturers websites they don't seem to have a huge amount of advice or information on how to pressure ferment their yeasts.

My next brew will use Verdant yeast so might give it a go on that. I've brewed with Verdant yeast before so familiar with it so hopefully can detect any difference the pressure fermentation will make.

 

[Rodcx500z]

To be honest the reason i do it is so i can do oxygen free transfer which works very well, i don't have temp control yet as space is limited, there are vids on yt on pressure fermenting but i have not watched any

 

[RGeats]

As far as I'm aware esters are formed towards the start of fermentation, so if you just leave the spunding valve set to atmospheric pressure for the first few days you should still get the required flavour. Then close they spunding valve for carbonation. I listen to the outlet of the spunding valve, you can then tell when fermentation is slowing down as the hissing gets quieter. Works for me

 

[RoomWithABrew]

All my ferments are in pressure capable fermenters. If I want esters / yeast expression then I start off with an open ferment either loose lid or airlock. Then when Ispindel shows the ferment is slowing I attach the spunding valve and dial in the pressure I want for the vols. Often this is quite high if the beer is warm.

If I want to suppress yeast expression going for a quick lager or a recipe suggests US05 / wlp001 then I start the spund either straight away for the lager or sooner with the US option. I tend to use opshaug kveik for these ones at about 30 celsius and the pressure reaches about 30 psi.

It's very surprising to me how much pressure can be built up when fermentation appears to be really tailing off. Even 3 or 4 gravity points seems enough to get to about 15 psi plus over a few days.

I've got a beer that the gravity has been stable for several days and around 12.5 psi, turned the heat off and a little while later heard a small leak as the lid wasn't fully tight. Pressure was 10.5 psi at that time.

Now having cooled from 23 to 18 and a few days later the pressure is now 13.5 psi so some background ferment must be going on. It is Hazy Daze II yeast that has a combination of yeasts in and one is STA+ so that might account. But the beer is clearing which normally suggests to me it's also done. Time to cold crash I guess.
It's a beer where I pitched an american pale ale wort onto the dry hops of a hazy DDH ipa, I'd dropped the yeast bulk out before the dry hopping. Samples I got when dropping the yeast out suggest there was plenty of aroma out of the 200 g of original dry hops left. Plenty of yeast expression as well.

A week or so before it's ready to keg though.

 

[foxy]

thanks for that, it's interesting but not sure it answers my specific question about the production of Esters from yeast under pressure. I've done a bit of googling and found some material that suggests the yeast esters are produced int he first 36hrs of fermentation. If that is the case then I can start spunding after 36hrs or so, so as not to suppress yeast esters in beers where it is desirable but yet still achieve carbonation, which sounds like a plan. think I'll give it a whirl and see what I get.

I guess the next challenge will be to determine what pressure and temperature to ferment at so when I cold crash I end up with the desired level of carbonation.

This is the article which started the pressure fermentation off among home brewers. It emulates the process used by commercial brewers in partially carbonating the beer as it finishes. As per usual the method has now been corrupted by the home brewer, one can now read so many different takes on the method that someone new coming into closed vessel fermentation would be confused.
http://www.terifahrendorf.com/Closed-Pressurized-Fermenatation.pdf
Some other reading.
Pressurized Fermentation | Spike Brewing
http://scottjanish.com/fermenting-dry-hopping-pressure/

 

[RoomWithABrew]

The Janish article is very good.

Scaling things down does make a huge difference that homebrewers can't compensate for. But it's all fun. The fact there are so many different approaches suggests that there is no " right way ", there aren't many randomised controlled trials. Even the same beer open fermented in a big conical will come out different to a ferment in a shallow square fermenter. Finding a way that works for you and that makes acceptable beer is the key. Perfection is the enemy of good.

 

[foxy]

The Janish article is very good.

Scaling things down does make a huge difference that homebrewers can't compensate for. But it's all fun. The fact there are so many different approaches suggests that there is no " right way ", there aren't many randomised controlled trials. Even the same beer open fermented in a big conical will come out different to a ferment in a shallow square fermenter. Finding a way that works for you and that makes acceptable beer is the key. Perfection is the enemy of good.

That is all it is. Fun. If folk want to pressure ferment from go to whoa that is up to them. I can understand some beers may benefit from some pressure to reduce esters. Chris White who has a BS and Ph.D in biochemistry also said he wishes someone would invent an open fermenter for home brewers. I have read of people who will pressure ferment stout, porters and ales! There is a lot of misconception of pressure fermenting, some home brewers will do their own research and others won't. Marston's paid for research in pressure fermenting and wisely declined to go down that path.
I prefer Perfection is the enemy of progress. Otherwise we would still be rubbing sticks together to light a fire.

To answer the original post. Yes there is a difference between cask and bottled conditioned ales. Both are superior to forced carbonated ales. And it is the natural carbonation which plays a major part. Though with the cask conditioned ales they have the advantage of nitrogen being introduced during serving through the hand pump.

 

[hoppyscotty]

Thanks all. I'll give it a go. I have pressure fermented before to just see what its all about and all went well though I cant say I noticed a great difference in the end product. I think this is an area that the home brewer can exploit moreso than on the commercial scale as the cost of a pressure rated and capable fermenter on the small scale is far far cheaper and technically easier than a large several hundred or thousand litre vessel...as you scale up the size of the vessel then the weight and complexity of it being pressure capable suddenly becomes a big and expensive challenge. But like everything, you need to have a goal and out to achieve something and that is what I'm struggling with and trying to achieve bottle/cask conditioned quality of carbonation then that is a worthy goal for sure.

 

[dcbrookes]

Consider Champagne v. Prosecco. Champagne is carbonated naturally, Prosecco is force carbonated after fermentation. There is general agreement as to which produces the better wine. If this were not the case, why would winemakers the world over boast that they use the "methode Champenoise"? To me one of the great benefits of pressure fermentation is the natural carbonation (which also, coincidentally saves time).

 

[hoppyscotty]

OK I'm convinced. I have an American Stout/black IPA in the fermenter at the moment and not far off halfway through fermentation at 19 degrees C with a blow off tube. I could add my spending valve later today or early tomorrow. The question is what pressure do I shoot for to achieve the desired level of carbonation in the finished beer?

Assuming I want to achieve a carbonation level of around 2.4 or so volumes in the finished beer at fridge temp (5 degrees C) then if I were force carbonating then according to a carbonation chart that translates to 12 psi.

At 19 degrees fermentation temp the carbonation chart suggests a much higher pressure to achieve 2.4 volumes...actually my chart tops out at 17 degrees C and that correlates to a pressure of a bout 22 psi. That feels a bit high.

Is my logic correct that the same force carbonation chart applies to the temps and pressures in the fermentor at fermentation temperatures?

 

[dcbrookes]

I ferment at 10psi, but I don't cold crash and I don't like my beer too fizzy. Your 12 psi looks about right, or why not start at 15 psi and see how it goes?

 

[RoomWithABrew]

OK I'm convinced. I have an American Stout/black IPA in the fermenter at the moment and not far off halfway through fermentation at 19 degrees C with a blow off tube. I could add my spending valve later today or early tomorrow. The question is what pressure do I shoot for to achieve the desired level of carbonation in the finished beer?

Assuming I want to achieve a carbonation level of around 2.4 or so volumes in the finished beer at fridge temp (5 degrees C) then if I were force carbonating then according to a carbonation chart that translates to 12 psi.

At 19 degrees fermentation temp the carbonation chart suggests a much higher pressure to achieve 2.4 volumes...actually my chart tops out at 17 degrees C and that correlates to a pressure of a bout 22 psi. That feels a bit high.

Is my logic correct that the same force carbonation chart applies to the temps and pressures in the fermentor at fermentation temperatures?

Use this
https://drhansbrewery.com/beercarbonationcalculator/
If you want 2.4 vols at 19C then its 25 psi. .

When you cold crash it CO2 gets absorbed into the stout so the pressure will fall above the beer as well so it will then be around the 12 psi , you don't need to vent CO2 to 12 psi it will fall to that level. If it's a bit higher after cold crash in the fermenter you often lose a psi in the closed transfer.

As mentioned above I start the pressure ferment later than half way with the spunding valve targeting my final vols related to the current ferment temperature. You will see that if you are at 30 celsius the pressures are even higher.

Note If you are going to put your stout on nitro then you need much less CO2 Vols as say 30psi of beer gas 75 nitro and 25 CO2 will be 7.5 psi to spund to then transfer and on the beer gas it will be bang on.