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Fermenting Under Pressure

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Mya

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@weal - Somewhere in either this monster thread or elsewhere you mentioned about the collection of CO2 for re-use. Is there a separate thread around that that you could point me to?

Or is there benefit in such a thread being created if there isn't already for those new to the game (aka me) who may want to look at taking advantage of this.
Some people use mylar balloons attached to the fermenter to collect CO2 so that when you cold crash it sucks in the CO2 from the balloon rather than just air.
 

jollster101

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Some people use mylar balloons attached to the fermenter to collect CO2 so that when you cold crash it sucks in the CO2 from the balloon rather than just air.
Thanks.

I recall (I think) that WEAL was collecting into a spare keg he had via some method or other. Bit sketchy on the memory hence the ask.
 
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@weal - Somewhere in either this monster thread or elsewhere you mentioned about the collection of CO2 for re-use. Is there a separate thread around that that you could point me to?

Or is there benefit in such a thread being created if there isn't already for those new to the game (aka me) who may want to look at taking advantage of this.
It is somewhere in this thread, as it isn't really anything to do with pressure fermenting I suppose a new thread could be created.
 

MHB

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I know some brewers are very money conscious (tight as a fishes....) but before you go rushing off and storing CO2 that you cant be sure is either pure or sterile.
Every Mole of a gas occupies about 22.4L at STP (0.0oC & 1Bar), the number of moles can be found by dividing a mass by the Molecular Weight (MW) of the gas, for CO2 it about 44MU. I pay $10 a kg for CO2, so for that I get -
1000g/44= 22.73Moles*22.4L/M=509L or enough to fill 25 of 20L kegs or 40cents per keg full.
Lets just say at that price I would happily part with up to $1, just to be sure the gas I use ids both pure and sterile.
I certainly would be investing a lot of time or effort in capturing CO2, or methane from farts either. Both strike me as a pretty problematic.
Mark
 

HaveFun

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Hi,

I'm fermenting under pressure in my corny kegs. And I serve out of them.

I brew mostly Bavarian wheat beer, they don't have to be crystal clear :)

The advantage for me is that I only have to clean the keg.

I adjusted the pressure to around 15psi. But the last time I forgot to adjust the pressure. And I ended up with a fully carbonated brew.

What's the disadvantage if I don't adjust the pressure? The yeast seems fine with it.

Cheers and happy brewing
Stefan
 

theSeekerr

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I adjusted the pressure to around 15psi. But the last time I forgot to adjust the pressure. And I ended up with a fully carbonated brew.

What's the disadvantage if I don't adjust the pressure? The yeast seems fine with it.
Some yeasts don't like it. There's no question that that much pressure is a stressor.

You can mostly get the best of both worlds by adjusting the pressure to your typical range (10-15 psi or whatever you use) for most of the ferment, then adjusting your PRV to ~30-35 psi for the last 4 points or so. That's enough to fully carbonate but minimises the amount of work the yeast do under stress.

But if your favourite yeast doesn't seem to care, do whatever!
 

minikeg1971

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I'm fermenting under pressure in my corny kegs. And I serve out of them.
This is a great idea. I want to do this too. But I wonder how long can the beer sit on the cake/trub for? I guess not an issue if the keg empties in a month?
 

Nickedoff

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This thread is absolute gold. I'm 18 pages in so far, and kicked off my first beer a couple of days ago in the fermenter king. Started easy with a FWK, in a temp controlled fridge with heatbelt and inkbird + Spundit valve - fermenting at 15psi @ 14.5 deg. Seems to be going well so far, was going gangbusters for the first day or two but has settled down a bit now.

Quick question about cold-crashing - if I cold crash from 15PSI after fermentation is finished, is the fermenter going to cave in? Do I need to run a couple of psi into the fermenter to keep the keep the pressure steady while crashing?
 

kadmium

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Hi,

I'm fermenting under pressure in my corny kegs. And I serve out of them.

I brew mostly Bavarian wheat beer, they don't have to be crystal clear :)

The advantage for me is that I only have to clean the keg.

I adjusted the pressure to around 15psi. But the last time I forgot to adjust the pressure. And I ended up with a fully carbonated brew.

What's the disadvantage if I don't adjust the pressure? The yeast seems fine with it.

Cheers and happy brewing
Stefan
Rather than saying yeast don't like it (non descript) increasing pressure is related to a decrease in phenolic and esters. So if brewing a particularly estery beer like a wheat, it can be more subdued.

People carry on about pressure fermenting being bad, but it's really not. It depends what you want to get out of it.

I would personally stick to less than 10psi for a wheat and in the last day or two, crank pressure to carbonate. This will allow esters to be produced and then capture the final part of the ferment for carbonating.
 

razz

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This thread is absolute gold. I'm 18 pages in so far, and kicked off my first beer a couple of days ago in the fermenter king. Started easy with a FWK, in a temp controlled fridge with heatbelt and inkbird + Spundit valve - fermenting at 15psi @ 14.5 deg. Seems to be going well so far, was going gangbusters for the first day or two but has settled down a bit now.

Quick question about cold-crashing - if I cold crash from 15PSI after fermentation is finished, is the fermenter going to cave in? Do I need to run a couple of psi into the fermenter to keep the keep the pressure steady while crashing?
You will need to keep an eye on the pressure gauge Nickedoff. It's my experience that when chilling from 14 degrees down to 4 degrees there is a drop in pressure but usually only about 3-4 psi. You should still end up with 9-10 psi for kegging. You can use pressure tables to work out the drop but in reality it's not much.
 

kadmium

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I just remove the spunding valve. Not much I can do if it's gonna drop pressure, but yeah generally in general its around a 4psi drop
 

Paddy

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What Razz said, I have a tilt and adjust the blow tie to allow the pressure to creep up as the SG starts to steady and loosely aim for 12psi after cold crash, this allows me to pressure transfer fining solution via the gas post as well
 

Nickedoff

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I've been cold crashing for 2 days. Down from 16 deg to 0.5, no issues with vacuum, still at ~12psi.

Once cold crashing is finished, if I want to keep the beer in the fermenter for a bit, should I depressurise, remove the collection bottle with the trub and then re-pressurise?

I've taken a few sample along the way and it's very bloody nice (consequences lager fwk).
 

razz

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I've been cold crashing for 2 days. Down from 16 deg to 0.5, no issues with vacuum, still at ~12psi.

Once cold crashing is finished, if I want to keep the beer in the fermenter for a bit, should I depressurise, remove the collection bottle with the trub and then re-pressurise?

I've taken a few sample along the way and it's very bloody nice (consequences lager fwk).
How long is "a bit" Nickedoff? More than a couple of weeks I would remove the yeast/trub for sure. You can read about yeast autolysis and it's effects on stored beer, but basically, get the beer off the yeast and keep it cold (as you are doing)
 

Nickedoff

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Probably a couple more weeks depending how long it takes my keg to arrive. Just want to make sure I've got the procedure right in terms of depressurisation and repressurisation
 

Staggerin

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Been having some random thoughts about fermenting under pressure...

When you use an air lock with no pressure, people complain about losing hop aromas etc through the airlock, so certain compounds must be escaping.

So, if you are fermenting under pressure (say 5 PSI) are you capturing those compounds and keeping them in the beer? Also, If you are capturing the co2 towards the end of fermentation to carb the beer(say 10 PSI) are you also capturing any nasties that would normally blow off?

Maybe barking up the wrong tree here.

Any thoughts?
 
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If you are looking for retaining the hop aroma this may be of interest.
Hop additions have been pushed back later and later in the brewing process of hoppy beers as brewers look to maximize aroma and flavor. We asked three pro brewers renowned for their hoppy beers how they get the most out of their hops.

Ben Edmunds, Brewmaster at Breakside Brewery in Portland, Oregon

We build on hop flavor through traditional late kettle and whirlpool additions. Even though a lot of the aroma from these charges gets evolved out of wort/beer later on, the residual compounds are important for structure and depth of flavor. Flavors contributed from dry hopping build upon that and provide the majority of the primary flavors in our beers. Judicious use of CO2 hop extract during the boil, mash hopping, dry hopping with whole cone hops, and dry hopping at cooler temperatures all are some more advanced techniques that we’ve used occasionally over the years to drive hop flavor and mouthfeel in certain beers. That said, a traditional hotside schedule with additions at 60 and 10–15 minutes before flameout as well as a whirlpool or 0-minute addition will set you up for a very nice, flavorful, hoppy beer. I also encourage people to use lower alpha hops for late kettle additions — hops in the 6–10% AA range such as Cascade, Amarillo®, and Comet.

We don’t do it for all of our beers, but cooling the wort a bit before adding the whirlpool hops is a technique that allows us to make larger charges of higher-alpha hops in our whirlpool without the concomitant bitterness that a near-boiling addition would bring. I don’t think this has a huge influence on aroma but it allows us to layer soft and rich hop flavors into beers.

On the subject of aroma, the two most important things anyone can do to make a beer with great hop aroma are dry hop it appropriately and keep oxygen out of the beer. Even a small (>10 ppb) pickup of oxygen at the time of packaging will have immediate deleterious effects on aroma no matter how heavily dry hopped a beer is.

We vary dry hop additions based on the type of beer and total dry hop load. Our most basic approach would be a standard 2–3 lbs. per barrel (1–1.5 oz./gallon or 8.5–11.5 g/L) dry hop done around 68 °F (20 °C) after a beer is at terminal gravity, typically 5–6 days after brewing. For hazy IPAs and beers with larger dry hop loads (1.5+ oz./gal. or 11.5+ g/L), we usually split the dry hop into two separate charges. Typically, we do 5–6 days of total contact time.

We’ve seen dry hops as little as 1⁄3 lb. per bbl (0.2 oz./gal. or 1.3 g/L) in a lager have a huge impact on beer aroma, and more is not always more. While a very large dry hop might have some huge short-term aroma impact, it also puts a lot of additional variability into a beer. The hugely dry hopped beer inevitably is going to change more over a 10-, 20-, 30-day period than a beer with a smaller dry hop. That said, our typical dry hop rate for IPAs and other assertive hoppy beers ranges from 2 lbs. per barrel on a mellower pale ale to 5.5 lbs. per barrel (1–2.8 oz./ gal. or 8.5–20.8 g/L) for some double IPAs. Above that, we have not seen much increased impact.

The paradigm in American hoppy beers has shifted to focus primarily on the flavors and aromas driven by Citra®, Simcoe®, and Mosaic®: Tropical fruit, sweet pine, grapefruit, dank, resin, blueberry, mandarin, lavender. The challenge is getting that flavor profile without just using the same three hops over and over. A lot of the New Zealand varieties play well in this realm especially when used as supplemental hops; good Chinook has a lot of overlap with Simcoe® and a lot less mercaptan-derived cattiness; Strata® is the new hop on the block that will join the cool kids club; El Dorado®, Cashmere®, and Comet are all great supporting hops that can be used to great contemporary effect as well.

Ryan Speyrer, Head Brewer at Parish Brewing Co. in Broussard, Louisiana

At Parish we focus on making flavorful base wort with generous late-hopping additions in the kettle. Many of our beers don’t receive hops until flameout at the earliest, and these additions typically range from 1.25–2 lbs./bbl (0.65–1 oz./gal. or 4.8–8.5 g/L) depending on the recipe. We also perform “sub-iso” additions on some beers (including all of our hazy IPAs), where we cool the wort going into the whirlpool tank to below isomerization temperature and add hops at a similar rate. This technique seems to impart richer citrus and melon flavors from hops that already exhibit those potential flavors.

Most of our hop load goes into the dry hop post-fermentation where we will use quantities from 2 up to 10 lbs./bbl (1–5 oz./gal. or 8.5–42 g/L) in a couple of hop bombs we have made in the past. Moving beyond this threshold we have found a significant rise in vegetal, grassy, and hop astringency imparted to the beer (not to mention tremendous yield losses). The later you add the hops in the brewhouse, the more aromatics will be retained in the wort. Generous flameout additions and cooling the wort in the whirlpool before adding even more hops all contribute to aroma. There is no getting around dry hopping to get maximum hop aroma in your beer, however. The active fermentation off-gassing by the yeast will have a scrubbing effect on some of those more volatile hop aroma compounds, so some loss will be observed between the brewhouse and post-fermentation. Conversely, yeast contact with the hops can provide interesting flavor changes via biotransformation whereby certain yeast strains can chemically alter hop aroma oils into new compounds with different flavor profiles.

We add dry hops as soon as primary fermentation is complete and we have pitched any yeast that needs to come from the tank for other batches. We cold crash the tank after removing the yeast and start dumping trub from the bottom of the tank before transfer. Keeping contact with the hops warm will impart undesirable grassy and vegetal notes to the beer, especially with very heavily dry-hopped beers, so we consider the cold crashing step to be more important than simply looking at contact time. We’ve found two days is all that’s needed for most of the flavor to come from dry hop additions.

Jeremy Wirtes, Co-Founder/Director of Brewing Operations at Triple Crossing Brewing Co. in Richmond, Virginia

For us, we place heavy emphasis on dry hopping, and more specifically, hop aroma/quality out of the bag prior to dry hopping. If it smells great out of the bag, chances are it’ll show up in the beer. We dry hop most beers twice with two separate additions days apart to ensure we get the aroma we’re after. We’ll hit the beer with its first round just prior to the tail end of fermentation, and then another round roughly 3–4 days later to get both ends of the dry hop spectrum. We use 3–4 days contact time, which also seems to allow for any hop creep to occur if it’s going to, which with our house UK ale yeast, we don’t often see. Surprisingly enough, with the cleaner Chico yeast we use for our West Coast IPAs and pale ales, we occasionally find hop creep that will throw low levels of diacetyl, which requires some waiting for the yeast to clean up after themselves prior to cold crashing the tank.

We look for both complementary hop character (Amarillo® and Simcoe® are pretty classic in that regard), but we also really like looking for opposing hop character as well, as in Citra® and Columbus, or Mosaic® and Falconer’s Flight®. We just started hop selection last year and that has been an entirely new learning experience for us.

We haven’t yet explored anything north of 6 lbs./barrel (3.2 oz. /gal. or 23 g/L) in dry hop additions, but that doesn’t mean we won’t. One of the greatest things about homebrewing is that you can do ridiculous money wasting things and even if it doesn’t turn out, it’s not your rent or mortgage payment. We have a 7-barrel system we use as a proving/testing ground for many different beers, and we dump a fair amount of them that don’t work out because our 20-barrel production site helps to keep the lights on. Maintaining the freedom to take a chance or trial out something in brewing both commercially and at home is key, in my opinion.
 

kadmium

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I think the notion that you "capture" the aroma of the hops under pressure is nonsense, personally. If you think about it, you only build up to a certain pressure (say 10PSI) and then it gasses off anyway, so those aromas just leave via the spunding valve.

Secondly, you don't fill your keg with the gas in the fermenter, only the liquid, so even if that aroma WAS 'captured' in the fermenter, it wouldn't be making it into your keg or bottles.

Also, capturing the co2 at the end to carb doesn't trap any nasties, as there shouldn't be anything nasty in the beer unless you have an infection. The only thing getting 'blown off' is co2 and maybe some aroma compounds (as discussed above). Things like Diacetyl are in the beer itself, and are metabolised by the yeast, and so don't need to 'blow off' - The only other thing, sulfur (rotten egg smell, typical to some lager strains) will go away in the bottle through lagering, so again doesn't need to have an airlock with no resistance.

If anything, fermenting under pressure suppresses the esters created by the yeast, so you will end up with less yeast aromas (like Banana from heffeweizen) so it actually has some negatives when you ferment under pressure.

I pressure ferment, but that's because I am running hot and I am brewing beers with a cleaner yeast profile. If I was doing a heffe or ale that I want the yeast to shine, I would set the PSI on the spunder to like 1PSI to encourage the esters.
 

Staggerin

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Thanks for your replies. I m just doing my first pressure fermented lager and its bringing up these questions. I was thinking about the sulphur smell, that seems to dissipate with age. So I was wondering if you are not letting this blow off that it may dissolve back into the beer and give an off flavour. But I as you say that disappears with time anyway, which it has done when Ive bottled.

On the hop aroma question, if you pressure transferred to a purged keg, would that help to retain the hop aroma?
 

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