Fermenting Under Pressure

[kadmium]

Oxygen is the main enemy of hop flavour and aroma, so doing a 'zero' oxygen transfer using a closed system is best practice. The easiest way to purge the keg is to fill it full with your sanitiser (starsan) and then transfer it out into either another keg or what not. I have a spare keg on rotation that I use a jumper (black disconnect to black with beer line) so that I can directly push the sanitiser out via the dip tubes. This empties the keg and leaves it full of only CO2. (burp the keg a few times before transfering to purge the headspace)

Then, use the same jumper to move the beer from the pressure fermenter into your now clean, sanitised and emptied keg. One tip, is to do the transfer and purge the keg right before, but fill and pressurise the day before, and then put your spunding valve on it to make sure pressure doesn't drop and you don't have a small leak. I take my spunding valve off when I cold crash, because it's not needed anymore and I found mine would get wet with condensation sometimes.

So, take spunding valve off fermenter, and cold crash. Fill a keg with starsan and burp, then pressurise. Put spunding valve on (should tell you the pressure, and make a note of what pressure it's at). Check the keg the next day to see if you have the same pressure (a keg full of just gas varies too much, so a keg full of starsan and small headspace is more reliable). If pressure is stable, transfer starsan out. If pressure has dropped, check keg for leaks, make sure lid is sealed correctly etc. Better to find out before filling it up, rather than later. Then, transfer beer into keg and enjoy.

Some people capture the CO2 during fermentation, by putting a keg next to fermenter, putting gas out on fermenter to liquid out on the keg, and spunding valve on gas post of keg. The gas flows from fermenter via gas post, into keg via liquid post, then pushes the gas out via the spunding valve on the gas post. If you sanitise the keg, and then capture the CO2 you end up with a fairly well purged keg (free co2) but that's too much effort, and I'd rather spend the 40c on gas to do it the way I do.

 

[Staggerin]

Thanks Kadmium. I will try that out when the next brew has finished.

I have run a couple of K&K brews through the pressure fermenter now, so I dont waste the good stuff working this all out. The first was a lager with the kit yeast, which stalled at 1018, tried raising the temp but nothing really happened. I assumed that the yeast didn't like the pressure? cold crashed , gelatine then kegged it anyway as its a light lager for the wife, and she is not very fussy.

The second brew is another lager kit but I have used S-189, gone mad for the first two days and now slowed right up. running at 15C. Spunding valve set at 5PSI.

Is this normal for a pressure ferment?

 

[kadmium]

Hey mate. Depends on the yeast, sometimes they under attenuate if you don't pitch enough. If you are going to ferment low you probably want to pitch like 3 packs or even 4 for a lager.

To truly take advantage of a pressure fermenter, and the main advantage is to ferment your lagers hot.

I would run 15PSI and 20c from the get go. Should be over and done within a week including diacetyl rest (considering you're fermenting at rest temps)

The advantage of pressure is it inhibits esters as well as off flavours from traditionally fermenting hot. A lager yeast under no pressure at 20c will not be great. But a lager yeast at 20-22c under pressure (15-20PSI) will produce clean, crisp ferments without the sulfur, fusel and other off flavours.

So next time, pitch two packets of lager yeast and let rip in the low 20s under 15PSI and see how it goes.

There are videos and guys online doing 1 week lagers including gelatine fining from grain to glass. A bit quick for me, but I tend to do a week in fermentation, cold crash and gelatine fine then keg. Total is around 10 days to keg. I then let it sit on serving pressure for about 2 weeks in the keg before drinking.

A slight bit of haze and condensation but this is a Czech Pils I did (ran out of whirlfloc on the day doh)

It has since dropped crystal clear *about 4 weeks in the keg *

 

[Nickedoff]

I'm very new to brewing but I've pressure fermented a lager at 15psi and two ales at 5psi, but with the temp at the high end of the recommended temp range for the yeast. Just using one pack of dry yeast for 20l and haven't had any issues. I reckon you could bump up the temp and pressure a bit.

Edit: kadmium beat me to it with a much better answer

 

[Staggerin]

Thanks Guys,

I did actually put two packets of kit yeast in the first one, but it looks like I'm running a bit too cool and too low a pressure from what you are saying. Luckily I can access my fermentation fridge remotely, so i will up the temp now and see how it looks tonight.

I was just worrying about it last night as after 2 days the krausen seemed to be dropping. I will take a proper SG sample tonight and see where it sits.

Thanks again.

 

[kadmium]

Yeah,

realistically the amount of yeast you need to pitch is based on a variety of factors, with fermentation temp, gravity, volume being the key aspects. Things like oxygenation etc come into play for liquid yeast, dry yeast doesn't need it.

The average pitch rate for an Ale is .75m per ml (or 7.5B per litre) and Lager is twice that (if fermenting at lager temps) so 15B for 1/L for a Wort of 1.040 once you go above this the amount scales up, but for a 1.040 and a standard 20L wort should require 150B cells for Ale and 300B for a lager.

For a Lager around 1.055 you would need 200B for an Ale and 400B for a lager. Each dry package contains on average 20B per gram, so for 11g you get around 220B cells. This means a big pack requires a minimum of 2 for a lager. However, some Kit yeasts are only around 5g whereas the big players (Fermentis etc) come in 11.5g packets.

You would need 4x5g packets or 2x11.5g packets to get an adequate pitch for lagers at low temps. The advantage of brewing a Lager under pressure at Ale temps is you don't need as much yeast. So, fermenting under 15PSI at a higher temp means you can pitch it closer to Ale temps, being 1x 11.5g packet.

I would suggest if you intend on doing lagers, a cheap insurance to ensure you don't stall out is to use something like Saflager W-34/70 and pitch one packet into anything up to 1.055 OG and anything over pitch 2 packets if fermenting at 20c under pressure.

Your other option is to invest in making Yeast starters and going down the liquid yeast route (saves money in the long run, but does have an initial startup cost) which would let you play with other strains. For example my Czech Pils uses the Pilsner Urquell strain, although having said that Dry yeast have come a long way in terms of variety.


Also, don't forget you should ferment for around 4 days at low temps, and then raise the temp about 2c a day till you hit 20c then rest for a few days then crash. So ideally you would start around 12c and after about 4 days go 14, 16, 18, 20 then rest for 2 then crash (10 + 1 day to crash then 2 days cold) about 13 days or so. Running it warm, you can just ferment for about 5 days at 20c (until you reach FG and then leave it a day or two at FG to clean up) then crash. I use a TILT and monitor the gravity, once I see it has stabilised for a few days, I then crash it. Most ferments are done under a week, with a cold crash maybe a touch longer. I then fine with gelatin in the fermenter and transfer about 3 days later. I can get most beers out within 2 weeks and if I really wanted to go fast, I could go Kveik and probably ferment in 2 days, crash and fine and keg within a week but i'm not too interested in that.

Don't forget, that pressure will inhibit ALL esters, so particularly pay attention to classic estery beers like some ales, weis beers, heffeweizens etc. You can set your spunding valve to like 1PSI so it virtually acts as an airlock, and after fermentation is basically done you can ramp the pressure to try and catch some free carbonation but I don't usually bother.

 

[Staggerin]

Thanks, Great advice.

 

[BrewLizard]

I'm about to go down the pressure fermenting + closed transfer route after having a few beers that lost hop brightness, and one that turned to stale cardboard in 1 week!

I had already stopped cold crashing in the primary to avoid O2 ingress, and changed to keg hopping instead of fermenter dry hopping to keep hop aromas as fresh as possible.

I'm going to start doing the method @kadmium posted at the top of this page (#741), using a vacuum-sealed, sanitary magnet to drop dry hops into the fermenting beer. My question is: what's the best way to add gelatine to the keg (or FV) when doing closed transfers? I've seen the syringe injection method, but I'm worried about injecting air.

Is there any way to have gelatine in a cup (with a magnet) on the wall of the fermenter and drop it in before cold crashing? Seems it would just turn into a lump of jelly...

 

[kadmium]

The easiest way to gelatine fine I have found is to use a Carbonation T piece! 2 carb caps and some beer line.

Mix up the gelatine in a glass jar using boiling water. Pop lid on and let it cool down to room temp.

Add it into PET bottle that you have purged with CO2. (Put the contraption on the bottle, and loosen the cap to allow co2 to flow through bottle)

Then I bubble co2 through the gelatine to purge it a touch more.

Then push it through the gas post on the fermenter and bobs your aunt.

 

[Nickedoff]

The easiest way to gelatine fine I have found is to use a Carbonation T piece! 2 carb caps and some beer line.

Mix up the gelatine in a glass jar using boiling water. Pop lid on and let it cool down to room temp.

Add it into PET bottle that you have purged with CO2. (Put the contraption on the bottle, and loosen the cap to allow co2 to flow through bottle)

Then I bubble co2 through the gelatine to purge it a touch more.

Then push it through the gas post on the fermenter and bobs your aunt.

Dr Hans has a good YouTube video on how to do this @BrewLizard. I used the liquid post but then ended up with gelatine setting in the dip tube.

 

[BrewLizard]

Thanks guys. I’ll check out the video.

Forgot about carb caps. I have one + a tiny coke bottle that might do the trick.

 

[Nickedoff]

I needed a grand final beer quickly, so I put down a fwk (G&G draught) on Monday night with 2 packs of s-189. Put 25psi on it and ramped up from 18c to 24c. Pretty much fermented out now, tiny bit of krausen left. Just bumped it up to 25c to hopefully clean up so I can start cold crashing in the morning.

Just a bit of fun, let's see how it goes.

 

[kadmium]

That's the great thing about pressure. Quick clean beers are easily had. Let us know how you go!

 

[Nickedoff]

Didn't quite make it, yeast is still cleaning up a bit so I'll leave it for a couple.more days.