Flavor and aroma loss - I can not figure out why this keeps happening!

[Broken Crow]

The way I did it was in reverse - keg sits upright, fill with the lid closed tight but PRV open. Once liquid shoots out the PRV I close it and add a bare disconnect on the gas-out. The liquid then starts to come out the disconnect. While it is coming out I tilt the keg towards the liquid-in post. You will then see the liquid stop coming out for a bit (assuming that is the air pocket). I then take the disconnect off while the liquid is still coming out and it is finished.

Hmmm... OK, got it! I'm still not certain as to which way would leave more air inside.... doesn't the gas dip tube extend below the top of the keg? ...I'm gonna have to open my kegs now and look.

 

[Bassman2003]

Yes it does unless you trim it which is important for liquid purging.

 

[doug293cz]

Thank You!! You are my first-call Authority on here for math and electrical matters. I don't want to sound unapprciative or lazy, but; embarassing as this is, the part of my brain that comprhends and processes both the language and abstractions of numbers, volumes, measures, and 3D cognitive modelling, as well as the size of data-sets I can process was quite literally ripped away in 2014. (I can even trust myself to accurately count to 100 now and I used to be a maths ace )... About what percentage of a 5 or 10 lb CO2 cylinder is consumed using the 'pull the PRV x-many times' method that has been stated above?
..Like I said; this is embarassing because I can see it's just simple math, but despite my best efforts, my brain gets swamped trying to calculate it. (and I'm worried I may just be going on assumptions, but I can't be sure because connections to my insular gyrus are ripped up as well )

Sorry that you have to deal with cognitive challenges.

The amount of CO2 used will depend on the headspace volume. A ball lock corny keg has about 20.1 L total volume. 5 gal is about 19 L, so if you have a full keg the headspace is about 1.1 L. So, the volume to be purged can be anywhere between 1.1 L and 20.1 L.

If purging at 30 psig, each purge cycle uses 30 / 14.7 = 2.04 "volumes" of CO2. 1 volume of CO2 is equivalent to 1.977 g/L, so the total CO2 to purge is:

Purge CO2 (g) = Headspace vol (L) * Number of Purges * 2.04 * 1.977 g/L​

​

13 purges of a "full" keg @ 30 psig would use:

Purge CO2 = 1.1 L * 13 * 2.04 * 1.977 g/L = 57.7 g or 0.127 lb​

​

13 purges of an empty keg @ 30 psig would use:

Purge CO2 = 20.1 L * 13 * 2.04 * 1.977 g/L = 1.05 kg or 2.32lb​

​

That empty keg purge takes almost 1/2 of a 5 lb CO2 cylinder to accomplish. You don't want to use this method on anything but (almost) full kegs.

Brew on

 

[Broken Crow]

Thank You again!!! I don't want to derail this thread, but I'm nearly in tears because you laid it out so simple I can understand it! Math and comparative models used to come natural to me and half the reason I chose homebrewing as a therapy was my previously long-held belief in 'guided neuroplasticity'..that is: do the sort of things you did before the ripped axons in order to regrow, if not the original neural-net, at least re-engage the appropriate gyrii to establish functional new pathways. Even as late as 2 or 3 years ago when it came to something as simple as making coffee and pouring a mug for my girlfriend and one for myself, I'd fill one about 2/3 and the other right up to the rim and I saw them as being 'the same' even though I could plainly see that they were in some way 'different'...I had to study them to try and figure out which one was fuller....and that's without considering the horrible measurements I used in making the coffee (which I had a previous repution for doing Perfectly for 40 years, but...)
Back to the CO2 consumption; Thanks! That's far less than I thought..but still, I'd rather fill all the space with Star San (which itself probably contains dissolved O2)... I'll probably try the full submersion at some point, but now you've given me the peace of mind on a practice I can use in a pinch, and in the meantime I'll try and use the math you provided in concert with letting CO2 in my liquid post to maximize bubbles while purging to get some idea of the remaining O2.

 

[mac_1103]

The amount of CO2 used will depend on the headspace volume. A ball lock corny keg has about 20.1 L total volume. 5 gal is about 19 L, so if you have a full keg the headspace is about 1.1 L. So, the volume to be purged can be anywhere between 1.1 L and 20.1 L.

If purging at 30 psig, each purge cycle uses 30 / 14.7 = 2.04 "volumes" of CO2. 1 volume of CO2 is equivalent to 1.977 g/L, so the total CO2 to purge is:

Purge CO2 (g) = Headspace vol (L) * Number of Purges * 2.04 * 1.977 g/L13 purges of a "full" keg @ 30 psig would use:

Purge CO2 = 1.1 L * 13 * 2.04 * 1.977 g/L = 57.7 g or 0.127 lb13 purges of an empty keg @ 30 psig would use:

Purge CO2 = 20.1 L * 13 * 2.04 * 1.977 g/L = 1.05 kg or 2.32lbThat empty keg purge takes almost 1/2 of a 5 lb CO2 cylinder to accomplish. You don't want to use this method on anything but (almost) full kegs.

This definitely deserves a Ctrl+D!

 

[TLaffey]

That's far less than I thought..but still, I'd rather fill all the space with Star San (which itself probably contains dissolved O2)...

Yes, and also chlorine/chloramine. I add SMB when filling to remove both.

 

[Spivey24]

Yes, and also chlorine/chloramine. I add SMB when filling to remove both.

Why does it contain chlorine? Just because of the water used to make the star San?

 

[An Ankoù]

I use a Brewtools inline filter when kegging.

Why are you filtering a cloudy IPA?
Do you know what you're filtering out?
Quite possibly the hop oils that carry the flavour.

 

[Spivey24]

So what if there is a little O2 left in the purged keg or lines? Does it really matter? Say a small volume of air at 20% O2 diluted by 5 gallons of CO2 puts you in the parts per thousands or ten thousands. Then you go to transfer, and the beer pours into the keg pushing out all of that CO2 and O2. As the beer pours in, the gas mix swirls around in the keg and some O2 molecules hit the surface of the beer that is coming in. How much of that O2 then gets absorbed by the beer in the time it takes to fill? Say 10 minutes or so. In my brain it seems like a very tiny amount.

And further to this point, I know I get O2 in when dryhopping and that O2 will sit there for a week. Yet I take a sample from the fermenter before transferring and it’s amazing. Yet transfer to keg in a closed loop purging everything and it’s gone in a couple of days. Something more has to be going on.

 

[day_trippr]

When I read the above I see accumulating damage with an unsurprising outcome...

Cheers!

 

[Red over White]

With as close to perfect closed xfer from a pressurized fermenter as I can do into a fully fermentation purged keg, I notice a decline. Is it the headspace during the xfer and also the headspace in the keg as it's consumed? I think there may be something to the headspace having an impact, but it is only a theory.

 

[day_trippr]

For a start, always CO2-purge transfer hoses, and avoid pushing fermentor headspace gas into a keg unless the fermentor was never opened post-pitch...

Cheers!

 

[Spivey24]

I am starting to wonder if O2 mixed in with the bottled CO2 is part of the culprit. I wonder if I could test by bottling a beer at time of kegging in a purged and primed bottle and compare.

 

[CascadesBrewer]

Yes, and also chlorine/chloramine. I add SMB when filling to remove both.

How much SMB do you add? I know that The Home Brew Network has a video on his YouTube channel where he purges his kegs with Water + Metabisulfite instead of StarSan. I have been tempted to try that.

 

[TLaffey]

Why does it contain chlorine? Just because of the water used to make the star San?

Yes, I was assuming use of tap water, not RO. If you use municipal tap water for your Starsan solution, there's going to be chlorine/chloramine in there.

 

[TLaffey]

How much SMB do you add? I know that The Home Brew Network has a video on his YouTube channel where he purges his kegs with Water + Metabisulfite instead of StarSan. I have been tempted to try that.

Thanks for that reference; I may want to try that also. This is the thread that got me started on this:
Adding Sodium Metabisulphite to Keg to reduce oxygen.

I currently add 2gm SMB to 6G of starsan, which I believe to be overkill. I push out every little bit of solution before introducing beer. (I have shortened my gas tube and invert the keg to remove the last bit of solution as a final step in purging.)

 

[Bassman2003]

I am starting to wonder if O2 mixed in with the bottled CO2 is part of the culprit. I wonder if I could test by bottling a beer at time of kegging in a purged and primed bottle and compare.

This is a definite problem. The best defense is to use as little bottled CO2 as possible or buy research grade CO2 which is hard to find and probably cost prohibitive. As I posted earlier in the thread - the O2 game is difficult. All we can do it try to find ways to minimize the effects. But the first step is realizing/admitting that these seemingly tiny things throughout the process have a negative impact.

 

[mac_1103]

I am starting to wonder if O2 mixed in with the bottled CO2 is part of the culprit.

There are threads on this topic. For example.

 

[user 338926]

If it were in any way practical, I'd get myself a tank that I could submerge my entire corny in, tall enough that I could turn the lid upside-down and get that last tiny bubble out before clamping the lid down...as it is, I routinely use nearly six gallons of Star San, as I let it run out the top while I submerge as much of the lid as possible and just plain hope the the CO2 filled Star San bubbles I follow it with are enough to get that last bit of air to the PRV.

There is one practical way. It might require two kegs or at least one keg and something else you can pressurize with sanitizer in it and connect it as a sanitizer source.

Make a jumper hose with a gas fitting and if you are using another keg let's say, then you also need a beverage fitting on the other end. Now you need another beverage fitting preferably with a piece of hose on it long enough to get above the top of your keg you're trying to purge. That length is so it doesn't become a siphon or allow air back in.

Fill your keg with sanitizer. Stick the lid on. Now turn it upside down and connect your jumper hose from the liquid out of the source vessel to the gas in on your beer keg. Once you put pressure on the supply vessel, connect the other beverage line to your now upside down beer keg on the beverage fitting. The only air that can remain is what is not Disturbed and sent out by the liquid which is leaving through the beverage dip tube. I would guess that even the tiniest bit of pressure will create enough turbulence around the dip tube to remove the last tablespoon of air that could possibly be in that tank. There you go now fill it with CO2.

 

[OzzyPeeps]

If it were in any way practical, I'd get myself a tank that I could submerge my entire corny in, tall enough that I could turn the lid upside-down and get that last tiny bubble out before clamping the lid down...as it is, I routinely use nearly six gallons of Star San, as I let it run out the top while I submerge as much of the lid as possible and just plain hope the the CO2 filled Star San bubbles I follow it with are enough to get that last bit of air to the PRV.

But starsan has dissolved O2 in it and there's always a bit left in the keg ... how many people who use this method aren't bothering to dose their starsan with SMB

Better yet use saniclean to eliminate foaming residue l

I am not sure how long your cycles are and how much CO2 gets moved per cycle. But the overall point is that a sanitizer purge with CO2 or a fermentation purge are the best options. It is kind of a quest to get the dogma of pulling the PRV out of the homebrew world. It is just not the best approach and it was taught as the only approach for a long time...

Clearly the best method is a combination of best processes - i.e. sulphited liquid purge with fermentation gas.


There is one scenario I've been thinking of that would benefit from a 30x 30psi vent purge:

O2 free dry hopping in keg:

1)Fill keg with sulphited sanitizer up to about 85% full.

2)Using neodymium magnets, ss nuts and a nylon mesh, suspend the open mesh like a trampoline above the liquid and add(Frozen) hop charge so it's suspended above liquid by mesh

3) pop lid on and purge the 1 quart/ 1 liter headspace 33x at 40psi.

4) purge the rest of the liquid with ferm gas.

5) push some beer (or deoxygenated water) down the liquid out tube and then back up the same tube to clean out residuals Sani like @Red over White does

6) remove magnets to drop hops and closed loop transfer from fermenter to rack onto hops

7) pressurise to seal

8) lie keg on side on floor and kick/roll it around for 4 or 5 days at room temp

9) serve

Tasty!

 

[mac_1103]

It's been shown that purging an empty keg with fermentation gas is essentially 100% effective. So if you purge a starsan-filled keg instead then any oxygen that was dissolved in the starsan will also get removed unless you disconnect the keg as soon as the liquid has been pushed out.

 

[OzzyPeeps]

Interesting ... I suppose the o2 reaches equilibrium with all the co2 above it and sublimes

 

[mac_1103]

I would expect the oxygen in the starsan to come out of solution as the partial pressure of oxygen in the headspace drops. So like I said, if you watch the starsan get pushed out and disconnect the keg as soon as it starts pushing gas instead of liquid, then I think there will still be some amount of oxygen in the keg. But if you leave the keg hooked up until fermentation is complete that oxygen gets progressively diluted with fermentation gas until it's essentially gone. I think it may actually be more effective to purge an empty keg with the fermentation gas going in through the liquid post and dip tube, but I'm not the expert on this. @doug293cz is.

 

[doug293cz]

I would expect the oxygen in the starsan to come out of solution as the partial pressure of oxygen in the headspace drops. So like I said, if you watch the starsan get pushed out and disconnect the keg as soon as it starts pushing gas instead of liquid, then I think there will still be some amount of oxygen in the keg. But if you leave the keg hooked up until fermentation is complete that oxygen gets progressively diluted with fermentation gas until it's essentially gone. I think it may actually be more effective to purge an empty keg with the fermentation gas going in through the liquid post and dip tube, but I'm not the expert on this. @doug293cz is.

Pretty good reply. Starting with an empty keg and letting the purge go the entire length of the fermentation, you end up with less than 5 ppb (yes parts per Billion) O2 in the purged keg. Starting with a liquid filled keg would end up slightly lower, but you wouldn't be able to measure the difference.

Brew on

 

[BongoYodeler]

When I'm fermenting oxygen sensitive beers I purge the receiving keg with fermentation through the liquid post and dip tube. But even before brew day, starting with a cleaned and starsan sanitized keg, I hit the keg with a single shot of 30-35 psi CO2 from the tank. I pull the prv to evacuate, thinking I'm still left with at least some CO2 that wouldn't normally be in there, hopefully giving me a little better starting point when I hook it up to capture CO2 once fermentation kicks in. Good idea or waste of time and CO2?

 

[day_trippr]

Regardless, it can't hurt, but still I would vote "waste of time and CO2" - but only because I don't do that, and still have kegs of neipas - perhaps the most O2 sensitive style ever - that are still tasty after 6 months...

Cheers!

 

[OzzyPeeps]

The benefit I see with using liquid in the idea I posted above (attempting to dry hop in a purged keg) is that it would take significantly less time vs just with ferm gas.

The way I see it, the longer hops are sitting there with gas blowing through them the more aroma you are losing.

There's a reason they are vacuum packed in mylar under nitrogen immediately after harvest/processing.

My understanding was that ferm gas from an entire fermentation was 100% effective for a purge ... but that's at least 7 days of blowing gas ... so for the specific application above that I want to try partial liquid would be better.

Also the perfectionist in me is looking at efficiency:

A s I understand it a fermentation produces roughly 40x the volume of the fermentor in CO2.

So with a liquid purge 1 fermentation could theoretically purge AND sanitize 40 kegs

So that's 80 birds with one stone by my math ...

You gotta sanitize anyway, nice to get it out the way

 

[OzzyPeeps]

When I'm fermenting oxygen sensitive beers I purge the receiving keg with fermentation through the liquid post and dip tube. But even before brew day, starting with a cleaned and starsan sanitized keg, I hit the keg with a single shot of 30-35 psi CO2 from the tank. I pull the prv to evacuate, thinking I'm still left with at least some CO2 that wouldn't normally be in there, hopefully giving me a little better starting point when I hook it up to capture CO2 once fermentation kicks in. Good idea or waste of time and CO2?

I'm no expert but I think the accepted wisdom is a full fermentation purge is 100% effective and even food grade tank CO2 has a bit of O2 in it so could be counter productive ... but how the hell you could know for sure I have no idea

 

[OzzyPeeps]

Not to derail the thread too much ... but for those who purge with fermgas using basic buckets or carboys as opposed to fancy pressure fermenters, does anyone use an airtight blow off jar as a sort of quarantine area as insurance against over active fermentations?

I know from a brulosophy article you can purge a keg with a basic ***** bucket or carboy ... but I use a lot of omegas lutra kveik at highish temps and she gets pukey so I don't need that in a keg I'm trying to purge but I'm unsure how to design a blow off jar I know will be airtight

 

[mac_1103]

The benefit I see with using liquid in the idea I posted above (attempting to dry hop in a purged keg) is that it would take significantly less time vs just with ferm gas.

And the benefit of taking the extra time is that you remove more oxygen. You're not going to dry hop until fermentation is done or nearly done anyway, so I don't see much of an efficiency gain. I can't really comment on whether gas moving through the keg harms the hops, but I suppose someone could set up a direct comparison.

for those who purge with fermgas using basic buckets or carboys as opposed to fancy pressure fermenters, does anyone use an airtight blow off jar as a sort of quarantine area as insurance against over active fermentations?

Yes. Krausen catcher. You can buy an overpriced one or DIY it.

 

[hottpeper13]

Ozzy google "thumper for distilling.

 

[Bassman2003]

The dry hopping question is a good one. If you put the hops in the serving keg and kept them suspended until transfer, unless you purged it beforehand, the start of fermentation would have oxygen in the keg. It would take some time to fill with CO2 and remove the oxygen. So in theory, the hops would be in an oxygen environment for some amount of time.

If you are only going to fill the keg up 80% and push out with CO2, then it seems to me you are only lessening the problem (which is not bad). But, it seems like a PITA if you filling and emptying while trying to keep the hops dry... You might be better off daisy chaining two kegs together in the previous brew/fermentation and then starting with one for the next hoppy beer. That way it is purged and dry when you quickly open it and put your magnet bag in before the current fermentation purge begins.

My goal with all of this stuff is to eliminate the use of tank gas outside of serving.

 

[doug293cz]

A s I understand it a fermentation produces roughly 40x the volume of the fermentor in CO2.

So with a liquid purge 1 fermentation could theoretically purge AND sanitize 40 kegs

So that's 80 birds with one stone by my math ...

Why would you need way more purged empty kegs than you have beer to fill them?

Brew on

 

[BongoYodeler]

Not to derail the thread too much ... but for those who purge with fermgas using basic buckets or carboys as opposed to fancy pressure fermenters, does anyone use an airtight blow off jar as a sort of quarantine area as insurance against over active fermentations?

I know from a brulosophy article you can purge a keg with a basic ***** bucket or carboy ... but I use a lot of omegas lutra kveik at highish temps and she gets pukey so I don't need that in a keg I'm trying to purge but I'm unsure how to design a blow off jar I know will be airtight

I bought one of these and a mason jar with starsan to put between my fermenter and keg.

 

[OzzyPeeps]

The dry hopping question is a good one. If you put the hops in the serving keg and kept them suspended until transfer, unless you purged it beforehand, the start of fermentation would have oxygen in the keg. It would take some time to fill with CO2 and remove the oxygen. So in theory, the hops would be in an oxygen environment for some amount of time.

If you are only going to fill the keg up 80% and push out with CO2, then it seems to me you are only lessening the problem (which is not bad). But, it seems like a PITA if you filling and emptying while trying to keep the hops dry... You might be better off daisy chaining two kegs together in the previous brew/fermentation and then starting with one for the next hoppy beer. That way it is purged and dry when you quickly open it and put your magnet bag in before the current fermentation purge begins.

My goal with all of this stuff is to eliminate the use of tank gas outside of serving.

Totally

The idea is to purge minimum headspace of approx 1 quart to hold the charge IMMEDIATELY.

I read a very convincing argument with a lot of math that said 16x would get rid of it all but whatever, do 30x in less than 60 sec.

Now we have hops which are as fresh as they possibly can be (they are still frozen so zero terpenes have boiled off hopefully) inside a keg with as close to zero oxygen as possible (the sanitizer has been doses with SMB)

Ready to rack onto as soon as it's purged...

Thats where the speed of purging liquid vs a purge gas purge comes in, theoretically ...

The thread is about retaining elusive aroma. Stands to reason that the less time the terpenoids in the hops are boiling off into the gas the more aroma is retained for the beer

How much of a difference that makes in practice comes down to a lot of variables like hop strain, and individual sensitivity of the brewer, but the science behind terpenes boiling points is pretty well established.

When you open a bag of hops, if you can smell them those terps are gone by definition

only thing that could be optimised more would be to speed up the purge with bottle gas but then the trade off is with the unknowable ppms of o2 in your bottle gas ... which gets me thinking...

What is the wisdom on when to hook up the co2 from the FV so there is defi zero o2 left in the headspace? High krausen?

Can someone explain how to multiquote on here I can't figure it out cheers

 

[mac_1103]

Can someone explain how to multiquote on here I can't figure it out cheers

Just select the things you want to quote one at a time and click on "+Quote" in the drop down for each one. Then when you click on "Insert quotes" you will see a list of the quotes you selected. When you click "Quote messages..." at the bottom of that list they'll be inserted in the order shown.

 

[mac_1103]

When you open a bag of hops, if you can smell them those terps are gone by definition

So IOW, minimizing loss of hop aroma and minimizing oxygen exposure are competing goals and unless you've got something fancier than a keg and a mesh bag you're going to have to trade some of one for some of the other. ISTM that minimizing oxygen is more important by far and you should just use more hops to compensate for the inevitable loss of some terpenoids. But I guess that can get pricey so YMMV.

 

[Bassman2003]

If you are just purging the keg and not protecting anything, one can hook it up from the start because it will all blow through in the end. If you are protecting hops, then you could be strategic and hook it up later in to the fermentation.

Another approach some do is to have two kegs attached to the FV. After some time through the fermentation, open the 2nd keg and throw your hops in. This creates and mildly purged environment to start and continues to purge going forward. When it is time to transfer, run the beer in to the keg that has the hops. Let sit for your dry hopping period, then run that beer out in to the other totally purged keg. This gives you a serving keg without any hops and also minimizes the hop contact time with beer and O2. If the hop keg was not totally purged, it would only have contact for x amount of days before the beer is moved on to a totally purged keg. Not too difficult and sort of makes the best out of the situation.

 

[BongoYodeler]

How about something like this and this?

 

[mac_1103]

How about something like this and this?

Yeah, I'd say that qualifies as something fancier.