Failing to force carbonate kombucha in minikeg

[gpeled]

First time here trying to force-carbonate my Kombucha in a minikeg (grolwer-werks 1 gallon). It comes with a 16gr co2 cartridge which they say should be enough to force carbonated the 1Gallon at 12 psi, in 2-3 days, and last through serving it. I followed the instruction, left it at 12 psi in the fridge for 2 days, was completely flat. Turned up to 15psi, and bene tasting every day, but now at day 6, still flat. The gage still shows 15 psi, and pushes the liquid out when I open the faucet, so it doesn't seem there's a leak.
Any idea what I might be doing wrong?

 

[eliastheodosis]

First time here trying to force-carbonate my Kombucha in a minikeg (grolwer-werks 1 gallon). It comes with a 16gr co2 cartridge which they say should be enough to force carbonated the 1Gallon at 12 psi, in 2-3 days, and last through serving it. I followed the instruction, left it at 12 psi in the fridge for 2 days, was completely flat. Turned up to 15psi, and bene tasting every day, but now at day 6, still flat. The gage still shows 15 psi, and pushes the liquid out when I open the faucet, so it doesn't seem there's a leak.
Any idea what I might be doing wrong?

Not familiar with this setup at all so I have no idea if this is a good question, but...any chance there's a valve downstream of that gauge? Maybe your gas is getting to that gauge but is cut off somewhere downstream before going into your keg.

Never mind, I see you say it's pushing the beer out. Is it possible you have a leak somewhere with the keg? You might be able to muster enough pressure to push out the liquid but when it's sitting it can't build up pressure enough to force the CO2 back in the beer without it leaking out. If you run out of gas I would definitely bet that's the problem There are a bunch of resources on checking for leaks with kegs so maybe check that and give your keg a physical inspection to see if you can find and fix any issues.

 

[mac_1103]

It comes with a 16gr co2 cartridge which they say should be enough to force carbonated the 1Gallon at 12 psi, in 2-3 days, and last through serving it.

That doesn't seem right. "Set and forget" force carbonation generally takes weeks not days.

 

[eliastheodosis]

Yeah, can you post the type of setup this is and the directions they gave? I would be curious to read that and it could be helpful for us to give feedback.

 

[mac_1103]

I think 16 grams of CO2 is about 2.3 gallons. Or enough to carbonate one gallon of beer to 2.3 volumes if the entire contents of the cartridge are injected into the keg and given sufficient time to be absorbed by the beer. So I would expect to need more than one cartridge to carbonate and serve no matter what the directions say. I've never used one of these growlers, but my experience with 1.6 gallon minikegs suggests that you're much better off not trying to force carb with 8 or 16 gram cartridges. I don't know if there's any way to connect a larger CO2 supply to a uKeg.

 

[gpeled]

Yeah, can you post the type of setup this is and the directions they gave? I would be curious to read that and it could be helpful for us to give feedback.

Sure, here is their page with an instructional video and some tips
https://www.growlerwerks.com/blogs/...gh pressure,beverage will be fully carbonated

 

[doug293cz]

You don't have a leak. If you did, your CO2 would all be gone (gauge pressure down ~0) after 6 days.

Couple of questions:

1. Did you refrigerate the keg?
2. Did you purge the headspace of air, and if so, what was your process?

It takes more pressure to carbonate to a given level at room temp vs. cold. There are some fairly simple formulas, as well as tables and on-line calculators, that will tell you how much carbonation you will get at equilibrium for any combination of pressure and temperature. If you didn't refrigerate, your carbonation level will be lower than expected.

The gauge pressure needed to achieve any given carbonation level assumes that the headspace is 100% CO2. If you don't purge the headspace of air, then the actual CO2 pressure (rigorously the partial pressure) will only be about 1/2 of what is required for a gauge pressure of 15 psi. So, not purging the headspace of air will result in lower carbonation than expected.

The video linked recommends three purge cycles, which will remove ~88% of the air if purging at 15 psi. This is adequate to get reasonably close to the expected carbonation level, but not enough to protect the beverage from oxidation, if that is a concern (I don't know how important that is for kombucha.)

Carbonating to 1 "volume" of carbonation requires about 2 g of CO2 per liter of beverage, so 1 gal requires about 7.6 g of CO2 to get 1 volume. Typical carbonation levels for beer are about 2.5 volumes, so carbonating to that level requires about 19 g of CO2. Pushing 1 gal of beer at 15 psi will require about another 2 volumes, or about 15 g of CO2.

Now, you may have some residual CO2 in the kombucha from fermentation, but the actual level will depend on whether the fermentation was open or closed (i.e. with an airlock.) If open the residual CO2 will be close to 0, but if closed should be around 0.8 - 0.9 volumes, which will reduce the amount of CO2 required to carbonate to the desired level.

A 16 g cartridge is about enough to carbonate and push 1/2 gal of beverage, but 1 gal will require 2 cartridges.

Brew on

 

[gpeled]

You don't have a leak. If you did, your CO2 would all be gone (gauge pressure down ~0) after 6 days.

Couple of questions:

1. Did you refrigerate the keg?
2. Did you purge the headspace of air, and if so, what was your process?

It takes more pressure to carbonate to a given level at room temp vs. cold. There are some fairly simple formulas, as well as tables and on-line calculators, that will tell you how much carbonation you will get at equilibrium for any combination of pressure and temperature. If you didn't refrigerate, your carbonation level will be lower than expected.

The gauge pressure needed to achieve any given carbonation level assumes that the headspace is 100% CO2. If you don't purge the headspace of air, then the actual CO2 pressure (rigorously the partial pressure) will only be about 1/2 of what is required for a gauge pressure of 15 psi. So, not purging the headspace of air will result in lower carbonation than expected.

The video linked recommends three purge cycles, which will remove ~88% of the air if purging at 15 psi. This is adequate to get reasonably close to the expected carbonation level, but not enough to protect the beverage from oxidation, if that is a concern (I don't know how important that is for kombucha.)

Carbonating to 1 "volume" of carbonation requires about 2 g of CO2 per liter of beverage, so 1 gal requires about 7.6 g of CO2 to get 1 volume. Typical carbonation levels for beer are about 2.5 volumes, so carbonating to that level requires about 19 g of CO2. Pushing 1 gal of beer at 15 psi will require about another 2 volumes, or about 15 g of CO2.

Now, you may have some residual CO2 in the kombucha from fermentation, but the actual level will depend on whether the fermentation was open or closed (i.e. with an airlock.) If open the residual CO2 will be close to 0, but if closed should be around 0.8 - 0.9 volumes, which will reduce the amount of CO2 required to carbonate to the desired level.

A 16 g cartridge is about enough to carbonate and push 1/2 gal of beverage, but 1 gal will require 2 cartridges.

Brew on

1 - I first refridgerated the kombucha so that when poured into the minikeg, it was already cold. Then it sat in the fridge the whole time, other than when taking out for tasting.
2 - I did not do anything to purge the headspace. Didn't see any mention in if that in the video or the written instructions. Where are you seeing the 3 purge cycles?
Thanks!

 

[gpeled]

1 - I first refridgerated the kombucha so that when poured into the minikeg, it was already cold. Then it sat in the fridge the whole time, other than when taking out for tasting.
2 - I did not do anything to purge the headspace. Didn't see any mention in if that in the video or the written instructions. Where are you seeing the 3 purge cycles?
Thanks!

Ah I see that is in the next video here (not the one I was looking at!):
https://www.growlerwerks.com/blogs/...onate-homebrew-using-ukeg-pressurized-growlerStep 9 - Purge oxygen from the head. Do this by turning the selector dial on until the regulator opens. You will hear a hiss of CO2 gas. Turn the selector dial off. Then un-screw the cap until the pressure is released. Repeat three times. This ensures no oxygen is left in the head space above your beer.

OK, then this seems like the next thing to try. Thanks!

 

[doug293cz]

1 - I first refridgerated the kombucha so that when poured into the minikeg, it was already cold. Then it sat in the fridge the whole time, other than when taking out for tasting.
2 - I did not do anything to purge the headspace. Didn't see any mention in if that in the video or the written instructions. Where are you seeing the 3 purge cycles?
Thanks!

Sorry, it was a subsequent video by uKeg.

It's at about 2 minutes in.

Edit: I see you found it before I finished my reply.

Brew on

 

[BBeerme]

When I was brewing, if memory serves, force carbonation took place quite quickly.

Siphon from carboy to cornelious. Pressurize through dip tube and purge air out through what would normally be the gas-in fitting. Let sit with possitive pressure CO2 overnight to chill. The next day crank up the CO2 to somewhere shy of the pressure relief. Add CO2 through the dip tube and shake baby, shake. When not taking any more CO2, stop shaking, leave pressurized, maybe go clean something, return in a bit and attach your beer out fitting with tap.

Do not attach CO2 in. Relieve keg pressure through gas-in fitting with something easy on the metal, like a piece of wood. When beer is pouring normal, attach your CO2 line at "normal" pressure, and your good to go. Except for the chilling overnight, the whole process is well under an hour.

 

[mac_1103]

Add CO2 through the dip tube and shake baby, shake.

That's burst carbonation, which is only one kind of force carbonation. Force carbonation is anything other than natural carbonation by fermentation. Connecting CO2 at 10 - 15 PSI and waiting 2 - 3 weeks is also force carbonation. This seems to cause a lot of confusion.

 

[BBeerme]

That's burst carbonation, which is only one kind of force carbonation. Force carbonation is anything other than natural carbonation by fermentation. Connecting CO2 at 10 - 15 PSI and waiting 2 - 3 weeks is also force carbonation. This seems to cause a lot of confusion.

2-3 Weeks? Ain't got no time fo' dat !!

 

[doug293cz]

When I was brewing, if memory serves, force carbonation took place quite quickly.

Siphon from carboy to cornelious. Pressurize through dip tube and purge air out through what would normally be the gas-in fitting. Let sit with possitive pressure CO2 overnight to chill. The next day crank up the CO2 to somewhere shy of the pressure relief. Add CO2 through the dip tube and shake baby, shake. When not taking any more CO2, stop shaking, leave pressurized, maybe go clean something, return in a bit and attach your beer out fitting with tap.

Do not attach CO2 in. Relieve keg pressure through gas-in fitting with something easy on the metal, like a piece of wood. When beer is pouring normal, attach your CO2 line at "normal" pressure, and your good to go. Except for the chilling overnight, the whole process is well under an hour.

Excess CO2 pressure + agitation is the easiest way to over carbonate beer. Yeah, it's fast, but dealing with over carbed kegs is a PITA.

The only way to really do it reliably is to weigh the keg as you carbonate. This requires a scale with a 60 - 70 lb min capacity, and gram (or ~0.1 oz) resolution. Beer after (closed) fermentation contains about 0.8 - 0.9 volumes of CO2. To carb to 2.5 volumes you need to add about 1.7 volumes of CO2. 1 volume is 0.264 oz/gal or 1.977 g/L, so 1.7 volume in 5 gal is 0.264 oz/gal * 5 gal * 1.7 = ~2.25 oz or 62 - 64 g. Weight the chilled keg before you start, and weigh frequently while agitating. When the keg gains the desired weight, then disconnect the CO2. You can then vent and repressurize at the chart pressure and serve. (Thanks to @bracconiere for alerting me to this method.)

Brew on

 

[BBeerme]

Excess CO2 pressure + agitation is the easiest way to over carbonate beer. Yeah, it's fast, but dealing with over carbed kegs is a PITA.

The only way to really do it reliably is to weigh the keg as you carbonate. This requires a scale with a 60 - 70 lb min capacity, and gram (or ~0.1 oz) resolution. Beer after (closed) fermentation contains about 0.8 - 0.9 volumes of CO2. To carb to 2.5 volumes you need to add about 1.7 volumes of CO2. 1 volume is 0.264 oz/gal or 1.977 g/L, so 1.7 volume in 5 gal is 0.264 oz/gal * 5 gal * 1.7 = ~2.25 oz or 62 - 64 g. Weight the chilled keg before you start, and weigh frequently while agitating. When the keg gains the desired weight, then disconnect the CO2. You can then vent and repressurize at the chart pressure and serve. (Thanks to @bracconiere for alerting me to this method.)

Brew on

I didn't have the fortune of knowing that formula, but I don't remember it being that much hassle. Only takes a couple of times before pressure and times are determined.

 

[gpeled]

Purging the oxygen did the trick, and now getting some real carbonation going on!
Thanks for the tips guys!