What steps do you follow to dry hop in a CO2 purged keg?

[Bmcclure8]

If I understand correctly, many people push their beers from carboys or conical into a co2 purged keg. If the process to purge the keg is fill it with star san and the push all the star san with co2 so you have five gallons of CO2, you end up with a pressurized keg. Ready to receive beer pushed by co2.

I must be missing something but when and how do you add the dry hops? Do you open the keg and drop them in assuming the heavier CO2 will stay in the keg? Add them after you push the beer over (which seems to defeat purpose of avoiding the beer exposures to oxygen).

What’s your process?

Also I’ve never pushed beer out of fermenters with CO2 and I have a glass carboy. Am I asking for trouble if I keep it at 1psi?

 

[Hwk-I-St8]

First, I do the vast majority of my dry hopping in the primary (I brew mostly NEIPAs). Second, I don't do the "fill the keg with star-san solution and push out with CO2"...mostly because I don't want residual Star San solution in my keg and also because it literally cuts in half how many kegs I can serve with a bottle of CO2.

I have not had any problems with oxidation so far, even with bottles filled from the keg that were 2 months old. I sent a 2 month old bottle to a friend on the east coast and his first comment was how it show no signs of oxidation...a notorious issue for NEIPAs. For that reason, I don't feel like my process is flawed. I will say that others seem to have issues unless they take extreme steps, so I really can't answer what's the difference.

My standard process is this:

I dry hop about 24 hours after pitch, when the really active fermentation is winding down. After I determine fermentation is complete (usually about 4-5 days with the 1318 I usually use and the pitch rate I use), I cold crash. To cold crash, I remove the blow off tube, replace it with an S style airlock filled with vodka and drop the temp. I don't take any extraordinary precautions to keep O2 out of the fermenter.

After a couple days cold crashed, I clean and sanitize my keg, dumping all the star san out and reassemble. (I use sanke kegs most of the time). Prior to reassembly, this is where I add in-keg hops (I've only done that once). I put a coupler on that has the check ball removed from the serving port, connect CO2 tank to the liquid out port and run CO2 at 2 psi for about a minute. That pushes CO2 in at the bottom and vents out the top. For a corny, you'd need to attach a connector to the gas port so that the gas can escape. I then connect the CO2 to my fermenter along with a racking cane that I connect to the serving port of the keg coupler. The CO2 pressure starts a siphon into the serving port. This fills from the bottom up. Once the siphon is going, I replace the CO2 into the fermenter with a hose coming from the CO2 port of the keg coupler so that the gas displaced in the keg is fed into the fermenter. Let the siphon complete and the keg is filled.

At this point there's very little dead space in the keg, but I pressurize to 20 psi and pull the vent valve 5 times the replace the gas in the headspace of the keg. Then force carb as usual.

There are many who do the whole LODO thing and seem to need that to get drinkable beer with a reasonable shelf life. I haven't had any issues so far with NEIPA's and the porter I've been serving since November. For that reason I have to say YMMV, but this process works perfectly for me.

The only change I've considered is getting a fermenter with a drain valve to skip the whole siphon part...then I can just drain instead of using CO2 to initiate the siphon.

I wish you the best of luck and happy brewing.

 

[popsicleian]

I have tackled this two different ways:

1) After fermentation is complete, add dry hops to sanitized serving keg in bag or mesh canister, close it up, do 7 or so purge cycles at 30 PSI. This won't remove all of the oxygen, but it removes quite a bit. It also uses a ton of CO2. After purging, I rack my beer into the sealed keg through the liquid out post.

2) As active fermentation is just getting underway (I usually ferment in kegs), add dry hops to a separate sanitized serving keg in bag or mesh canister. Hook up gas in on fermenting keg to liquid out on serving keg, allow CO2 from fermentation to purge the serving keg (I'll hook up a disconnect on the gas in of the serving keg with tubing that leads to a container of starsan to make it a closed system). I'll leave it hooked up for a couple of days, then remove the serving keg, add a few PSI to make sure the lid stays sealed, and put in the keg fridge until fermentation is complete. Once fermentation is complete, I rack my beer into the sealed serving keg through the liquid out post.

I don't always have a serving keg ready and available when I'm starting fermentation, but if I do I prefer method #2.

 

[beernutz]

I have placed dry hops in a SS mesh cylinder and added that to the corny. I then repeatedly fill and purge the corny with C02, usually 7 to 10 times.

I don't think this method is as thorough for purging air as when I've filled kegs with starsan solution and then pushed it out with C02 but beers done with the first method stay drinkable for the few months they last at my house so the fill and purge method satisfies me.

An alternative is to dry hop in the primary after fermentation has dropped off.

 

[eric19312]

I assume @doug293cz will be here soon with his calculations around keg purging. Pushing star san out of a keg with CO2 actually uses much less CO2 than multiple fill purge cycles, and seven fill purge cycles is nowhere near enough times to get to a keg with similar level of O2 as you can get with a single star san flush. If you are concerned about residual star san you can always do a star san rinse, then fill with clean dechlorinated water and then pump the water out with CO2.

here is what I do for keg hopping. I am open to better ideas but I'm probably not going to go through 30 cycles of purging.

I fill my keg all the way up with starsan so it is coming out the PRV. Then I push the star san out the liquid out line using about 2 psi. Then I fill the keg using about 2 PSI to push beer from my Spiedel fermentor into the keg. I now have a very full keg with little or no Oxygen in it. I then - ready for this - open the keg and carefully so as not to splash lower a stainless steel tea ball with 1 oz pellet hops into the beer. I then close the keg and do about 10 purge and release cycles. How is this better than adding the hops and purging the keg? It has to do with volume. I'm purging the head space, not the whole keg. I fill the keg full of beer, the headspace is about a quart to a half gallon. So each purge I do is only using 5-10% of the CO2 you are using if you are doing a full keg purge.

 

[brandonlovesbeer]

I’m so confused at the process described in the initial question.

Dry hop in primary and leave for a predetermined ed number of days.
Then...
Just use as an auto siphon to fill the keg.
Then carbonate. Easy peezy lemon squeezy

 

[beernutz]

I believe 7 CO2 purges at 25 psi will result in a >99.9% CO2 concentration.

 

[grampamark]

I believe 7 CO2 purges at 25 psi will result in a >99.9% CO2 concentration.

I've read that, as well. The LODO disciples claim that the remaining .1% dissolved oxygen is enough to trigger the Oxidation Apocalypse. The folks who are doing low-ish oxygen cold side processes say that pushing sanitizer (or plain water in a sanitized keg) gets the same results and uses a fraction of the Co2 as repeatedly purging. Long thread about that here.

Mark

 

[eric19312]

I've read that, as well. The LODO disciples claim that the remaining .1% dissolved oxygen is enough to trigger the Oxidation Apocalypse. The folks who are doing low-ish oxygen cold side processes say that pushing sanitizer (or plain water in a sanitized keg) gets the same results and uses a fraction of the Co2 as repeatedly purging. Long thread about that here.

Mark

Since @doug293cz didn't manage to make it over here I will add his table. I understand this is calculated based on the dilution of gas.

7 purges at 25 psi will get you down to 200 ppm O2 in the headspace.

How big is your headspace?
If you are purging a full keg your headspace is about 5.5 gallons.
Using this calculator https://www.omnicalculator.com/physics/ideal-gas-law
assuming 70F room temperature operation, each purge uses 1.47 mols of CO2.
CO2 has a molecular weight of 44 g/mol so each purge is using about 65 grams CO2.
7 purges is about 450 grams CO2 which is almost exactly 1 pound of CO2.

Filling that same keg 1 time with CO2 at 3psi uses 0.176 mols CO2 which is 7.7 grams or 0.016 pounds. If I then open the full keg and add dry hops and then purge the head space with 7 blasts of 25 PSI I will use about 0.1 lb of CO2 to purge the head 1/2 gallon head space in addition to what I used to purge the keg.

 

[doug293cz]

I have tackled this two different ways:

1) After fermentation is complete, add dry hops to sanitized serving keg in bag or mesh canister, close it up, do 7 or so purge cycles at 30 PSI. This won't remove all of the oxygen, but it removes quite a bit. It also uses a ton of CO2. After purging, I rack my beer into the sealed keg through the liquid out post.

2) As active fermentation is just getting underway (I usually ferment in kegs), add dry hops to a separate sanitized serving keg in bag or mesh canister. Hook up gas in on fermenting keg to liquid out on serving keg, allow CO2 from fermentation to purge the serving keg (I'll hook up a disconnect on the gas in of the serving keg with tubing that leads to a container of starsan to make it a closed system). I'll leave it hooked up for a couple of days, then remove the serving keg, add a few PSI to make sure the lid stays sealed, and put in the keg fridge until fermentation is complete. Once fermentation is complete, I rack my beer into the sealed serving keg through the liquid out post.

I don't always have a serving keg ready and available when I'm starting fermentation, but if I do I prefer method #2.

Personally, I believe your method #2 is about the best process possible. I did a detailed analysis of residual O2 in headspaces after fermentation, and purging a keg with the CO2 from a full fermentation gives very low (ppb) levels of O2.

I assume @doug293cz will be here soon with his calculations around keg purging. Pushing star san out of a keg with CO2 actually uses much less CO2 than multiple fill purge cycles, and seven fill purge cycles is nowhere near enough times to get to a keg with similar level of O2 as you can get with a single star san flush. If you are concerned about residual star san you can always do a star san rinse, then fill with clean dechlorinated water and then pump the water out with CO2.

here is what I do for keg hopping. I am open to better ideas but I'm probably not going to go through 30 cycles of purging.

I fill my keg all the way up with starsan so it is coming out the PRV. Then I push the star san out the liquid out line using about 2 psi. Then I fill the keg using about 2 PSI to push beer from my Spiedel fermentor into the keg. I now have a very full keg with little or no Oxygen in it. I then - ready for this - open the keg and carefully so as not to splash lower a stainless steel tea ball with 1 oz pellet hops into the beer. I then close the keg and do about 10 purge and release cycles. How is this better than adding the hops and purging the keg? It has to do with volume. I'm purging the head space, not the whole keg. I fill the keg full of beer, the headspace is about a quart to a half gallon. So each purge I do is only using 5-10% of the CO2 you are using if you are doing a full keg purge.

Sorry, didn't see the alert for your mention, so I showed up late.

I have been using the same method as you, but plan to switch to method #2 detailed by @popsicleian.

I believe 7 CO2 purges at 25 psi will result in a >99.9% CO2 concentration.

Yes, but 0.1% of the original O2 is 200 ppm. Commercial brewers target less than 150 ppb (0.15 ppm.)

Since @doug293cz didn't manage to make it over here I will add his table. I understand this is calculated based on the dilution of gas.

View attachment 553419

7 purges at 25 psi will get you down to 200 ppm O2 in the headspace.

How big is your headspace?
If you are purging a full keg your headspace is about 5.5 gallons.
Using this calculator https://www.omnicalculator.com/physics/ideal-gas-law
assuming 70F room temperature operation, each purge uses 1.47 mols of CO2.
CO2 has a molecular weight of 44 g/mol so each purge is using about 65 grams CO2.
7 purges is about 450 grams CO2 which is almost exactly 1 pound of CO2.

Filling that same keg 1 time with CO2 at 3psi uses 0.176 mols CO2 which is 7.7 grams or 0.016 pounds. If I then open the full keg and add dry hops and then purge the head space with 7 blasts of 25 PSI I will use about 0.1 lb of CO2 to purge the head 1/2 gallon head space in addition to what I used to purge the keg.

Nice jobs with the calcs!

Brew on

 

[troglodytes]

I assume @doug293cz will be here soon with his calculations around keg purging. Pushing star san out of a keg with CO2 actually uses much less CO2 than multiple fill purge cycles, and seven fill purge cycles is nowhere near enough times to get to a keg with similar level of O2 as you can get with a single star san flush. If you are concerned about residual star san you can always do a star san rinse, then fill with clean dechlorinated water and then pump the water out with CO2.

here is what I do for keg hopping. I am open to better ideas but I'm probably not going to go through 30 cycles of purging.

I fill my keg all the way up with starsan so it is coming out the PRV. Then I push the star san out the liquid out line using about 2 psi. Then I fill the keg using about 2 PSI to push beer from my Spiedel fermentor into the keg. I now have a very full keg with little or no Oxygen in it. I then - ready for this - open the keg and carefully so as not to splash lower a stainless steel tea ball with 1 oz pellet hops into the beer. I then close the keg and do about 10 purge and release cycles. How is this better than adding the hops and purging the keg? It has to do with volume. I'm purging the head space, not the whole keg. I fill the keg full of beer, the headspace is about a quart to a half gallon. So each purge I do is only using 5-10% of the CO2 you are using if you are doing a full keg purge.

I'm going to try this method next time, seems like such common sense get the better part of all worlds, keg hopping, lower CO2 usage and low O2. Would this be even more successful if you transferred to keg with 1-2 points to go in fermentation so that it continued to ferment in the keg building CO2 pressure in the head space, or would releasing the PRV to add you dry hops expel too much of your aromatics to be worth trying?

 

[eric19312]

I'm going to try this method next time, seems like such common sense get the better part of all worlds, keg hopping, lower CO2 usage and low O2. Would this be even more successful if you transferred to keg with 1-2 points to go in fermentation so that it continued to ferment in the keg building CO2 pressure in the head space, or would releasing the PRV to add you dry hops expel too much of your aromatics to be worth trying?

Sure that would work. Sometimes I’ll add a bit of sugar with dry hops to encourage some yeast activity. But mostly not as the beer is usually cold (cold crashed for 2 days before kegging) when I keg and goes straight into keezer. If I have a keg that will be conditioning at room temp I do prefer at least a partial priming sugar carbonation.