Starsan foam blanket to prevent oxidation

[Holden Caulfield]

So I have a crazy idea to run by anyone who cares to comment (I have way too much time on my hands)

My process today is to use CO2 to push beer into sanitized kegs that have not been purged, minimizing oxidation from splashing, chance of infection, and saving my back from lifting the full fermenter out of my chest freezer. Call me lazy and cheap, but I just don't want to go the extra oxygen minimization mile by either filling up my keg with 5 gallons of Starsans then pushing it out with CO2 into a storage bucket for reuse, or setting up a system to capture the fermentation gas in a sanitized keg.

Given that the often relied on CO2 blanket is a myth, what if, after sanitizing and adding conditioning syrup to the keg, one whips up a half gallon of Starsan foam by bubbling CO2 through Starsans and then displaces the air at the bottom of the keg with the foam. This should be easy as both the Starsans and CO2 are in use during packaging day. Then, as the beer enters the keg through the out diptube, the Starsans CO2 foam would actually create a CO2 barrier raft that will float up with the beer, displacing the air and creating the elusive CO2 blanket we wish existed. Net benefit - only 1/2 gallon rather than 5 gallons of CO2 used as well as no additional vessels required.

Do you think it would work or am I crazy?

 

[McKnuckle]

I don't know about the CO2 protection part, but the foam does eventually settle back into liquid StarSan. Do you want that in your beer?

 

[BrewZer]

I've never used the stuff, but I wouldn't do it. It's a sanitizer, and just because it's tasteless and odorless (at recommended dilution levels) doesn't mean it won't screw up your beer. That foam won't last forever.

 

[mcmeador]

Why would the alternative be mixing up 5 gallons of Starsan for your keg? I only do 2 1/2 gallons, close the keg, shake it up, and then let it stand right-side up and upside down for a few minutes each for good measure. Then I push out with CO2. I’m no scientist, so I don’t know if that uses the same amount of CO2, but it would use less Starsan. You really don’t even need 2.5 gallons.

Better yet, you surely are using Starsan on brew day. Why don’t you just save it in a closed container to use to sanitize the kegs on kegging day so you don’t have to mix up more? If it’s been more than a few weeks, you might want to check it with PH strips to make sure it’s still good.

 

[Qhrumphf]

Why would the alternative be mixing up 5 gallons of Starsan for your keg? I only do 2 1/2 gallons, close the keg, shake it up, and then let it stand right-side up and upside down for a few minutes each for good measure. Then I push out with CO2. I’m no scientist, so I don’t know if that uses the same amount of CO2, but it would use less Starsan. You really don’t even need 2.5 gallons.

Better yet, you surely are using Starsan on brew day. Why don’t you just save it in a closed container to use to sanitize the kegs on kegging day so you don’t have to mix up more? If it’s been more than a few weeks, you might want to check it with PH strips to make sure it’s still good.

If you're liquid purging, that keg needs to be entirely full of liquid. Your keg would still be halfish (slightly more than) full of air. People use fermentation to purge a) because it doesn't require paying for CO2 and b) because it's way way way more pure than bottled CO2 is.

To the OP, I'm not sure how you plan to get the foam into your keg. Are you planning to add sanitizer itself to your priming solution? A little residual foam is not an issue. What you're proposing I wouldn't want to do.

If you're already set up to do a proper purge and *closed* gas transfer, just do that. And transfer your beer a little earlier (aim for 3-4 SG points above your target FG), let it finish in the keg. That way you don't even need the priming solution.

 

[mcmeador]

If you're liquid purging, that keg needs to be entirely full of liquid. Your keg would still be halfish (slightly more than) full of air. People use fermentation to purge a) because it doesn't require paying for CO2 and b) because it's way way way more pure than bottled CO2 is.

Would the air in the keg not be replaced by the CO2 as well and pushed out with the sanitizer?

 

[marc1]

Would the air in the keg not be replaced by the CO2 as well and pushed out with the sanitizer?

In your example, the air in the keg is diluted with the CO2 that you push out the sanitizer with, leaving plenty of oxygen in there.
If you want to remove oxygen to negligible levels, it takes 13 full purges at 30PSI. A small headspace is much better for CO2 use with this method.

 

[mcmeador]

In your example, the air in the keg is diluted with the CO2 that you push out the sanitizer with, leaving plenty of oxygen in there.
If you want to remove oxygen to negligible levels, it takes 13 full purges at 30PSI. A small headspace is much better for CO2 use with this method.

Ah, ok. Well disregard my original post then. I suppose I’m still exposing my beer to limited oxygen, though, since any CO2/air mixture in the keg is pushed out of the top as the beer is pushed in from the bottom, and then the headspace is purged. But I definitely see how a full keg is better and will do that going forward. Sorry for the bad advice.

 

[Qhrumphf]

What you're doing is better than nothing, but definitely could be improved.

 

[jddevinn]

The "foam" is a little bit StarSan and a lot of CO2. The keg is full of air (part we care most is O2). By the time that the foam "purges" the keg it will be a little bit StarSan and a lot O2. The CO2 in the foam will immediately start to mix with the air as soon as it enters the keg.

You can use StarSan over and over if you make it with RO or similar water.....

 

[Bobby_M]

So I have a crazy idea
Call me lazy and cheap,
Do you think it would work or am I crazy?

You are crazy and cheap. With all the effort brewing and fermenting and packaging, you're damaging your beer for hardly any savings. If you get yourself a 20LB CO2 tank, the amount of CO2 used in a full liquid purge is pennies and takes all of 10 minutes to perform. If you are more cheap than lazy, the direction of fermentation CO2 through a sanitized keg is only slightly more setup for the same effect. Any of it is worth is if you want less stale beer.

 

[Bilsch]

Call me lazy and cheap, but I just don't want to go the extra oxygen minimization mile by either filling up my keg with 5 gallons of Starsans then pushing it out with CO2 into a storage bucket for reuse, or setting up a system to capture the fermentation gas in a sanitized keg.

A system for purging the keg with ferment CO2 is no more complicated then two pieces of tubing and a couple quick disconnects.

 

[Holden Caulfield]

Thanks all, just trying to come up with a way to reduce oxygen with minimum effort - the 57 year old sciatic back gets sore quick.

A system for purging the keg with ferment CO2 is no more complicated then two pieces of tubing and a couple quick disconnects.

^This is the approach I will be taking.

 

[Bilsch]

Thanks all, just trying to come up with a way to reduce oxygen with minimum effort - the 57 year old sciatic back gets sore quick.

It’s best to use oxygen barrier tubing for the connection between the fermenter and keg to be purged.