Limiting beer exposure to oxygen

[TennBrewer]

Lately I've been filling my corny kegs from the fermenter (primary and secondary) through the liquid post, the fermenter airlock is replaced with a hose to the gas post to equalize the pressure. I have read several posts where some brewers fill the receiving keg with StarSan and force it out using CO2 tank pressure. This could leave quite a bit of sanitizer in the bottom of the keg, I think. The intent is to limit the beer's exposure to oxygen. I was wondering why not just purge the receiving tank with CO2, which is heavier than oxygen thus the O2 rises to the top of the keg and is first forced out as the keg fills. I would think that this limits the O2 exposure, eliminates the StarSan fill and purge step, and leaves no residual sanitizer in the beer. I was curious if anyone has been doing this and are they satisfied with the results. I can say that my dry hopped beers have a stronger aroma when done this way as opposed to filling through the keg or fermenter opening.

 

[processhead]

Some say that there is enough turbulence when purging an empty keg with CO2 to cause some mixing with the air and a less than perfect purge of air and resulting oxygen left in the keg.
That is probably the rational behind CO2 purging a tank filled with a liquid like star-san instead.
However, at the present, I am doing it the way you described. When I fill the keg I make every effort to rack quietly without a lot of splashing. Filling through the liquid line is probably a good way to help ensure that.

 

[day_trippr]

A properly aligned full-length Out dip tube on a cornelius style keg isn't going to leave much fluid behind.
Literally, a couple of tablespoons worst-case.

fwiw, I do the Star San purge thing, and at the end I invert the keg, fill from the gas post and drain the air out via the beer post, rocking the keg a bit until the drain tubing runs bubble-free.
I set that keg on a bench and do a low-pressure (~1-2 psi) CO2 push back into my Star San bucket...

Cheers!

 

[rabeb25]

A simple trimmed gas tube to below flush of the keg and an inversion with a QD and blow out get everything.

 

[TennBrewer]

A properly aligned full-length Out dip tube on a cornelius style keg isn't going to leave much fluid behind.
Literally, a couple of tablespoons worst-case.

fwiw, I do the Star San purge thing, and at the end I invert the keg, fill from the gas post and drain the air out via the beer post, rocking the keg a bit until the drain tubing runs bubble-free.
I set that keg on a bench and do a low-pressure (~1-2 psi) CO2 push back into my Star San bucket...

Cheers!

Ok, there won't be much left if the dip tube is in order. However, I have trimmed about a half inch off my dip tubes so I wouldn't do the fill and purge thing, but your system is sound and seems to work for you just fine. It does sound like a lot of heavy lifting though, something I try to avoid with a bad back and all....

 

[Smellyglove]

Lately I've been filling my corny kegs from the fermenter (primary and secondary) through the liquid post, the fermenter airlock is replaced with a hose to the gas post to equalize the pressure. I have read several posts where some brewers fill the receiving keg with StarSan and force it out using CO2 tank pressure. This could leave quite a bit of sanitizer in the bottom of the keg, I think. The intent is to limit the beer's exposure to oxygen. I was wondering why not just purge the receiving tank with CO2, which is heavier than oxygen thus the O2 rises to the top of the keg and is first forced out as the keg fills. I would think that this limits the O2 exposure, eliminates the StarSan fill and purge step, and leaves no residual sanitizer in the beer. I was curious if anyone has been doing this and are they satisfied with the results. I can say that my dry hopped beers have a stronger aroma when done this way as opposed to filling through the keg or fermenter opening.

The star san purge thing doesn't leave any starsan left in the keg to worry about. It also cuts down on co2-usage, as you only have to purge the tiny headspace, and you push out the star san under low pressure. Purging an empty keg which has o2 in it, with co2, consumes way more co2 since that "co2 is heavier than air" theory is incorrect, and the gases will only mix. So you have to spend tonnes of co2 to get it dilluted to the point where there's "no" o2 left in the mix.

And, if you transfer beer into a secondary fermenter, and from that one into the keg, you are inducing oxygen at that step. There is no need to do a secondary if you brew normal beers.