[denny]

If the filtering is done under CO2 pressure in a closed system under CO2 pressure, where does the O2 come from?  Wouldn't there be some way to purge O2 before you filter? Not that I have any interest in filtering, but I'd like to know.

Yes, we have multiple sanitized / purged kegs and the transfer will will done under CO2 pressure. There will be close to zero oxygen in this procedure.

Regarding O2, I found multiple articles online that state it is little more than an old-wives-tale. Not old, actually, as this is a fairly new invention.

I have a 5D that was subjected to heavy O2 during the mash and sparge. And I mean HEAVY! It actually tastes great, might be one of my best efforts to date.

Another blind taste test show the participants could not detect the beer with O2. And interestingly, the person who ran the experiment could not distinguish the two beers apart.

Oxygen? Not worried about at all. Not in a 5, 10, or 20 gallon homebrew setting. In a commercial brewery, that might be another matter.

Ya know, if you look enough, you can find something on the internet to confirm whatever you think. The effects of O2 are not an old wive's tale. 

[Bel Air Brewing]

If the filtering is done under CO2 pressure in a closed system under CO2 pressure, where does the O2 come from?  Wouldn't there be some way to purge O2 before you filter? Not that I have any interest in filtering, but I'd like to know.

Yes, we have multiple sanitized / purged kegs and the transfer will will done under CO2 pressure. There will be close to zero oxygen in this procedure.

Regarding O2, I found multiple articles online that state it is little more than an old-wives-tale. Not old, actually, as this is a fairly new invention.

I have a 5D that was subjected to heavy O2 during the mash and sparge. And I mean HEAVY! It actually tastes great, might be one of my best efforts to date.

Another blind taste test show the participants could not detect the beer with O2. And interestingly, the person who ran the experiment could not distinguish the two beers apart.

Oxygen? Not worried about at all. Not in a 5, 10, or 20 gallon homebrew setting. In a commercial brewery, that might be another matter.

Ya know, if you look enough, you can find something on the internet to confirm whatever you think. The effects of O2 are not an old wive's tale.

I agree. That sword cuts in both directions.

[MDL]

Filtering beer is really not necessary in a home brewing setting. I used to filter beer, but it was a massive PITA. I still have my equipment but I never use it anymore. I can get polished beers in as little as 3 weeks from brew day. These beers are just as clear as any commercial beer, so why filter?

Years ago I set out to get clear beer and found out filtering was an unnecessary step. Clear beer starts in the mash tun. Good brewing practices throughout the brewing process will produce clear beer.

The biggest problem with filter, IMHO, is that it causes you to put your finished beer through a series of processes outside the fermentation vessel, the risk of oxidation is the over whelming reason I don't filter and recommend not to filter. I know some people say they don't have any oxygen problems with filtering, but I disagree. In the last couple of years I made a point to avoid oxygen ingress in finished beers by improving and updating vessels, doing closed transfers, spunding and extreme caution when adding anything to the finished beers. The difference has been stark. My beers are fresher longer, brighter flavors (hops especially) and greater depth in flavor. I believe filtering would set me back because it would introduce oxygen. Remember, it only takes oxygen levels to get up to 50-100 parts per billion to degrade finished beer.

My journey with home brewing has been similar to this.

[MDL]

If the filtering is done under CO2 pressure in a closed system under CO2 pressure, where does the O2 come from?  Wouldn't there be some way to purge O2 before you filter? Not that I have any interest in filtering, but I'd like to know.

I think it depends on how the purging is done. For instance, pressurizing an empty corny keg with co2 then releasing and repeating won’t completely purge the keg of atmosphere. I noticed an improvement in the shelf life of my keg beer when I started filling the receiving keg to the rim with sanitizer and then pushing all that out with co2 before filling said keg counter pressure.

[Bel Air Brewing]

If the filtering is done under CO2 pressure in a closed system under CO2 pressure, where does the O2 come from?  Wouldn't there be some way to purge O2 before you filter? Not that I have any interest in filtering, but I'd like to know.

I think it depends on how the purging is done. For instance, pressurizing an empty corny keg with co2 then releasing and repeating won’t completely purge the keg of atmosphere. I noticed an improvement in the shelf life of my keg beer when I started filling the receiving keg to the rim with sanitizer and then pushing all that out with co2 before filling said keg counter pressure.

Oxygen problem solved…just in case it ever existed.

And likewise, we noticed a huge increase in shelf life of our filtered beers.

[HighVoltageMan!]

If the filtering is done under CO2 pressure in a closed system under CO2 pressure, where does the O2 come from?  Wouldn't there be some way to purge O2 before you filter? Not that I have any interest in filtering, but I'd like to know.

I think it depends on how the purging is done. For instance, pressurizing an empty corny keg with co2 then releasing and repeating won’t completely purge the keg of atmosphere. I noticed an improvement in the shelf life of my keg beer when I started filling the receiving keg to the rim with sanitizer and then pushing all that out with co2 before filling said keg counter pressure.

^^^^ Bang! It's not perfect, but way better than just purging with co2.

[HighVoltageMan!]

If the filtering is done under CO2 pressure in a closed system under CO2 pressure, where does the O2 come from?  Wouldn't there be some way to purge O2 before you filter? Not that I have any interest in filtering, but I'd like to know.

Even the best efforts to remove oxygen with co2 will leave some oxygen behind. The point is not to get to perfection, which is impossible, the point is to get as low as possible. Without a DO meter there is really no way to know how much ingress occurs, but from my reading and research it's not very hard to hit above 100ppb. Most breweries that look into their handling of beer are surprised to see +100-200ppb of oxygen in packaged beer; almost all breweries struggle with this and it has a huge impact on the quality of beer. Most homebrewers can't come close to these numbers, but it begs the question; Why tempt fate? Leave well enough alone and enjoy your unfiltered beer. Plus it's easier.

[denny]

If the filtering is done under CO2 pressure in a closed system under CO2 pressure, where does the O2 come from?  Wouldn't there be some way to purge O2 before you filter? Not that I have any interest in filtering, but I'd like to know.

I think it depends on how the purging is done. For instance, pressurizing an empty corny keg with co2 then releasing and repeating won’t completely purge the keg of atmosphere. I noticed an improvement in the shelf life of my keg beer when I started filling the receiving keg to the rim with sanitizer and then pushing all that out with co2 before filling said keg counter pressure.

of course

[denny]

If the filtering is done under CO2 pressure in a closed system under CO2 pressure, where does the O2 come from?  Wouldn't there be some way to purge O2 before you filter? Not that I have any interest in filtering, but I'd like to know.

Even the best efforts to remove oxygen with co2 will leave some oxygen behind. The point is not to get to perfection, which is impossible, the point is to get as low as possible. Without a DO meter there is really no way to know how much ingress occurs, but from my reading and research it's not very hard to hit above 100ppb. Most breweries that look into their handling of beer are surprised to see +100-200ppb of oxygen in packaged beer; almost all breweries struggle with this and it has a huge impact on the quality of beer. Most homebrewers can't come close to these numbers, but it begs the question; Why tempt fate? Leave well enough alone and enjoy your unfiltered beer. Plus it's easier.

I agree with the last couple sentences, but it still doesn't answer the question of where O2 would come from in a properly purged, closed system.

[ynotbrusum]

I suppose one could attempt to measure ppb of O2 and compare bottled CO2 from the tank (low, but some O2) versus using the natural CO2 from fermentation to push out the sanitizer or O2 in the corny.  Further, if done properly and timely, spunding reliably takes care of most (if not all) of the O2 in the receiving keg.  It all depends on how far you want to go to minimize O2 ingress.

[Bel Air Brewing]

If the filtering is done under CO2 pressure in a closed system under CO2 pressure, where does the O2 come from?  Wouldn't there be some way to purge O2 before you filter? Not that I have any interest in filtering, but I'd like to know.

Even the best efforts to remove oxygen with co2 will leave some oxygen behind. The point is not to get to perfection, which is impossible, the point is to get as low as possible. Without a DO meter there is really no way to know how much ingress occurs, but from my reading and research it's not very hard to hit above 100ppb. Most breweries that look into their handling of beer are surprised to see +100-200ppb of oxygen in packaged beer; almost all breweries struggle with this and it has a huge impact on the quality of beer. Most homebrewers can't come close to these numbers, but it begs the question; Why tempt fate? Leave well enough alone and enjoy your unfiltered beer. Plus it's easier.

I agree with the last couple sentences, but it still doesn't answer the question of where O2 would come from in a properly purged, closed system.

Answer - it doesn't.

[narvin]

If the filtering is done under CO2 pressure in a closed system under CO2 pressure, where does the O2 come from?  Wouldn't there be some way to purge O2 before you filter? Not that I have any interest in filtering, but I'd like to know.

Yes, we have multiple sanitized / purged kegs and the transfer will will done under CO2 pressure. There will be close to zero oxygen in this procedure.

Regarding O2, I found multiple articles online that state it is little more than an old-wives-tale. Not old, actually, as this is a fairly new invention.

I have a 5D that was subjected to heavy O2 during the mash and sparge. And I mean HEAVY! It actually tastes great, might be one of my best efforts to date.

Another blind taste test show the participants could not detect the beer with O2. And interestingly, the person who ran the experiment could not distinguish the two beers apart.

Oxygen? Not worried about at all. Not in a 5, 10, or 20 gallon homebrew setting. In a commercial brewery, that might be another matter.

There's a difference between hot side and post fermentation oxygen, though.  Even if HSA is a myth, I wouldn't want to subject any beer to a lot of O2 at kegging
.

[Bel Air Brewing]

If the filtering is done under CO2 pressure in a closed system under CO2 pressure, where does the O2 come from?  Wouldn't there be some way to purge O2 before you filter? Not that I have any interest in filtering, but I'd like to know.

Yes, we have multiple sanitized / purged kegs and the transfer will will done under CO2 pressure. There will be close to zero oxygen in this procedure.

Regarding O2, I found multiple articles online that state it is little more than an old-wives-tale. Not old, actually, as this is a fairly new invention.

I have a 5D that was subjected to heavy O2 during the mash and sparge. And I mean HEAVY! It actually tastes great, might be one of my best efforts to date.

Another blind taste test show the participants could not detect the beer with O2. And interestingly, the person who ran the experiment could not distinguish the two beers apart.

Oxygen? Not worried about at all. Not in a 5, 10, or 20 gallon homebrew setting. In a commercial brewery, that might be another matter.

There's a difference between hot side and post fermentation oxygen, though.  Even if HSA is a myth, I wouldn't want to subject any beer to a lot of O2 at kegging
.

I agree, of course. We go to great extremes to prevent oxygen in our packaged beer.

[HighVoltageMan!]

If the filtering is done under CO2 pressure in a closed system under CO2 pressure, where does the O2 come from?  Wouldn't there be some way to purge O2 before you filter? Not that I have any interest in filtering, but I'd like to know.

Even the best efforts to remove oxygen with co2 will leave some oxygen behind. The point is not to get to perfection, which is impossible, the point is to get as low as possible. Without a DO meter there is really no way to know how much ingress occurs, but from my reading and research it's not very hard to hit above 100ppb. Most breweries that look into their handling of beer are surprised to see +100-200ppb of oxygen in packaged beer; almost all breweries struggle with this and it has a huge impact on the quality of beer. Most homebrewers can't come close to these numbers, but it begs the question; Why tempt fate? Leave well enough alone and enjoy your unfiltered beer. Plus it's easier.

I agree with the last couple sentences, but it still doesn't answer the question of where O2 would come from in a properly purged, closed system.

Your assuming perfection in purging. It isn’t perfect, you have mere mortals involved.  Even a small amount of oxygen can produce 50 part s per billion. If Weinhenstephan and Sierra Nevada has trouble with it, I’ll have even a bigger problem with it.

[MDL]

If beverage grade CO2 is 99.9% pure is it possible that one could oxidize their beer just by force carbonating it or at least neutralize any antioxidants naturally present prior to carbonating?