Why do we worry about oxidation with hand pump taps?

[mkory]

I've been thinking this one over for a while now...

You always hear that if you hand pump a keg, the beer is quickly oxidized and will go stale fast, but there are a few things that just don't make sense to me.

1.) Is there not still a layer of co2 on the beer from the factory (to keep it from oxidizing before it's sold? If so, wouldn't that protect the beer when air is pumped into the keg?



2.) If you keg, but are forced to use a hand pump...
Oxidation of our wort is not a concern because the amount of oxygen that can dissolve in beer is relatively low compared to the amount of co2 that will carry that o2 out during fermentation. If that's the case, why not force the (hand pumped tap and now oxidized) beer to become flat, carrying the dissolved o2 out of the beer (like fermentation does), then re carb?

 

[Yuri_Rage]

Once you start pumping air into the keg, you are introducing oxygen (and every other gas in the atmosphere, but those are mostly non-reactive). Gases mix quickly in confined spaces, so that "blanket" of CO2 does not exist in the presence of other gases.

It takes a lot of CO2 to carbonate beer, but very little O2 to give it an oxidized flavor. Beer does not have to be effervescent with oxygen to become stale. Once beer is oxidized, the process is irreversible. Oxidation is a chemical reaction, not just the mere presence of oxygen.

 

[Edcculus]

Not trying to sound like an ass, but you are way off base. Like Yuri said, once you pump in atmospheric air all the empty space in a keg mixes.

Also, oxygenating wort prior to pitching yeast is the right thing to do. Not because the CO2 will carry it off. Because yeast need oxygen in the growth/lag phase to properly build sterols for healthy cell walls. Yeast will scavenge available oxygen before the fermentation part of their life cycle actually starts. Any oxygen post fermentation will eventually lead to staleness and oxidized flavors.

Another thing with a hand pump, is that you can't be sure exactly what else is being pumped in there unless you have a hepa filter attached. Its very likely you are pumping in a good bit of wild yeast, some molds and even lactobacillus. Besides oxidizing the beer, you are pumping in a lot of potential spoilage organisms.

 

[TXCrash]

I've been thinking this one over for a while now...

You always hear that if you hand pump a keg, the beer is quickly oxidized and will go stale fast, but there are a few things that just don't make sense to me.

1.) Is there not still a layer of co2 on the beer from the factory (to keep it from oxidizing before it's sold? If so, wouldn't that protect the beer when air is pumped into the keg?



2.) If you keg, but are forced to use a hand pump...
Oxidation of our wort is not a concern because the amount of oxygen that can dissolve in beer is relatively low compared to the amount of co2 that will carry that o2 out during fermentation. If that's the case, why not force the (hand pumped tap and now oxidized) beer to become flat, carrying the dissolved o2 out of the beer (like fermentation does), then re carb?

Apparenly you've never had "morning after the kegger" beer. Try it and report back...

 

[david_42]

We don't worry about oxidation in the fermenter or clearing tank, as the CO2 is being created in the first case and in the second, we are not disturbing the CO2 blanket. The difference in weight between CO2 and air isn't all that great. Drawing down a keg brings air into the headspace, generally through a small opening and at a high velocity. This makes for strong mixing of the gases and oxygen reaches the beer.

If the keg was wide open and stored in an space with no air currents, then the CO2 blanket would have some chance of remaining stable.

 

[kinison_fan]

Besides, hand pumps are typically only used for rentals, "party" kegs that are tapped and pretty much continously consumed until empty. The beer is consumed before it goes bad/oxidizes-the hand pump is only pushing the beer through the lines.

As mentioned above, next morning (or even two days later), the beer is "bad" and getting worse.

 

[mkorpal]

I can see this being a problem if you are slowly drinking a keg over the course of a month. But at a party, I really doubt you can oxidize a beer in one day? Everything I know about brewing tells me that oxidizing a beer takes a long time.

 

[Schlenkerla]

This problem could be rectified if breweries sold beer in collapsible poly pins. Then you could attach a beer engine faucet to pull a vacuum as you serve the beer the pin collapses w/o any new air introduction.

This is what I have going in my apartment now (2nd residence Mon-Thurs).

2nd pic, courtesy of BioBeing...

https://www.homebrewtalk.com/f13/how-high-prime-polypin-162820/index4.html#post1909321

https://www.homebrewtalk.com/f51/beer-engine-jockey-box-like-beer-engine-161736/