A Thought On Bottling vs. Kegging

Last night I was reading in the Brewing Elements series, “Water”, that the acceptable oxygen levels in commercially packaged beers were about 50 parts per billion.  Yes, you read the denominator right, billion.  This is to prevent staling of the finished product.  While their supply chain is considerably longer than mine, it got me thinking about the difference between kegging with forced carbonation and bottling.  If you naturally condition in the keg you should be able to consider it bottling for this purpose.

With forced carbonation, you may or may not be driving off all the oxygen.  Henry’s Law states that the partial pressures of gas in solution add up to the pressure on the solution so when forcing carbon dioxide into your beer under pressure, you may not be forcing oxygen out since the pressure is high enough it could allow both gasses to remain.  If oxygen is not forced out, you’re exposing your beer to oxidization and all the nasty flavors that brings, sherry and wet cardboard.  At Homebrewer’s Night I’ve tasted oxidized beers but have never thought to ask if the brewer filled the bottles from kegs so I’m simply guessing here.  But my bottle conditioned beers have never had that distinctive oxidation flavor and I’ve kept some of them upwards of 18 months.

I’m guessing that here, too, yeast is your friend.  It’s alive and respiring down there in the bottom of that bottle, scavenging oxygen from its environment every chance it gets.  So I’m thinking the yeast keep the oxygen level below that which can cause staling.  Of course I don’t have equipment lying around to test this but simply logically, when it comes to oxygen in the beer, the advantage goes to bottle conditioning.


One thought on “A Thought On Bottling vs. Kegging

  1. My thoughts.

    In both situations, if proper care is taken, there should be little to no O2 in the finished beer after fermentation. The yeast would have absorbed all it could, and any remaining in the head space would have been driven off by the CO2 produced. Therefore the only significant O2 in solution would be that which is introduced in the transfer to package.
    True, any O2 introduced by bottling could be used by the yeast as it ferments the priming sugar, but this is a minor activity, using only a fraction of the yeast, as compared to the main fermentation.
    O2 introduced at kegging can be kept to a minimum in the transfer with steps such as pre-filling the keg with CO2, and purging the keg head space immediately afterwords. The O2 that enters the carboy as the beer evacuates would still sit on top of a layer of denser CO2. All that could come in contact would be the O2 in the siphon line, and you could purge that as well with beer before placing the tube in the keg.
    Bottling that uses a transfer to a bucket first for priming, could introduce more O2 than kegging, one could argue.
    On top of all that, the minor amount of O2 that could contact the finished beer in either process, would only truly effect the staleing process, and that only of beers stored long term, in warm environs. Cellered properly, this effect is reduced if the beer is consumed in a reasonable time. More so at cold temps where kegs are usually kept. Once I keg the beer, it never warms again, except in my glass. I may purposely keep it warm if I’m dry hopping for instance, but only for a week or so , and then its kept cold.

    Does any of my argument have value?

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