Oxygen is the enemy of finished beer, and hence brewers often take measures to reduce the risk of oxidation, with one technique involving purging kegs with CO2 prior to packaging. Curious if this step has a meaningful impact, we performed a variety of exBEERiments to find out!
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10 thoughts on “The Brülosophy Show: Does PURGING THE KEG Have A Perceptible Impact On Beer? | exBEERiments”
Yes, the answer is yes. Moreso for high hopped beers
I hook up a gas line to the out post and purge with CO2 from the bottom up letting the air escape via the pressure relief valve. I close the valve and let the empty purged keg come up to leak test pressure and leave it alone for a while. In my mind, any O2 will rise to the top and vent when I release the pressure prior to transfer. I carbonate via Quick Carb and usually manage to remind myself to purge the Quick Carb hoses prior to connection.
I am pleased to learn that only the highly hopped NEIPA was sensitive enough to oxygen that people could detect a difference. I have a graph that shows the number of times an empty keg must be purged with carbon dioxide (CO2) at various pressures for oxygen (O2) to drop below various ppm concentrations. Example: try 13 purges with CO2 at 30 psi to reach 0.1 ppm O2. It strikes me as a waste of time and CO2.
Well always removing the head space and replacing it with Nitro or co2 makes sense to me (I always do it) However I have not performed the same experiments. I think that the liquid first purge would be best , but more labor intensive, I feel that if just purging with inert gas like co2 would be sufficient to remove most of the danger of Oxidation. If starsan rinse was my last step of cleaning /purge of a keg it would not add any extra steps and be a good regiment to follow, however it is not- I always flush out the starsan with a gallon or so of soda water pushed with 100 psi of co2 till empty…. then fill in a closed system venting with a spundeling valve for fill. Observations- In your example- The pin-lock kegs with the fixed PRV’s could only be purged (Vented through the gas – “in” tank plug thus leaving a small amount of headspace volume in the keg- everything above the short dip tube) I would suggest to switch to a functioning PRV in the lid to properly vent the headspace.
Nothing to lose. The Co2 off fermentation is free. Why not use it?
I auto siphon the beer into the keg, then purge the headspace. I’ve had good results, even winning some competition ribbons (second and third place spots) bottling from these kegs.
It seems like the non-isomerized hops that you would find plentiful in a New England IPA would lend it self more toward oxidation than hops that are isomerized.
Something that I have done is fill a keg halfway with sanitizer, hook up to co2 (purging 3-4 times to hopefully have as much co2 as possible), then I’ll shake the keg up a bunch. This is to sanitize the keg and also create a whole bunch of suds. I then open the keg and dump upside down into my sanitizer bucket, so kind of locking in the co2 and piles of suds. I then let gravity push the beer from the fermenter to the keg from the bottom of the keg. This pushes out the suds as the beer fills (from the bottom).
This is not ideal as to push out a keg filled with sanitizer and pressure transfer, but I’ve made plenty of hazy IPA’s and have had them in kegs for 2-3 months without issues. Before doing this, I did have issues, so it’s not that I don’t know what oxidized hazy IPA tastes like. Not good at all.
Thanks for summarizing these experiments. I always fill my kegs with Starsan and empty with CO2 for all beers. I also purge the head space of my carboys and store all beer cold. My beer lasts up to 18 months without appreciable difference, although when comparing to a new batch of the same beer a 1 year old beer is noticeable. The issue here is oxygen content, storage temperature, and storage time. The first experiment has the greatest O2 difference and most sensitive beer, so this is expected to have a significant difference. The last two experiments much less difference in O@ concentrations. In the stout the difference is only the head space in the kegs and the second both got purged with CO2. Even storing the German pils for 3 months I am not surprised the tasters did not reach a significant conclusion. Beers with caramel malt and large volumes of hops are the most sensitive to O2 as well. In the future I would stick with the fill and purge versus no purge as this exaggerates the O2 delta.
Cheers,
Jim DUnlap
I have developed a routine of filling my kegs with a starsan solution then using pressure from my active fermentation to purge the kegs. It also helps that I now have a unitank to ferment under pressure with so I can even pressurize the kegs for a complete closed transfer after carbonating in the unitank. This saves money on CO2 and as an added benefit I also reduce my carbon footprint!