Off flavors kegging?

[HighVoltageMan!]

Just curious. Did you purge the kegs after sealing them up? Also I have read that CO2 tanks can be contaminated with small amounts of Oxygen, maybe try a different vendor.

There are different grades of CO2. Beverage grade is 99.9% pure, welding CO2 is about 99.5% pure. The rest is impurities, mostly water vapor, ammonia, and of coarse, oxygen. The level of oxygen is about .5 ppm in beverage grade. So if you used 5-6 ounces of CO2 to carbonated your 5 gallons of beer you would be putting about .0000032 ounces of oxygen into the 640 ounces (5 gallons) of beer. Which would give you roughly 5 ppb of dissolved oxygen added from carbonating. Well within the limits. If you carbonated with welding CO2, you could assume 5 times that amount, 25 ppb. Both are within the acceptable levels, but the beverage grade is obviously better.

 

[HashSlinger]

There are different grades of CO2. Beverage grade is 99.9% pure, welding CO2 is about 99.5% pure. The rest is impurities, mostly water vapor, ammonia, and of coarse, oxygen. The level of oxygen is about .5 ppm in beverage grade. So if you used 5-6 ounces of CO2 to carbonated your 5 gallons of beer you would be putting about .0000032 ounces of oxygen into the 640 ounces (5 gallons) of beer. Which would give you roughly 5 ppb of dissolved oxygen added from carbonating. Well within the limits. If you carbonated with welding CO2, you could assume 5 times that amount, 25 ppb. Both are within the acceptable levels, but the beverage grade is obviously better.

I have been buying CO2 from a welding shop which is substantially cheaper than AirGas. So I assume it's welding grade. My IPA's still taste fresh after 6-9 months in the keg. My lawnmower beer starts to show mild oxidation after 3 months. Maybe I should switch to beverage grade.