Twice now I have keeged a beer, force carbonated, and ended up with a wicked lingering aftertaste. Never had an issue prior to this. I clean with PBW and in both cases let the PBW solution sit in the kegs for several days. The second instance I took the entire keg apart, cleaned, sanitized (star san), reassembled and kegged. Force carbonated by cooling keg to 38F, presurizing to 25, shaking for 10-15, returning to kegerator. In both instances I sampled the beer going into the keg and it was really good, just flat and warm. In both instances the flavor was present the very next day; totally undrinkable. If this was a bacterial issue, wouldn't it take more than 12-24 hours to be so prevalent? Advice?
-Bad gas: Refilled cylinder at fire extinguisher place. They used a compressor machine rather than filling from a tank. This concerned me at the time... Better not be just compressed air! I was advised by a local beverage supply co. to use this vendor....
-PBW residue: PBW sat in keg for several days, rinsed with high pressure garden hose
-Gas line contamination....?