I'm currently experiencing this EXACT problem. My hardware is new, clean, sanitized and my brew tastes good before carb and then after several days of force carb at 20psi 40F, its sour, metallic, and bitter. The Co2 tank is the only thing that's old that I picked up from a local fire shop. I swear it tastes like the inside of the dirty old c02 tank!
Also I'm wondering if this batch is toast now? Or will de-carbing really help?
This is my first post folks. Hello all.
Mike
Not to worry. Your batch is probably just fine.
What you just described sounds very much like carbonic acid bite. Let the keg sit a couple of weeks before tasting it again and you'll find that it's mostly or completely gone. I've had it happen before when burst carbing and it resolved completely given time.
One way to help avoid this is to carb your kegs by chilling the beer to 38-40*F, setting the pressure at 10-12 psi and letting it carb slowly over a two week period.