Out of a bit of laziness, I planned to use some Omega Propper Starter to make a quick yeast starter this morning. I opened up the can, which had a little bit of tension to it (not bulging, but definitely under some pressure) and it made a bit of a hiss when opening. Curious, I poured a little into a shot glass -- and it was lightly carbonated! It tasted okay, but had a bit of tartness. I was a bit worried that this might have been fermenting in the can (maybe lacto?), so I dumped the propper and just used DME.
So...is it possible that this was infected? I have used propper once before, and don't recall it being carbonated!