infection tastes. how can you tell?????

[bog69]

we had our 2nd ag tasted by a head brewer from a local micro brewery & he said it had a mild infection. it tasted great when we put into our corny (& the extra into bottles). but 10 days later it has lost its nice hop taste & is very flat but the bottle did pop when it was opened. i couldnt taste anything wrong just that it wasnt very nice. no tcp tastes or anything distinctive. none of our beers have been brilliant but does this mean they all have been infected???

[anomalous_result]

Experience. It's the guy's job. There are various flavours linked to infection, but just because a beer tastes crap doesn't mean it's infected (although I'd take a head brewer's word for it), it might be you don't like the brew, or it could be one of a host of other off-flavours. Palmer's How to Brew seems to be as good a start in this area as any, linked here.