I use isinglass finnings to clear my beer. I have a 1 Litre bottle and use 100ml for 23 litres of beer. When I opened the new bottle and broke the seal is had no smell. 2 weeks later I used it on my next bach and the isinglass had quite a yuck smell to it.
It's now another 2 weeks later and I'm about to use it on another batch and it smells even worse!
The label on the bottle has no use by date or storage instructions.
Does this stuff go off? If it smells bad will it ruin the taste or flavour of the beer?