I have a package of mushrooms that are still in the package. The sell by date is 12.21. Some of them are a little slimy. Are they still good to use?
Unfortunately, I don't think so. If they're that far past their date and already slimy, I'd probably jettison them....mushrooms can become pretty rank (almost a fetid smell/taste) once they get to that point. For maximum 'shelf life,' best not to buy them in a plastic sealed package, in any case.
In future, don't store in plastic wrap. Transfer them to a paper bag and don't store in a humid veg drawer. Instead of getting slimey and fishy smelling, they will just shrink and can be used longer.
For now, I suppose you can pick thorugh and discard the worst ones. Give it a smell to see if usable. Do not use molded ones.
Yes, the only thing to do at this point is ditch them and get fresh if you can. Slime is never good eats.