Defrosted mince beef -please help

[marshmallowmama]

Defrosted mince beef last night but this morning I have noticed the packet has lots of air in it, I dunno if this means it's offf! We have given it the smell test but can't decide as we are unsure what it's ment to smell like lol what's your thoughts?

Is it in it's original packet? If so, is the plastic top raised up and looking ready to burst?

Does it smell vinegary? It's probably gone over if it does.
It shouldn't really smell of anything.

@Solosunrise yes it's in original packet but has that ready to burst look. I dunno if that has a meaning in itself

@DrHildegardeLanstrom not a vinegar smell but there is a smell (coukd be the way it's ment to smell in fairness as I never normally get up close and personal lol I might just buy another. Was gonna wing it into slow cooker before work but not to worry

The ready to burst look always worries me. Properly off, and you'd know it.
I have notice that if meat is on the turn, the time you notice it is when you start the cooking. I wouldn't put anything in the slow cooker that I had doubts about.
I had savoury mince that I'd left in a the freezer for too long in a plastic freezer bag once. It smelled absolutely foul (plasticky) when it started cooking. I think the bag had started to break down rather than the meat being off, but it got binned anyway.
I hate waste but you don't want to be worrying all day @marshmallowmama

@Solosunrise I'm gonna just buy some new mince on way to work. I don't fancy my chances with it. Thanks so much for your help xx