Give it a slight squeeze. If it’s letting air out, you’ll be able to continuously squeeze until liquid comes out. If it is sealed it will resist further squeezing after only a slight squeeze.
Additionally, the seal is under a sealed plastic twist top, which is not actually in the “closed position” at the time of purchase. Hence, you need to break the outer plastic seal (which is itself a tamperproof design) of the cap and twist it closed to break the inner seal to open it initially. If the inner seal was already broken or compromised, even with the cap plastic seal intact, it would simply pour out of the container when you lift it up.
Another precaution is if you see a carton that seems overly full (or inflated), that to me is a sign that the contents have likely spoiled.
Lastly, make your own stock, it’s more flavorful, usually less salt, you get a whole chicken’s meat, and create the best smell in your house. If you would like a recipe, please message in the comments and I’ll add one.
