Earlier quoted context omitted.
It is. We can it in mason jars at home. The fat floats to the top and solidifies, so even if the seal on the (sterilised!) jar is imperfect, the fat preserves the broth by preventing microbe incursion. Also helps to make it good and salty, and concentrate it down until it just begins (while boiling hot) to be viscous. When cool, it’s thick and gloopy. So long as everything is good and hot when you seal, you’re good.…
> So long as everything is good and hot when you seal, you’re good. Good, maybe. Safe, no. Chicken stock is not acidic enough even for water-bath canning – it must be pressure-canned. Anything else is a risk of botulism.
Tl;dr your canned food can get a fungus that eats the vinegar, reducing the acidity, and allowing botulinum to grow.