(I am unsure if this is the best place to drop this link - if folks think it belongs on the Food in the News board, I am good with moving it.)
I had a rotten egg last year. Ruined a batch of peanut-butter cookies.
To me air is the enemy. Egs. if we have expired sour cream that’s sealed and never been opened (rare in our kitchen) I’ll open and use it. On the other hand I’ll toss out sour cream that’s been open for a while even if it’s NOT past the expiration date. No science, just me.
The art of fermentation was originally developed as a way to preserve things. If fermented dairy products look good and smell good, they should be fine. When they go off they get moldy or smell off. And if it’s cheese mold, you can often just scrape off the top and what’s underneath is fine, maybe even improved.
I read that pink mold on food is the most dangerous.