Stench is such a fascinating concept.
The human brain and olfactory receptors have developed a whole system that says "Do not eat poop," by programming in a code that says "If it smells like poop, you will not like it" and "If it smells like poop and you put it to your nose, you WILL gag, we WILL trigger a vomit reaction, do not smell or consume poop," and because of that, we invented deodorant and have to wash our socks.
Also, certain bacteria and microbes decided "If we put this smell all over this dairy, it will smell bad, and humans will not eat it", which works for us, too, because we then don't drink milk filled with bacteria.
Unless the bacteria eats the milk in a particular way, at which point the human nose goes "Oh, wait! That milk is all stinky! And blue! And isn't milk, but some soft, crumbly substance! Let's eat it and taste that FUNK! I love milk that's been buried underground and devoured by microorganisms for months!"
