Certainly a piece of my brain knows that I’m not supposed to eat leftovers from my refrigerator after the 3rd or 4th day, certainly not on the 5th or 6th, which I do all the time, and most assuredly not on the 8th day, which I’m alive to tell you, I’ve done.
It’s true the problems with leftovers is listeria, a bacteria that grows in food and strikes hard at pregnant women and their newborns, older adults, and people with weakened immune system. For these groups it can be deadly.
It’s true also, that a human cannot smell listeria. This doesn’t stop me, or many people, from sniffing food to tell if it’s good (i.e. edible) or not.
Milk makes us think we can smell bacteria. What we are smelling in sour milk* is fermenting bacteria. A little fermentation isn’t generally harmful. I do this with my coffee creamer and there have been occasions when I’ll still be pouring out of an “old” container, but if someone comes over, I make them open a new one. I might not always be a food safety practitioner, but I’m a good hostess.
And, I know bad food hurts good people.
But I also hate throwing away food, perhaps over-rationalizing that my scoop of last week’s soup is going to put the landfill over the edge.
So, I sniff. I look for mold. And, for better or worse, I eat.
*Another term for sour milk is “the milk has turned,” which suggests to me someone who took a gulp of sour milk and couldn’t finish speaking the full sentence “the milk has turned sour.” Because they were gagging.