I cooked a pot of chicken soup. It tastes good 
. I let it sit out for a bit and bacteria grew, I’m sure. I cooked it again. Did the second cooking kill the bacteria? If so, why can’t you just re-cook food that goes bad?
Re-heating will kill bacteria, however while those bacteria were alive they produced toxic waste products which re-heating will not eliminate.
Yup, but also there are some types of bacteria like Bacillus or* Clostridium * that are spore formers. Now if the bacteria are growing and happy in chicken broth they won’t produce spores. they only do this if they’re “challenged” in the environment. Try putting the chicken broth in your window sill. I know you think the sun heating it up will help bacterial growth, but they also hate UV light. The spores will be resistant to boiling to a point, and after the environment becomes hospitipal again they will come out of their spores and begin munching on your soup.
I’m assuming this is not an actual storage suggestion for cooked soup, because if it is, it’s a lousy one. UV from sunlight will not sterlilise a pot of soup.
I didn’t mean to say it would sterilize it… I was just thinking of someway to irritate the bacteria into triggering the steps of turning into a spore. By no means will applying doses of UV light like that produce this effect in mass, just maybe the ones close to reproduction who pull the trigger to past. The OP just mentioned ways of trying to have the soup still somewhat suitable for eating. Which means not waiting until the soup has shriveled into a pile of mold. Only once all the nutrients are sucked out of the soup, and it literally becomes a chemical wasteland will the bacteria all produce spores.
I can’t think of any other way to make spores grow in an aesthetically pleasing bowl of soup that is left “sitting around”.
Not only that, but most of the UV that makes it down to ground level doesn’t even get through the glass in the window. You get some harmless UV-A passing through, but the -B and -C bands are completely blocked.