any any bacteria will be killed of by simmering it for 5 minutes.
indeed, you don't need to keep left over soup / stews in the fridge as long as they are re-boiled daily.
…and cooled quickly...
Microbial food poisoning is caused in 2 different ways; Infection and Intoxication.
Infection is caused by ingestion or the living organism such as Salmonella for example which makes you sick. Such organisms will generallybe killed by sufficient cooking (sporeformers the exception here).
Intoxication is cause by bacteria multiplying in the food and producing toxins as they do so which are released into the food. Most
but not all are destroyed by regular cooking, such Staplococcal and B. cereus (Fried Rice poisoning) toxins.
So, in essence, serious cooking and rapid cooling are the essentials and ensuring that food is never left 'warm' enough for bacteria to multiply. That means from defrosting to cooking as well as from cooked and back to chilled temps.
You can take something from the freezer to begin defrosting at room temp, but after a while (if not frosty on the outside) should be put into either cold water or the fridge such that the outer layers do not reach a nice temperature for microbial growth.
Safest is to cook from frozen where possible.
Next best is in cold water simply because it's far more effective (quicker) than room temperature due to the heat-transfer from the water to the outer surface of the packet.
After cooking, putting the pan into cold water is again a very quick way to cool something before putting it in the freezer. Refresh the water to keep it cold.
So, with good temp control and hygiene you can cook and cool/freeze many times, the food industry does it, and CONTROL is the operative word.