I was just remembering some recalls somewhat recently of big bags of frozen fruit in stores like costco. And i was wondering, how can any bad bacteria survive the freezing long enough to make people sick by the time they buy and eat the fruit? Shouldn’t the freezing process kill practically everything?
In: Biology
Freezing doesn’t generally kill bacteria; it tends to be too small to be affected (unlike parasites and some molds). Instead, freezing just slows down the bacteria. So once it’s thawed, that bad bacteria is free to once again become a problem.
Similar to how you still need to cook a frozen chicken.
No, freezing doesn’t actually kill all microbes, it just stops their reproduction meaning they don’t multiply. But many bacteria can survive in that “cryogenic” state for a long while and then come back to life when they warm up again.
They’re basically so small that as long as the freezing doesn’t make their cells burst, they will survive.
Bacteria and viruses can remain alive in permafrost for hundreds of thousands of years. Heat (high enough) can kill them, freezing doesn’t automatically kill them. (Speaking as a former kitchen/food safety manager).
https://www.abc.net.au/news/2023-05-09/ancient-viruses-climate-change-global-pandemic-risk/102277398
It was contaminated before it was frozen, and just like freezing things doesn’t kill bacteria.
Bacteria are small. So small that their structures aren’t affected by freezing.
Instead, freezing puts bacteria into a state of hibernation – or to sleep. Once it thaws out, it wakes up and continues to do what bacteria do – eat, reproduce and express waste products.
The most common contamination in foods is from E Coli, Listeria or Salmonella.
You’re partly right – freezing kills practically everything – just not these particular bacteria.
Freezing doesn’t kill everything, and even if it did many dangerous bacteria produce toxins which are not destroyed by freezing. If they produced enough toxins before freezing it would make you sick even if the bacteria are dead.
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