Question:
Do the microwaves in a microwave kill bacteria or is it the
heat that kills the bacteria? I am wondering this
because i have a science fair project and i am searching for a
project dealing with bacteria.
Replies:
As far as I'm aware it is the heat that kill
bacteria in a microwave, and they need quite some time
to be dead. The spores that some kind of bacteria make
to survive harsh conditions do not contain much water
and they might survive microwaves. I'm not sure what
bacteria do that can survive high dosis of radiation,
like Deinococcus radiodurans. They can do this by a
very efficient repair system for their DNA. My guess
is that they would also be killed by the heat
generated in a microwave but I haven't found any data
on this.
One word of warning: bacteria that spill food may be
killed in a microwave, but the toxins that they
produce are the actual substances that make us ill,
and they are not destroyed by microwaves. So food that
has gone off is not safe to eat after microwaving.
For your science project on bacteria, have a look at
the Virtual Museum of Bacteria at www.bacteriamuseum.org
Dr. Wassenaar
It's the heat. Microwaves specifically excite molecular rotations; these
do not have any direct effect on the integrity of living systems. However,
the energy in these rotational modes of motion eventually becomes general
heat released to the surroundings; if enough microwave energy is dumped
into a system, it will get hot. Increased temperature does cause
irreversible chemical changes in living systems, abd that is what kills
them.
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