> Can someone explain to me how food irradiation is so selective that
> it can disrupt the cellular processes of the microbes that cause
> rotting, with the effect of killing them, but will not disrupt the
> cellular or molecular processes or structure of the food itself?
Rotting is mediated by microorganisms that must reproduce to rot the food.
One of the main effects of ionizing radiation is to cause single-strand
breaks in DNA. The direct and immediate damage is small and localized, and
most of the DNA can function normally. But when the DNA is replicated, as
when a bacterium divides, all hell breaks loose, and large deletions can
occur. This is likely to be lethal to the progeny.
An analogous situation is radiotherapy to kill tumors. Irradiating the
brain is relatively safe because adult nerve cells do not divide, and
radiotherapy is often good for treatment of brain tumors whose cells are
actively dividing. Irradiation of the digestive system or skin is very
harmful because cells in these tissues continue to divide. This is why
anti-cancer treatments make people sick.
> Or is it accepted that irradiation *will* disrupt the cellular or
> molecular processes/structure of the food itself, but that what's bad
> for the "rotting agents" is OK for the nourishing agents?
I don't think they use doses of radiation high enough to kill fruits and
vegetables outright (of course, some food items are not alive when we buy
them anyway). Irradiation of food products can cause chemical changes in
food. Ionizing radiation produces hydroxyl radicals in water. These very
powerful oxidants trigger oxidative chain-reactions that can alter flavor,
and destroy certain vitamins. But such reactions are not unique to ionizing
radiation. Cooking, age, iron, light, and exposure to oxygen cause
oxidative chain reactions. I think it is unfair to make a blanket
condemnation of food irradiation because it can damage vitamins or flavor.
I don't have the data at hand, but the losses may be minor compared to
processes like blanching, canning, or drying.
> I want to know the answer from the
> food-irradiation-proponents' point of view.
I'm not sure I qualify as a proponent. I just don't understand what all the
fuss is about.
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