food irradiation stuff (radiation biology lesson?) - reply

[Louis Iselin <liselin@intprop.com>]

>>Charles Migliore (Chasmig@aol.com) wrote:

>>The question expressed concern about "living" food, fruits and
veggies. How is
>>it that radiation alters bacteria and parasites to the point of  death
but
>>does not significantly affect the living veggies?  A complete carrot
plant can
>>be grown from a single cell.

   We need a better understanding of what is meant by "living food".
   Most RadSafers consider a cut plant to be dead.  We realized that
   a new plant may still be viable from the dead one, but the processes
   that we associate with a living plant soon stop.

>>How can you say that radiation kills bacteria but does not affect the
food "in
>>so many words", without it sounding like an article of faith? Why
doesnt the
>>DNA damage to the bacteria also damage the DNA of the food? I guess
the hard
>>part is explaining why damaged veggie DNA doesnt matter. I suppose it
would
>>account for the slight loss of vitamins.

   Radiation does affect the food.  The effect is small, though, on the
order
   of pasteurization or cooking.  Others have already pointed out that
radiation
   effects are greater on rapidly dividing cells.  The plant's cells are
no
   longer in this state, while the bacteria we wish to kill are still
active.

   Another way to look at this question is to ask where is the DNA in
each
   case?  In a single-celled organism, the target DNA is right with the
   rest of the whole organism.  Either we kill the organism or not.  In
a
   plant, the DNA is present in each cell, but since the plant is a
multi-
   cellular organism, the plant cells are specialized.  Damage to the
DNA
   of any given cell in a harvested carrot is really of no consequence.
   The carrot is no longer growing.  Also, the DNA of the carrot has
   nothing/little(?) to do with the nutrition of the carrot.

   (Is there a daily Recommended Dietary Allowance for DNA? Whose?)


>Martin_Haas@notes.ymp.gov wrote:

>There may be a potential fly in the ointment /food with the current
round
>of explanations.  This has to do with the germination potential of
seeds
>within food.  If the food radiation levels are sufficient to kill
bacteria,
>and higher organisms, won't it also kill whatever germ cells are in
seeds
>that may accompany fruit.  To the public, the inability of seeds to
>germinate may constitute some form of death to the food in question.
The
>logical explanation for this of course is that this is not dissimilar
to
>the effects of heating.

#Peter Fear (fearp@VAX.CS.HSCSYR.EDU) wrote:

#If you are going to plant the potatoes (or other vegies) that you buy
from
#the store, then they will not grow if they have been irradiated. But if
#they have been irradiated, you will be able to eat then before they
spoil
#or sprout.


   The ability of various seeds to germinate after irradiation has
   been studied since the 1950s by various groups.  As has been noted
   on RadSafe in the past, many plants, like wheat, have a higher
   germination rate and higher yields after irradiation to various
doses.
   The cause of this effect is uncertain.  It has been suggested that
   bacteria are eliminated which damage the seedling as it starts to
   grow, thus giving the seedling a head start on life, so to speak.

   It sounds like we (RadSafers) need to remember the dose and the
target
   in our food irradiation discussions.  Irradiated foods will still
spoil.
   Irradiated foodstuffs may still sprout.  Spoilage is slower, since
the
   "germ" population has been drastically reduced.  Take irradiated
fruit,
   especially strawberries as an example.  I've eaten them.  They will
last
   about a week in the refrigerator, compared to maybe two days
otherwise.
   That's a storage increase of over 200% just by irradiating.

   As a final comment, some people will want to eat "natural" produce.
   Their best hope is to grow it themselves.  If you want raw produce
that
   has as little processing as possible, grow it yourself.

   Louis
   (Personal opinions only, all work-related standard disclaimers
apply.)
   

Louis H. Iselin, Ph.D.
work:  liselin@intprop.com
home: lhi@poboxes.com