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AW: Analysis of Food Irradiation Using TLD
Franz Schoenhofer
PhD, MR iR
Habicherg. 31/7
A-1160 Vienna
AUSTRIA
phone -43-(0)699-1168-1319
Andrew,
The original question was about "TLD and associated methods". While I
still insist that TLD (Thermoluminescence Dosimetry) is no method to
find out about whether something has been irradiated I clearly wrote
that this can be verified by using thermoluminescence, which clearly
makes a difference. During irradiation radicals are formed, which
exhibit thermoluminescence when heated and not recombining for instance
in water containing food. This is not restricted to minerals in spices,
seafood, mushrooms, other food, but is used on any dry material
associated with food like bones in chicken or fish. Your comment on the
possibility of measuring the original dose used for sterilisation is
partly correct: It needs very careful calibration and I do not know
whether the problem of fading - which is a function of time - ever has
been solved. Especially spices may be kept for a relatively long time,
so if the time of irradiation was not known (and which company would
tell you, if they claim that the spices have not been irradiated!) no
determination of the original dose would be possible. With other
foodstuff like lettuce exposed to a too high irradiation dose would
yield an organic slurry. Irradiating deboned meat, muscle or fat tissue
will form certain characteristic fatty acids which can be determined by
gas chromatography. Chemoluminescence has also been used for
determination of irradiation, but thermoluminescence proved to be easier
to handle and more reliable. Starch (like in potatoes or similar
foodstuff will be degraded to a certain extent, so a slurry of minced
food will show a lower viscosity. Certain vitamins like ascorbic acid
will be destroyed in fresh fruits and their depletion can be used for
irradiation detection. Potatoes, onions and similar vegetables or fruits
will not sprout after irradiation (this is what they are irradiated for)
etc. etc. etc.
I have studied the possibility of detecting irradiation of food very
carefully between about 1989 and 1995, even visiting the then leading
laboratory at the research establishment in Muenchen-Neuherberg in
Germany on my own costs and collected tens of kilos of literature. When
I came so far as to establish such a laboratory within the framework of
my work for the Federal Institute for Food Control and Research in my
department another department was assigned the work... (They needed a
laboratory to award to somebody the title of "Head of Department".) So
this is the reason why I still remember quite a lot about this topic and
why I know that it needs a terrible lot of first theoretical and then
practical work to establish a laboratory for the detection of food
irradiation.
Regarding your comment on use on a routine basis I can tell you that
about 1995 the Germans were using thermoluminescence for the detection
of irradiation of spices in a lot of their food quality control network
on a real routine basis and the German authorities conducted a large
number of intercomparison runs for certification of their laboratories.
Though the detection methods seem to be well established now the battle
over "irradiation yes or no" seems to be more or less over. As far as I
know, the USA has lifted its ban for certain food, even the European
Union has allowed certain food to be irradiated, from the viewpoint of
public health the permit for spices is probably the most important one.
Therefore interest in detection of irradiation has much declined.
Finally a funny, but real story: In the late 90's my former institute
received several packages of Turkish frog legs, which were declared as
having been irradiated. The institute found out that they were n o t
irradiated. Though irradiation was then forbidden the import company was
charged because of false declaration!
Best regards,
Franz
I enjoy my retirement, working a lot on radiation protection projects I
am interested in. Hope you do the same. Unfortunately there will hardly
be another Mururoa project.
--------------------------------------------------------------------
> -----Ursprüngliche Nachricht-----
> Von: Andrew McEwan [mailto:acmcewan@clear.net.nz]
> Gesendet: Sonntag, 19. September 2004 06:22
> An: Franz Schönhofer; 'Rotunda, Joseph'; 'RadSafe'
> Cc: 'Liepert, Harold'
> Betreff: Re: Analysis of Food Irradiation Using TLD
>
> Franz
>
> I no longer have the original enquiry to Radsafe on this matter.
However
> I
> would note thermoluminescence has been used to assess doses to some
> foodstuffs such as spices which are irradiated to high (2.5 Mrad, 25
kGy)
> doses to kill bacteria for food safety purposes. Within the spices are
> very
> small quantities of inorganic minerals which can, after careful
> extraction,
> be heated and made to yield a thermoluminescence signal. I am not
aware of
> the technique being used on a routine basis anywhere but it has
certainly
> been investigated as an independent means of determining whether
> foodstuffs
> like spices have been irradiated.
>
> Regards
>
> Andrew McEwan
> ----- Original Message -----
> From: "Franz Schönhofer" <franz.schoenhofer@CHELLO.AT>
> To: "'Rotunda, Joseph'" <joseph.rotunda@thermo.com>; "'RadSafe'"
> <radsafe@list.vanderbilt.edu>
> Cc: "'Liepert, Harold'" <harold.liepert@thermo.com>
> Sent: Saturday, September 18, 2004 9:15 AM
> Subject: AW: Analysis of Food Irradiation Using TLD
>
>
> >
> >
> > Franz Schoenhofer
> > PhD, MR iR
> > Habicherg. 31/7
> > A-1160 Vienna
> > AUSTRIA
> > phone -43-699-1168-1319
> >
> > -------------------------------------------------------------
> >
> >
> > Joe,
> >
> > Your message is really difficult to understand.
> >
> > Do you know, that "TLD" is the abbreviation for "Thermoluminescence
> > Dosimetry", a method to determine the dose to somebody or something
from
> > gamma-radiation, exposing certain material to radiation. You cannot
> > detect food irradiation with that method, unless you expose a
> > TLDosemeter together with the food in order to determine the dose -
> > well, and then you know, that it was irradiated anyway.
> >
> > What are "associated methods"? Could you clarify?
> >
> > Thermoluminescence phenomena can be used to detect irradiation of
food
> > and other material. For various food other methods like
> > gas-chromatography, viscosity or various biological methods might be
> > applicable. There is plenty of literature on that.
> >
> > I recommend that you consult the relevant literature to find out,
what
> > you actually want - your request for "TLD and associated methods"
gives
> > me the impression that you do not know it. Starting the business of
> > finding irradiated food from scratch needs a "little" more than
asking
> > at RADSAFE whether somebody has "experience with Analysis of Food
> > Irradiation using TLD and associated methods", not to talk about
> > becoming an accredited laboratory!
> >
> > Franz
> >
> > --------------------------------------------------------------------
> >
> > > -----Ursprüngliche Nachricht-----
> > > Von: owner-radsafe@list.vanderbilt.edu [mailto:owner-
> > > radsafe@list.vanderbilt.edu] Im Auftrag von Rotunda, Joseph
> > > Gesendet: Donnerstag, 16. September 2004 19:40
> > > An: RadSafe
> > > Cc: Liepert, Harold; Rotunda, Joseph
> > > Betreff: Analysis of Food Irradiation Using TLD
> > >
> > > Does anyone have experience with Analysis of Food Irradiation
Using
> > TLD
> > > and associated methods? If so, would you please respond to my
email
> > > address. Thank you.
> > >
> > > Best Regards,
> > > Joe Rotunda
> > >
> > >
> >
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> >
> >
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