FOOD IRRADIATION

[don@radpro.uchicago.edu]

I apologize in advance if the following duplicates some of the 
comment on food irradiation, but I've got 800 email messages to plow 
through and have been unable to follow the thread completely.  Also,
apologies for most misspellings.  

The May 1994 issue of _Food Technology_ contains several articles 
on food irradiation.  On article on "The Wholesomeness if Irradiated foods"
by Donald W. Thayer (p 132 ) contains the following:

"There are questions about other irradiated products that need to be  
addressed, ,in particular the potential loss of vitamin C from fruit
or vegetables irradtiated for insect control.  The issue is complicated 
because fruits and vegetables are living tissue.  Ascorbic acid is a 
sensitive redox compound.  Even at doses below 1 kGy, such as those 
approved for insect control, some ascorbic acid will be converted to its
oxidized dehydro form (Romani, et al. 1963).  Dehydroascorbic acid,
however, is fully as active as the reduced form of the vitamin.
Unfortunately, many of the studies in the literature did not use assay
methods that would detect the oxidized form of the vitamin and thus 
reported erroneously high losses.  During  storage of irradiated potatoes, 
much of the dehydro form is converted back to the reduced form.  However,
in selected products, some loss appears to be irreversible, especially at 
radiation doses > 1 kGy (Thayer et al., 1991).  These losses do not 
appear to be significant at doses intended to control insects in fruits
(<1 kGy) and are lower than those from freezing (Beyers and Thomas, 1979)"

References mentioned:

Beyers, M and Thomas AC, 1979
     Irradiation of subtropical fruits. 4. Changes in certain nutrients
     present in mangoes, papayas, and litchis during canning, freezing,
     and [gamma] irradiation.  J. Agric. Food Chem.  27:48


Romani, RJ, Van Kooy, J, Lim, L, and Bowers, B, 1963
     Radiation physiology of fruit - Ascorbic acid, sulfhydryl and 
     soluble nitrogen content of irradiated citrus.  Radiat. Biol. 3:58

Thayer, DW, Fox, JB Jr, and Lakritz, L, 1991
     Effects of ionizing radiation on vitamins.  Chapt. 11 in 
     "Food Irradiation" ed. S. Thorne, p 285, Elsevier Applied Science
     Publishers, London

I would be happy to fax the article to anyone who requires it, but 
it may take several months for me to get through my email.  My apologies
to Mssrs. Gabbard & Zapantis for late replies to earlier queries -  I'm 
really still working on them.

 

___________________________________________________________________

Don Jordan                          Tel. (312) 702-6299
Office of Radiation Safety          Fax        702-4008
The University of Chicago           email: don@radpro.uchicago.edu
1101 East 57th Street, Room 11
Chicago, Illinois  60637  
                -- Any opinions are the author's --