Return to the ground floor of this tower
Return to the Main Courtyard
Return to Fort Freedom's home page
]]]]]]]]]]]]]]] FOOD IRRADIATION II [[[[[[[[[[[[[[[[[
By A. Stewart Truswell (9/11/88)
British Medical Journal, 6 June 1987, pp. 1437-8
[Kindly uploaded by Freeman 10602PANC]
Microwave irradiation of food has become accepted as just
another form of cooking. "Food irradiation" is, however, usually
used to mean treatment with waves a million times shorter --
[gamma] rays, x rays, or electron beams. This type of
irradiation cannot be done in the family kitchen; it requires
expensive equipment.
These rays penetrate into a food and produce brief intense
ionisation and consequent changes in the largest molecules,
notably DNA (including that of micro-organisms). Temperature
rises only a little so the food does not look as if it has been
cooked with heat. Low doses of ionising radiations (under 1
kilogray (kGy)) will inhibit sprouting of potatoes and onions,
delay ripening of some fruits, disinfect cereal grains of
insects, and eradicate trichinella in pork. Intermediate doses
(5 to 10 kGy) will extend the shelf life of foods by reducing
microbial loads and eliminate non-sporing pathogens from spices,
chicken, and fish. About 50kGy are needed for bacterial
sterilisation. (The gray is the unit in the Systeme [grave
accent over the first 'e'] International d'Unites [acute accent
over the 'e'] of absorbed energy as radiation passes through
matter and is equal to 1 joule per kg. It has replaced the rad,
with 1 kGy equalling 100 kilorads.)
Irradiated food was used for astronauts. In Britain it is
subject to government control [1] and at present permitted only
for patients who need sterile diets as part of their treatment
[2] and for preparing the rations of experimental animals. The
Joint Expert Committee on Food Irradiation of the Food and
Agriculture Organisation, the International Atomic Energy
Authority, and the World Health Organisation concluded in 1981
that irradiation of food up to an overall dose of 10 kGy is safe
[3], and the Codex Alimentarius Commission has accepted this as a
food standard [4]. Irradiation is now permitted for specific
foods in 30 countries [5], though some of them do not yet have
their own processing plants. Last year the United States Food
and Drug Administration gave permission for irradiation of fresh
fruits and vegetables up to 1 kGy (and spices at higher doses)
[6, 7].
The question of food irradiation is important in all countries
because it may carry a lower risk than some of the various
chemicals currently used, for example, to delay sprouting of
potatoes and onions and to fumigate infested shipments of grain.
Until there is international agreement on labelling, small
amounts of irradiated foods (like spices) may be moving between
countries without indicating their processing history to the
consumer.
In Britain the Advisory Committee on Irradiated and Novel
Foods reported last year and agreed with the international
committee that ionizing irradiation of food up to an overall
average dose of 10 kGy by [gamma] rays or x rays with energies up
to 5 MeV or by electrons with energies up to 10 MeV "presents no
toxicological hazard and introduces no special nutritional or
microbiological problem." With these doses significant
radioactivity cannot be produced in the food. Chemical
compounds, radiolytic products, are formed but only in milligram
amounts or less, and most are not unique -- they occur naturally
before or after conventional processing. Review of toxicological
evidence does not show that irradiated foods are mutagenic, and
laboratory animals fed on irradiated rations have been healthy.
Irradiation does not produce dangerous mutant micro-organisms.
Losses of nutrients are comparable to those from conventional
cooking: vitamin C and thiamine are reduced; vitamin E may be
more affected; and there is insufficient information about
folate. When and if irradiated foods are permitted the British
committee advises mandatory inclusion of "irradiated" in the name
of the food -- "irradiated potatoes" like "pasteurised milk."
When international and several national expert committees
agree with our own committee that a process is safe all that is
usually required is for the government to set limits and define
safe operational procedures. Industry then decides whether it or
the consumer can afford the new process and for which products.
But there is resistance to food irradiation among ordinary
people, who fear (especially after Chernobyl) that the food may
be radioactive. Some professional people have also expressed
anxiety [8-10]. There are four main concerns. Firstly, can we
safely dismiss the few toxicological studies that appeared to
show adverse effects? Discussion focuses [8-10] on a report from
India [11] of increased polyploidy [having more than two sets of
chromosomes] in cultured leucocytes [white blood cells] from four
children with kwashiorkor [a severe protein-deficiency malnutrion
of children] who were given freshly irradiated wheat (but not
others later given stored irradiated wheat). Other scientists in
India [12] and elsewhere think that these experiments were
statistically inadequate, and they have been unable to confirm
them in large numbers of animals and people [13, 14].
The second concern is that irradiation may be used to conceal
bacterial contamination of spoilt food without inactivating
toxins generated by earlier bacterial contamination [10]. But
the same need for good hygiene applies equally to other food
processes like canning and freezing. Thirdly, there could be a
novel pattern of nutrient loss either from the radiation or
because irradiated "fresh" foods may be older when they are
eaten. The British committee conceded that the data on the
effects of irradiation on the nutrient content of foods are not
comprehensive -- but they are more extensive than for many
accepted methods of food processing. The committee recommended
that if irradiation is permitted in Britain the nutrient content
of irradiated food and its consumption pattern should be
monitored. The fourth worry is that we are unable to recognise
that a food has been irradiated. Several laboratories have
searched for substances that would enable an analyst to diagnose
that a food has been irradiated. It is unlikely that any
characteristic substance would be found across all types of foods
after low dose irradiation, but different diagnostic substances
might yet be found in individual foods.
I see no reason why the government should not permit
irradiation of stored winter potatoes and onions at 1 kGy and of
listed spices at moderate dosage. This should be coupled with
registration and control of all irradiation plants and clear
labelling regulations. One problem is that the toxicological
evidence is poorly collected, reviewed, and presented. The World
Health Organisation is planning a publication [5], and I hope
that this -- or perhaps a government publication -- can assemble
the large amount of toxicological work that has been done over
the past 30 years in the International Project in the Field of
Food Irradiation, in the United States, at Leatherhead in
Britain, and in many other Countries.
A Stewart Truswell
Professor of Human Nutrition,
University of Sydney
Wolfson College,
Oxford OX26UD
1 Ministry of Health. Irradiation of Food. London: HMSO, 1964.
(Committee on Medical and Nutritional Aspects of Food
Policy. Report of the working party.)
2 Department of Health and Social Security, Ministry of
Agriculture, Fisheries and Food. Report on the safety and
wholesomeness of irradiated foods by the advisory
committee on irradiated and novel foods. London: HMSO,
1986.
3 Food and Agriculture Organisation, International Atomic
Energy Authority, World Health Organization. Wholesomeness
of irradiated food. Geneva: WHO, 1981. (WHO Technical
Report Series No 659.)
4 Codex Alimentarius Commission. Codex general standard for
irradiated foods and recommended international code of
practice for the operation of radiation facilities used in
the treatment of foods. Vol 15, edition 1. Rome: CAC, 1984.
5 World Health Organisation. Food Irradiation. Geneva: WHO,
1987. (In Point of Fact No. 40.)
6 Kader, AA. Potential applications of ionizing radiation in
postharvest handling of fresh fruits and vegetables. Food
Technology 1986; 40 117-21.
7 United States Department of Health and Human Services, Food
and Drug Administration. Irradiation in the production,
processing and handling of food; final rule. Washington
DC: US Government Printing Office, 1986. (FDA 21: CFR Part
179. Federal Register 18 April: 51 No 75.)
8 Anonymous. More research into safety of irradiated food
urged. [News.] BMA News Review 1987 April: 11.
9 British Medical Association, Board of Science and Education.
Irradiation of foodstuffs. London: BMA, 1987.
10 Webb T, Lang T. Food irradiation: the facts. Wellingborough,
Northants: Thorsons, 1987.
11 Bhaskaram C, Sadasivan G. Effects of feeding irradiated
wheat to malnourished children. Am J Clin Nutr 1975; 28:
130-5.
12 Kesavan PC. Indirect effects of radiation in relation to
food: facts and fallacies. Journal of Nuclear and
Agricultural Biology 1978; 7:93-7.
13 Brynjolfsson A. Wholesomeness of irradiated foods: a review.
Journal of Food Safety 1985; 7:107-26.
14 Food and Agriculture Organization, International Atomic
Energy Authority. Results of feeding trials of irradiated
diets in human volunteers: summary of the Chinese studies.
Rome: FAO, 1986. (Results reported at a seminar for Asia
and the Pacific on the practical application of food
irradiation, Shanghai, People's Republic of China, April
1986.)
* * *
Return to the ground floor of this tower
Return to the Main Courtyard
Return to Fort Freedom's home page