RADIATION TECHNOLOGY: FOR UPLIFTMENT OF NUTRITIONAL STATUS OF SEA FOODS
1Linga Prabu, D. and 2Kavitha,
1PG Scholar, Division of Fish
Nutrition and biochemistry and Physiology,
Central Institute of Fisheries
Education, Mumbai, India
2UG Scholar, Fisheries
College and Research Institute,
Thoothukudi, Tamilnadu, India.
energy has been used in several fields like agriculture in the form of
radioactive tracers, medicine for radiotherapy and various industries for
different beneficial purposes. One of the most recent and important uses to
which nuclear energy has been successfully applied is the preservation of food
materials like vegetables, fruits, tubers, food grains, meat, fish, etc. Food
irradiation is a process for the treatment of food products to enhance shelf
life and to improve microbial safety. Food Irradiation laboratory of Bhabha
Atomic Research Center (BARC), Govt. of India, Mumbai is one of the Premier
laboratories of such kind in the World. Irradiation technique developed at this
center has been shown to be effective for inhibition of sprouting of potatoes
and onions, delayed ripening of fruits, disinfestations of grains, extension of
shelf life of fish and meat, elimination of pathogens from frozen seafood,
microbial and insect decontamination of spices, etc.
major quality problems with respect to sea foods are their contamination with
microorganisms responsible for spoilage of the food and / or cause food-borne
diseases to the consumers. In addition, insects and parasitic worms encountered
in fish and shellfish also pose quality problems. The leading cause of sea
food-borne illnesses during the last few years was Salmonellosis, followed by Shigellosis
and staphylococcal intoxication. The disease causing organisms include Clostridium
botulinum, Bacillus cereus, Campylobacter jejuni, Escherichia coli, Vibrio
parahaemolyticus, Yersinia enterocolitica and Listeria monocytogenes. The organisms present in fish causes
potential hazards to people who consume fish in raw condition. Several of these
organisms are capable of survive even at refrigerated temperatures, posing
threat to the safety of refrigerated products. Their incidence in processed
fishery products including frozen products has been of great concern in
international trade of the seafood.
appears to be a very suitable method of preservation of these high value food
items. Irradiation not only reduces the total bacterial load on the fishes
treated, but also shows marked selective action against some specific spoilage
organisms, especially Pseudomonas sp. These developments will certainly improve the
availability of good quality perishable foods including sea foods to millions of
people across the country.
SOURCES OF IONIZING RADIATION:
are three main sources of ionizing radiation are gamma rays, electron
accelerators and X-rays.
Gamma rays are electromagnetic
radiation of a very short wave length produced by the spontaneous
disintegration of the atomic nucleus of certain radioactive nuclides i.e.
cobalt — 60, & cesium — 137.
Both are man-made _- rays emitting materials. Cobalt — 60 is most commonly
used. Gamma rays have very high penetrating power and can, therefore, be used
to irradiate bulk items like products in their final shipping container.
Electron accelerators produce high —
energy electron beams and accelerate them to very high speeds producing very high
levels of energy in fractions of a second. Though it is quicker method, the
degree of radiation penetration is poor and hence its application is limited.
X-rays are produced by conversion
from electron beams, but the conversion is not efficient, is uneconomic and hence
not in use now.
is synonymous with pasteurization and is the irradiation process at 1 — 2 KGy
levels for the extension of shelf life of fresh fishery products in ice or
denotes sanitization of frozen products such as shrimp, fillets, and minced
fish blocks, etc. by elimination of pathogenic microorganisms by irradiation at
levels of 2 — 4 KGy.
or radiation sterilization is analogue to thermal processing to achieve
shelf-stability of processed products at ambient temperatures. The treatment
requires exposing food in sealed containers to ionizing radiation at doses
ranging from 25 to 70 KGy to kill all organisms to provide commercial sterility
to the products.
SEAFOOD IRRADIATION IN INDIA:
has found its more proper place in urban areas where economics have shown a
measure of growth and infrastructure. The potential of seafood irradiation as a
means of reducing human suffering and economic losses caused by food-borne
parasitic diseases and bacterial infections are greater in tropical regions. Transportation
of fresh fish to the interior markets of our country poses serious problems.
Application of irradiation process to preserve fresh fish can expand the
marketing areas, stabilize the markets, ensure equitable distribution of the
fishery products, reduce wastage and thus help in economic utilization of sea
foods. According to recent information given by the Marine Products Export
Development Authority, Govt. of India, the location for the country's first
seafood irradiation center has narrowed down to a choice between Bhubaneswar in
Orissa and Vishakhapatnam in Andhra Pradesh. The facility is expected to process
close to Rs. 400 crores of seafood exports every year. The proposed irradiation
plant will have a capacity to process around 10000 tonnes annually, which will
result in irradiation of 2 tonnes of seafood per hour.
a) Fresh Fish:
Fish has a relatively short shelf life due to microbial spoilage, enzyme action
and oxidation. Irradiation at 1-2.5 KGy levels reduces the microbial spoilage and safely extends
the shelf life by several days. Other spoilage mechanisms are unaffected and
fish still lose quality during storage. Both marine and freshwater fish could
be treated successfully. Ideally the fish should be irradiated on board the
b) Frozen fish:
application of irradiation to fish in frozen condition is of special significant
to our frozen fish industry. Pasteurization doses of radiation treatment after
freezing could satisfactorily solve this problem.
c) Canned fish:
treatment could be used as a supplement in the canning processes. A very low
dose of radiation on the canned products after usual autoclaving could ensure
better sterilization of the product without affecting the other qualities.
d) Cured fish:
fish undergo deterioration due to infections by bacteria, fungi and insects,
which get access into them in the course of processing. Irradiation at 0.5 KGy destroys the insects;
Dermestes maculates, Necrobia rufipes and members of family, Sarcophagidae in cured fish, but not
inhibit spoilage due to mold growth.
ROLE OF IRRADIATION IN FISH PRESERVATION:
There are three main areas where
irradiation is helpful in fish preservation. They are; disinfection, extension
of storage life and destruction of pathogens.
It becomes useful in storing dried
fish, by destruction of insects through radiation dose up to 1 KGy. The fish
should store appropriately packed to prevent re-infestation. Parasites can also
be destroyed by low doses radiation.
Extension of storage life:
Employing doses up to 2 KGy, the number
of food spoiling organisms can be significantly reduced, thus resulting in
extension of shelf life.
Destruction of pathogens:
Pathogenic bacteria like Salmonella sp and Listeria sp can be destroyed with radiation
doses between 2 and 5 KGy. These doses are sufficient to destroy only viable
cells; higher doses will necessary to eliminate bacterial spores' even frozen
SAFETY OF IRRADITED SEAFOODS:
regard to the irradiated sea foods, considerations of safety for consumption
involve four aspects; radiological safety, toxicological safety,
microbiological safety and nutritional adequacy.
a) Radiological safety:
Joint FAO/IAEA/WHO Expert Committee on the wholesomeness of irradiated food
(JECFI) has recommended 10 MeV as the maximum permissible energy for electrons,
5 MeV for X-rays and 10 KGy for gamma rays. The measurement showed that no
induced radioactivity could be detected in foods irradiated with 10MeV
electrons at 10 KGy. But, when 20 MeV electrons were used, 0.01 Bq/g was
detected on the day after irradiation. Radioactivity cannot be induced in foods
unless irradiated with radiations above the threshold energy.
b) Toxicological safety:
radiation energy absorbed by irradiated foods causes various chemical reactions
in the food. The chemical reactions induced by >10 KGy dose lead to about
300mg of radiolytic products per kilogram of food. Some are unique to
irradiated foods and of unknown toxicity. Several studies have shown that no
toxicological hazard to human health would arise from consumption of food
irradiated up to an average dose of 10 KGy. No evidence of toxicological
hazards associated with higher doses; however, the recommended dose is up to 10
c) Microbiological safety:
cells are most radiation sensitive, although some bacteria viz. Deinococcus
radiodurans and members
of Moraxella, Actinobacter require comparatively higher doses for their inactivation.
Low (up to 1 KGy) and medium (1-10 KGy) radiation treatments suppress the spoilage
causing gram -ve organisms such as Pseudomonas sp., Proteus sp., Aeromonas
Resistance to irradiation by certain bacteria such as Micrococcus radiodurans and Micrococcus radiophilus has been attributed to their
unusual ability to repair the breaks in DNA caused by irradiation. Studies have
shown that radiation resistance of microorganisms is influenced by treatment
conditions such as temperature, presence of air, nitrogen, vacuum, etc. As
compared to bacteria, viruses require higher radiation doses for their inactivation.
Irradiation process appears little different to other physical processes in its
microbiological changes such as mutation leading to increased resistance,
enhanced pathogenicity of changed physiological traits important to their
identification. In practice, the microbiological risks associated with
irradiation are small.
d) Nutritional adequacy:
nature and extent of the effects of ionizing radiation on nutrients depend on
the composition of food, the radiation dose and modifying factors such as
temperature and presence / absence of oxygen. Irradiation up to 10KGy does not
significantly alter the nutritional value of proteins, carbohydrates, minerals
or saturated fats.
vitro studies have
shown that free amino of proteins are sensitive to radiation. A large
proportion of radiation energy deposited in an irradiated protein leads to
protein denaturation, although it is much less compared with heating.
Structural changes caused by the radiolytic reaction in food proteins may cause
changes in functional properties such as viscosity.
products can cause oxidation of lipids leading to rancidity. Oxidation
reactions can lead to the loss of essential unsaturated fatty acids. Ozone, a
strong oxidizer is produced from oxygen during food irradiation and may oxidize
lipids and also myoglobin resulting in discoloration and flavor changes.
the vitamins, thiamine is more radiation sensitive. Other radiation sensitive
vitamins are A, E, C and K. The loss of vitamins is insignificant below 1 KGy
dosage. However different reports suggest that the vitamin loss caused by
irradiation appears to be contradictory.
Irradiation causes only marginal
changes in flavor, texture, and odor of fish. In fatty fishes, the free
radicals produced as a result of irradiation can initiate autoxidation chain
that will lead to rancidity. The radiation — included flavor changes, described
as 'metallic', 'burnt feather — like', 'rubbery' etc. are associated with
irradiated fish even when the dosage low. Some other organoleptic changes
associated with sterilizing doses are brown discoloration, toughening of texture
and strong bitter flavors develop in fish. Some fat — based pigments get
bleached during irradiation. Integrating
packaging under vacuum with irradiation can suppress bacterial spoilage and
Packaging of irradiated fish:
Flexible packages have special
advantages and many plastic materials can be used in conjunction with
irradiated foods. Ionising radiation may also be used to improve the properties
of polymeric packaging materials and inactivate any micro organisms, with the
packing material might have been contaminated with prior to bringing into
contact with the food. In contact with food, extractives from the package
should not contaminate the food. The packaging material does not get itself
irradiated and induce radioactivity in the food contained.
LEGAL ASPECTS AND PUBLIC HEALTH:
all over the world have the responsibility to control irradiation processing of
food. The International Consultative Group on Food Irradiation (ICGFI) which
was established by the International Organizations such as WHO, FAO, IAEA, has
issued guidelines for preparing regulations to control food irradiation facilities.
Any new method of preservation has necessarily to ensure that no toxic
substances are produced due to the process and the foods preserved by such
methods should not exhibit deleterious effects of any sort on the health of the
consumer. Doubts about risk of induced radioactivity in such foods have been
expressed at times. No report of formation of harmful toxic substances is
available, even though peroxides are formed to some extend in fatty foods
during irradiation. No evidence of development of carcinogenicity in such foods
has yet been put forth. The irradiation processing has to be used only as a
supplement and should never form substitute for good hygienic practices because
it depends upon the initial quality of the raw material.
that have been irradiated must be labeled with green international logo to
inform that the food has been processed by ionizing radiation. The words
"Treated with radiation" or "Treated by irradiation" must be in the same print
style as the product name and be no smaller than one-third the size of the
largest letter in product name.
it can be concluded that exposure of fishery products to ionizing radiation
could effectively eliminate or reduce the pathogens of public health
significance, spoilage causing microorganisms, insects and parasites while
maintaining wholesomeness and sensory quality of the seafood. Such technology
is more useful for the countries like India to meet the nutritional demands of
huge population, as fish is a cheap animal protein source with high essential
amino acids as well as with health beneficial omega — 3 polyunsaturated fatty
K.K. (2001). Post harvest technology of fish and fish products, Daya Publishing
House, Delhi, Pp 440.
(1989). Radiation preservation of fish and fishery products, Technical Report
Series No.303, FAO, Rome.
E.S. and Peterson, M.S. 1982. Preservation of food by ionizing
Radiation, vol. 1, CRC Press, Inc. Florida Pp 378.
T.G., 1976. Physics in food irradiation facilities presented at 1st.
Cong. Eng. Food,
J.T.P.E.E., Lockhart, B.E., Proctor and Licciavdello, J.J., 1954. Ionizing
Radiation for control of fish spoilage, Food Technol, 8:32.
N.W., (Ed.), 1959. Preservation of food with Ionizing Radiations. In the
technology of food preservation. The Avi publishing Company Inc, Westport,
A.S. and Rathnakumar, K., 2008. Fish Processing Technology and product
Development, Narendra publishing House. Delhi. Pp 562.