Source: Book on Plastics for
Food Packaging, presented
by Indian Institute of
Packaging, Mumbai and
published by Indian Centre
for Plastics in the
Environment, Mumbai
Food deteriorate as a result of
physiological changes, activities
of enzymes and attack by insect
pests and micro-organisms during postharvest
storage. Insect infestation and
microbial activity are by far the most
important factors that affect food spoilage.
Among the newly emerging methods
of food preservation, food irradiation
is an effective method to inactivate
micro-organism and destroy insect
pests. Unlike other preservation techniques
that often tend to produce unacceptable
changes in the quality of food,
radiation processing does not bring
about serious organoleptic changes, as
it is a cold process. Extensive studies
have demonstrated that such food are
toxicologically safe and nutritionally
wholesome.
In 1980, a Joint FAO/IAEA/WHO
Expert Committee on the Wholesomeness
of Irradiated Food concluded that
the irradiation of any food commodity
up to an overall average dose of 10 kGy
presents no toxicological hazard and
introduces no special nutritional or microbiological
problems[1]. Since then,
irradiated food has been given access
to markets. In United States, new approvals
for ground beef and fresh fruits
and vegetables were granted[2]. Australia
and New Zealand amended their food
standards for use of irradiation for quarantine
treatment of tropical fruits[3].
Food irradiation has also been approved
in India and a number of commodities
have been cleared under The Prevention
of Food Adulteration Act 1954 rules
(Table 1).
Food irradiation thus offers a proven
and unique option to address the problems
of food security, safety and trade issues.
Food Irradiation
Food irradiation is the use of ionizing
radiation to increase food storage life,
reduce post harvest food losses, and
eliminate food borne pathogens. Ionizing
radiation used in food preservation
include gamma rays, X-rays with energies
of 5 MeV or less and high-energy
electrons of 10 MeV or less. Gamma
rays and X-rays are high-energy (short
wavelength) electromagnetic radiation
consisting of photons of energy transmitted
in the form of wave motion.
Gamma ray source for food processing
applications are the radio-nuclides, cobalt-
60 or caesium-137, while X-rays
are produced by using electron beam
machine. Heating a tungsten element
and accelerating the emitted electrons
inside an evacuated chamber at high
voltage produces high-energy electrons.
Photons and high-energy electrons unlike
other forms of radiation such as
microwave, infrared and ultraviolet radiation
have sufficient energy to cause
ionization of atoms (of low atomic number
e.g. carbon, hydrogen, oxygen),
while passing through a medium containing
them. Ionization is the creation
of positive and negative ions by removal
of orbital electrons from an atom. Formation
of charged ions caused by absorption
of energy of ionizing radiation
in the medium, results in chemical and
biological effects. In the energy ranges
used for food irradiation, both photons
and high-energy electrons produce the
same chemical and biological effects.
The International Commission on
Radiation Units has defined the quantity
of energy absorbed when ionizing radiation
traverses through a medium as ‘the
mean energy imparted to the matter in a
volume element divided by the mass of
the matter in that volume element’. Thus,
the absorbed dose has the units of en-
....contd.
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