IRRADIATION-A
NEW TECHNIQUE OF FOOD PRESERVATION
P.G.Patil
Food is vital for human existence. Conservation
and preservation of food is a prerequisite for food security as
it provides economic stability and self-reliance to a nation.
The need to preserve food has been felt by mankind since time
immemorial.
The seasonal nature of production, long distances
between production and consumption centers and the rising gap
between demand and supply have made this need even more relevant
today. The hot and humid climate prevailing in a country like
India is quite favourable to the growth of numerous insects and
micro-organisms that destroy stored crops and spoile food. Spoilage
can also occur due to chemical and physiological changes in stored
foods. Seafoods, meat and poultry may carry harmful microbes and
parasitic organisms that cause illnesses associated with their
consumption.
As in other parts of the world, India has
also practised various methods of food preservation such as sun
drying, pickling and fermentation which were supplemented with
more energy consuming techniques such as refrigeration, freezing
and canning .Each of these methods has its merits and demerits.
Man has always been in search of newer methods to preserve foods
with least change in sensory qualities. Food irradiation is one
of the latest methods developed for this purpose.
Food irradiation involves exposure of food
to short wave energy to achieve a specific purpose such as extension
in shelf-life, insect disinfestations and elimination of food-borne
pathogens and parasites.Compared to heat or chemical treatment,
irradiation is considered a more effective and appropriate technology
to destroy food-borne pathogens. It offers a number of advantages
to producers processors, retailers and consumers.
Food irradiation is the controlled application
of energy from ionizing radiations such as gamma rays, electrons
and X-rays for food preservation. Gamma rays and X-rays are short
wavelength radiations of the electromagnetic spectrum which includes
radiowaves, microwaves and infrared, visible and ultraviolet light.
Gamma rays are emitted by radioisotopes such as Cobalt-60 and
Caesium-137 while electrons and X-rays are generated by machines
using electricity.
Working
Irradiation works by disrupting the biological
processes that lead to decay. In their interaction with water
and other molecules that make up food and living organisms, radiation
energy is absorbed by the molecules they contact. The reactions
with the DNA cause the death of micro-organisms and insects and
impair the ability of potatoes and onions to sprout.
Today, some 38 countries worldwide including
India have approved the use of irradiation for over 100 food items
and about 30 of these are applying the technology on a limited
commercial scale. South Africa has cleared more than 40 food items.
Process
Food irradiation is carried out inside an
irradiation chamber shielded by 1.5-1.8 metre thick concrete walls.
Food either pre-packed or placed in bulk in suitable containers
is sent into the irradiation chamber with the help of an automatic
conveyor. The conveyor goes through a concrete wall labyrinth
which prevents radiation from reaching the work area and operator
room. When the facility is not in use the radiation source is
stored under 6 metre deep water. The water shield does not allow
radiation to escape into the irradiation chamber, thus permitting
free access to personnel to carry out plant maintenance. For treating
food the source is brought to the irradiation position above the
water level after activation of all safety devices. The goods
in aluminium carriers or boxes are mechanically positioned around
the source rack and are turned round their own axis, so that the
contents are irradiated on both the sides.
Advantages
Irradiation is a cold process and can be
used to pasteurize and sterilize foods without damaging freshness
and texture of food.Unlike chemical fumigants, irradiation does
not leave any harmful toxic residues in food and is more effective.
It is efficient and can be used to treat prepacked commodities.
Food can be irradiated in a food irradiation
plant which is authorized by the Atomic Energy Regulatory Board
and licensed by the competent authority. The licence to carry
out food irradiation operation is given only after ascertaining
the safety of the installation, its suitability to ensure proper
process control, and availability of licenced operators and qualified
staff. A facility could be put up as a private, public or joint
sector company.
The volume and number of irradiated food
products entering trade has grown steadily in recent years, particularly
in China, Belgium, France, The Netherlands,SouthAfrica and the
United States.
Status
In 1994 the Government of India approved
irradiation of onion, potato and spices for internal marketing
and consumption. At present theDepartment of Atomic Energy has
two facilities for food irradiation. There is one commercial irradiation
facility for medical products in Mumbai which can also be used
for the treatment of spices. The other one is a small pilot scale
food package irradiator at Food Technology Division, Bhabha Atomic
Research Centre, Mumbai, which can treat up to 500 kg of onion
and potato per hour.
Irradiated food cannot be recognized by sight,
smell, taste or touch all packages of irradiated foods to be marketed
in India are labelled with the words "Processed by irradiation
method", and the date of irradiation, licence number of the
facility and the purpose of irradiation . Consumers have a free
choice to buy irradiated or non-irradiated commodity.
