PRINCIPLES OF FOOD IRRADIATION
Ionising radiation and their sources
According to the Codex General Standard for Irradiated Foods, ionising radiations recommended for use in food processing are:
(I) gamma rays produced from the radioisotopes cobalt-60 (60Co) and cesium-137 (137Cs),and
(II) machinesources generated electron beams (maximum level of 10 MeV) and X-ray (maximum level of 5 MeV).
(I) Gamma rays produced from radioisotopescobalt-60andcesium-137
Cobalt-60 is produced in a nuclear reactor via neutron bombardmentof highly refined cobalt-59 (59Co) pellets, while cesium-137 is produced as a result of uranium fission. Both cobalt-60 and cesium-137 emit highly penetrating gamma rays that can be used to treat food in bulk or in its final packaging.…show more content… The primary reactions include isomerisation and dissociation within molecules and reactions with neighbouring species to produce series of new products including the highly reactive free radicals. Usually the free radicals generated in food on irradiation have a short lifetime. However, in dried or frozen foods containing hard component such as bone, the free radicals will have limited mobility and therefore, persist for a longer period of time.
Another important chemical reaction resulted from ionizing irradiation is water radiolysis. Hydroxylradicals and hydrogen peroxide generated upon the irradiation of water molecules are highly reactive and readily react with most aromatic compounds, carboxylic acids, ketones, aldehydes, and thiols. These chemical changes are important in terms of their effects on the elimination of living food contaminantsin foods. However, undesirable side effects, such as off-flavour, will be inevitable for certain food commodities if conditionof irradiation is not well