INTRODUCTION

Irradiation of food is a processing and preservation method that produces outcomes comparable to pasteurisation or freezing. The product is exposed to radiation or ionising energy doses during this process. Irradiation increases a product's shelf life at low levels. Insects, mould, bacteria, and other potentially hazardous microorganisms are killed during this process at greater concentrations.

It is permitted to irradiate food using three different forms of ionising radiation.

• The greatest energy of machine-produced electron beams is 10 million electron volts (MeV).

• X-rays produced by mechanical sources have a maximum energy of 5 MeV.

• Co-60 or Ce-137, with corresponding energies of 1.33 and 0.67 MeV, both generate gamma rays.

Forms of radiation

Electron beams

• The streams of extremely rapidly moving electrons created by electron accelerators are known as electron beams. Since they can only pierce a food product an inch and a half deep, electron beams are only used in specific situations for irradiating food.

• Shipping cartons (pre-packaged bulk food items) are not irradiated with electron beams due to poor penetration. Since mechanical sources produce electron beams, they can be turned on and off at will. The operator must be shielded.

Xrays

• X-rays are produced by machine sources, just like electron beams. Since they are photons, Xrays have far better penetration and can pass through food cartons.

• X-rays can also be turned on or off at will. Due to higher penetration, protection is a must.

Gamma rays

• emit gamma rays.

Radioisotopes require shielding because, unlike electron beams and X-rays, they cannot be turned on or off voluntarily and continuously release gamma rays.

• When not in use, the Co-60 source is submerged in water and the lead-shielded Ce-137 source.

Radioisotopes require periodic replenishment because they operate continuously. Since gamma rays consist of photons, they penetrate objects deeply [1].

Units of irradiation

The amount of radiation energy that is absorbed by food as it moves through the radiation field during processing is known as the radiation dose.

"Low" dosages, less than 1 kGy

• Eliminate pests from grains and fruits.

• Prevent tubers from sprouting.

• Postpone the ripening of some fruits and vegetables.

• Eliminate parasites from animal products (such as Trichinella spiralis in pork).

"Medium" dosages between 1 and 10 kGy

• Eliminate E. coli, Salmonella, Shigella, Campylobacter, Yersinia, Listeria, and other pathogens from meat, poultry, and seafood.

• Stop the development of mould on strawberries and other foods.

Higher than 10 kGy "high" dosages

• Kill pests and microbes on spices.

• Commercial sterilisation of food eliminates potentially harmful bacteria. The high dose finds its application in special diets for those with compromised immune systems [2].