**1. Introduction**

Radiation processing has been used in biotechnological applications for more than 50 years. The effect of radiation on pathogenic microorganisms was first initiated in 1956 by Ethicon Inc. (a

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subsidiary of Johnson and Johnson) together with High Voltage Engineering Corp. (a manu‐ facturer of accelerators) in order to sterilize single-use medical devices such as gloves, hypo‐ dermic needles, sutures, surgical drapes. Nowadays, it is worldwide used, not only for medical devices, but also for cosmetics. The exact mechanism by which radiation kills microorgan‐ isms isnotverywellunderstood,butitis certainlyrelatedto thedamage causedbythe radiation to the DNA molecule of the microorganisms. Also it is generally accepted that the smaller the microorganism the larger the dose of radiation needed to kill it. So, the radiation dose needed to kill bacteria will be larger than the dose needed to kill human cells, and it will be smaller than the dose needed to kill a virus.

Sterilization is not the only area in which radiation can be used in biotechnological applica‐ tions. Radiation is being used to develop new implant materials which are biocompatible. An example of this is the irradiation of water-soluble polymers in aqueous solutions, with or without the addition of another monomer which gives rise to a variety of cross-linked gels which can be used in the biomedical field. Some of these hydrogels can be used to hydrate the skin of patients with severe burns.

Radiation is also used in the area of food preservation. Depending on the dose used on a food commodity, the radiation can either sterilize (e.g., in meat products), kill bacteria including *Salmonella* and *Streptococcus* species, disinfest (e.g., in fruits and grains), kill insects in adult, larvae, or pupae stages, or delay maturation (e.g., in some fruits and vegetables) by decomposing the enzymes responsible for ripening.
