抄録
Foods and foodstuffs must be decontaminated by killing putrefactive and food poisoning microorganisms to maintain wholesomeness. In addition, they must be protected by suitable packaging materials during distribution to the market to prevent microbial contamination from the immediate environment. For this reason it is essential to sterilize packaging materials, too. Sterilizing the containers for aseptic packaging by germicides causes concerns about unwanted persistence and much effort is required for complete removal. Ultraviolet light and ionizing radiation have been utilized to control microorganisms. Of particular interest, electron beams from electron accelerators have higher penetration power than UV, and have already been widely put to practical use in sterilization of medical devices together with Co-60 gamma rays. Radiation sterilization has been expanded to cover packaging materials for aseptic packaging, such as the large capacity thick bag-in-box (BIB) used for liquid food transport, pharmaceutical packaging, such as eye drop containers, plastic caps for PET bottles and containers for beverages, plastic disposable trays and containers for dairy products. The use of irradiation sterilization has grown year after year, for example reaching the economic scale of 20 billion yen in 2007. More recently, low-energy electron beams less than 1 MeV, which have been applied for curing and cross-linking of polymers, have been attracting attention as a means of sterilizing packaging materials because they can be employed without radiation control under the Japanese Act on Prevention of Radiation Disease Due to Radioisotopes. Practical use of low energy electrons for germfree filling of beverages into PET bottles has already started and great expansion can be expected in the future.
