O 3 and ClO 2 gases are very powerful oxidizing agents and effective against a wide range of microorganisms. Therefore, they attracted attention for the treatment of foods and food contact surfaces. However, due to their very reactive nature they may cause changes in the properties of the materials exposed to these gases. The overall objective of this study was to evaluate the changes in the properties of packaging materials after exposure to O 3 and ClO 2 gases, which will lead to the development of new processing methods and selection of suitable packaging materials for these processes. To achieve this objective mechanical, thermal and barrier properties of plastic films commonly used in food packaging were determined after treatment with O 3 and ClO 2 . In addition, effects of various O 3 and ClO 2 gas treatment methods on quality characteristics of green peppers were investigated.
Changes were observed in two mechanical properties of linear low density polyethylene (LLDPE), low density polyethylene (LDPE), oriented polypropylene (OPP) and biaxially oriented nylon (BON) after O 3 and ClO 2 dioxide treatment. Extent and nature of the change depended on the treatment conditions and the type of the polymer.
While O 3 caused significant changes in the thermal properties of OPP and BON, thermal properties of the same films were not affected from ClO 2 exposure. Melting temperature of both OPP and BON shifted to lower temperatures. A cold crystallization peak was observed for O 3 treated BON.
Permeability of O 3 through LLDPE, OPP and BON was much lower compared to ClO 2 gas. Oxygen permeability of O 3 treated LLDPE and BON decreased considerably with increasing treatment time. ClO 2 also caused a decrease in the oxygen permeability of BON, while a slight increase in the permeability was observed for LLDPE.
Three different gas treatments were applied on green peppers. None of the treatments had any negative effects on the color and the texture of the product. Since ClO 2 treatment before packaging provided the most reduction in microbial population without any negative effect on quality, it was the most effective treatment for green peppers among the methods investigated in this study.
