Effects of gaseous ozone exposure on cold stored orange fruit

The effect of ozone treatment in relation with storage temperature and venting system on orange fruits decay was examined with intermittent ozone exposure. In order to allow the rooms to be free of gas during the working time the experimental trials were carried out generating ozone in day-night cycles and the ozone concentration in the storage atmosphere was on-line controlled using an infrared analyzer. The effects of gaseous ozone exposure on development of post-harvest green and blue molds {Penicillium digitatum and Penicillium italicum) in artificially inoculated citrus fruit (104 cfu ml"1) were evaluated. Oranges were pre-treated according with the following protocol: control (not washed), washing with ozonized water (0.6 ppm), washing with chlorinated water (50 ppm). After the washing-pre-treatments, fruits were stored for 8 weeks at 5°C and 90-95% relative humidity in an intermittent ozone exposure (treatment) and in normal cold storage room (control). Gaseous ozone at 0.25 ppm did not reduce Penicillium mold incidence in no-wash fruit, apparently the fungal structures in wounds remain protected from the oxidant effect of ozone. The data showed a synergistic effect between ozone or chlorine wash and exposure at 0.25 ppm in inhibiting mycelial growth and preventing sporulation on citrus inoculated with Penicilli. Ozone can also decrease the load of pathogenic spores in the storage room and inhibit the surface growth of mold on packages, walls and floors, with a subsequent reduction in the amount of inoculum available for re-infections of stored product. Ozone exposure reduced ageing and weight loss more than oranges stored in a non-ozonized environment.