Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2004
Publication Date: 12/20/2004
Citation: Palou, L., Smilanick, J.L., Crisosto, C., Mansour, M., Plaza, P. 2004. Ozone gas penetration and control of the sporulation of penicillium digitatum and penicillium italicum within commercial packages of oranges during cold storage. Crop Protection 22:1131-1134. Interpretive Summary: Ozone gas, a common component of polluted air and well-known as a natural barrier to ultraviolet light in the upper atmosphere, also has potent disinfectant activity. We applied ozone gas in a commercial citrus storage and observed that it did inhibit the production of spores by the most important citrus postharvest decay pathogen, the fungus Penicillium digitatum, although the effect was only seen with very open fruit packaging where large vents facilitated penetration of the gas. Inhibition of this pathogen reduced the number of contaminating spores of this pathogen and increases the number of healthy fruit available for sale to consumers.
Technical Abstract: We previously reported that exposure to ozone gas at low doses during cold storage did not control postharvest decay caused by either Penicillium digitatum or P. italicum on wound-inoculated citrus fruit. Aerial mycelial growth and sporulation, however, were inhibited without noticeable ozone phytotoxicity to the fruit. In those trials, contact between fruit and gas was unimpeded. In the present work, ozone gas penetration through packaging materials and effectiveness in controlling sporulation were evaluated on artificially inoculated and commercially packed 'Lanelate' oranges stored at 12.8ºC and exposed to an average ozone concentration of 0.72 ppm (v/v) for 14 days. Inoculated control fruit were stored in a non-ozonated room with the same environmental conditions. Oranges were packed as follows: i) naked in California standard citrus cartons (29.3-L corrugated fiberboard cartons, with lid); ii) naked in vented RPCs (44.7-L returnable plastic containers, without lid); iii) bagged (in transparent low-density polyethylene bags) in RPCs; and iv) bagged in Master cartons (44.6-L corrugated fiberboard cartons, with lid). Ozone levels in the ozonated room and inside the packages were monitored and ozone penetration in each type of package was calculated. Ozone penetration was strongly dependent on the vented area of each type of package, and while it was very low through fiberboard cartons or polyethylene bags (9-17%), it was acceptable through RPCs (82%). Sporulation inhibition of both P. digitatum and P. italicum was clearly related to ozone penetration and it was satisfactory only on oranges packed naked in RPCs. Since the gas was not able to penetrate through fiberboard cartons or plastic bags, which are commonly used in California and worldwide for commercial packaging of not only citrus but a large variety of fruits and vegetables, the suitability of ozone gas exposure during storage as an alternative or complementary treatment for the management of postharvest diseases of fresh produce is limited.