Submitted to: Ozone Science and Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 2002
Publication Date: March 1, 2002
Citation: Smilanick, J.L., Margosan, D.M., Mlikota-Gabler, F. Impact of ozonated water on the quality and shelf-life of fresh citrus fruit, stone fruit, and table grapes. Ozone Science and Engineering. 2002. v. 24. p. 343-356. Interpretive Summary: Fungi that rot the fruit are a problem and must be controlled in order to effectively store and market the fruit. Ozone treatment did not control the most troublesome rot fungi on citrus fruit, peaches and nectarines, or table grapes. At very high doses, ozone did partially control rot on peaches and table grapes, but these doses caused injury to the fruit. The brief immersion of these fruit in ozonated water does not appear to be a promising approach to manage rot problems.
Technical Abstract: Spores of fungi that cause postharvest decay of fresh fruit die rapidly in ozonated water. We determined the impact of sporocidal or higher O3 doses on fruit shelf-life & quality. Fruit were placed in stainless steel baskets immersed in 1.5 to 10 ppm O3, dried in air, & examined after storage. O3 concentration did not change during tests. Green mold & sour rot on citrus fruit, caused by Penicillium digitatum & Geotrichum citri aurantii, respectively, were not reduced by 20 min immersion in 10 ppm O3. These fungi infect through wounds; their spores were placed in shallow wounds (1 mm wide x 2 mm deep) 24 hr before treatment. On 5 peach varieties, the average natural incidence of brown rot, caused by Monilinia fructicola, was reduced from 10.9 to 5.4% by 1 min immersion in 1.5 ppm 03. A treatment of 15 min with 5 ppm O3 further reduced decay to 1.7%, but consistent control of brown rot was associated only with this severe treatment & it caused shallow pits on the fruit. Brown rot caused by spores placed in wounds before treatment was rot controlled. Immersion for 1 or 5 min in 5 ppm 03 reduced natural aerobic bacteria populations by 1.1 & 1.6 log 10 units, respectively, & yeast & filamentous fungal populations by 0.7 & 1.3 log 10 units, respectively. Spores of Botrytis cinerea, cause of gray mold, were sprayed on table grape clusters, the clusters were dried, then immersed for 1 to 6 min in 10 ppm O3. In 2 tests, immersion for 1 min in 03 reduced gray mold from 35% among untreated grapes to about 10%, while in 2 other tests, the incidence was only reduced from 35 to 26%. Minor injury to the rachis of Crimson Seedless grapes occurred at high 03 rates. In conclusion, immersion in ozonated water did not control postharvest decay of citrus fruit, injured peaches & nectarines at doses that reliably controlled decay