An apparatus was designed to deliver low-dose UV-C light to the surface of fruit on a processing line and tested for its control of postharvest decay. It consisted of a row of UV-C emitting lamps mounted on a frame above a conveyer belt that transported the fruit. The dosage of the UV-C light delivered to the fruit surface was regulated by varying the speed of the conveyor belt. Postharvest decay after 28 days storage of `Empire' apples was reduced 52% relative to the untreated checks when the fruit were conveyed at 6.2 m·min−1 (1.38 kJ·m−2 dose) under the UV-C apparatus. Factors affecting the practical application of UV-C irradiation of fruit for controlling postharvest decay are discussed.
C L. Wilson, B. Upchurch, A. El Ghaouth, C. Stevens, V. Khan, S. Droby, and E. Chalutz
J. Liu, C. Stevens, V.A. Khan, J.Y. Lu, C.L. Wilson, O. Adeyeye, M.K. Kabwe, L. Pusey, E. Chalutz, T. Sultana, and S. Droby
The application of low hormetic low-dose ultraviolet light (WV-C, 254 nm) on fruits and vegetables to stimulate beneficial responses is a new method for controlling storage rots and extending the shelf-life of fruits and vegetables. The present study was aimed at treating tomatoes (lycopersicon esculentum) with different UV-C dosages (1.3 to 40 KJ/m2) to induce resistance to black mold (Alternaria alternata), gray mold (Boytris cinerea), and Rhizopus soft rot (Rhizopus stolonifer). Thesediseases were effectively reduced when tomatoes were artificially inoculated following UV-C irradiation UV-C treated tomatoes were firmer in texture and less red in color than the control tomatoes, indicating a delay in ripening. Slower ripening and resistsace to storage rots of tomatoes are probably related. The positive effect of UVC on tomatoes decreased as treatments were performed at stages of increased ripeness.
C. Stevens, V.A. Khan, J.Y. Lu, C.L. Wilson, P.L. Pusey, M.K. Kabwel, Y. Mafolo, J. Liul, E. Chalutz, and S. Droby
Applying low doses of ultraviolet light (254 nm, W-C) reduces the incidence of brown rot of (Monilinia fructicola) peaches, green mold (Penicillium digitatum) of tangerines, and Rhizopus soft rot (Rhizopus stolonifer) of tomatoes and sweetpotatoes resulting from field infection and artificial inoculation. In most studies, applying postharvest fungicide (PF) was better than W-C treatment. In this study, the effectiveness of combining a biocontrol agent, Debaryomyces hansenii (BC), with low UV-C dose for postharvest disease control was investigated. When these commodities were treated with BC 3 days after W-C treatment, the reduction of storage rots was more effective than when UV-C was used alone. For example, the percent brown rot infection of artificially inoculated Elberta peaches 36 hours after inoculation of the nontreated control, peaches treated with UV-C, BC, W-C + BC, and benlate were 100%, 55%, 67%, 12%, and 12%, respectively. The efficacy of W-C + BC was similar to when PF was used alone, indicating that an integration of UV-C treatment and BC can reduce storage rot to the levels of commercial PF treatment.
C. Stevens, C. L. Wilson, J. Y. Lu, V. A. Khan, E. Chalutz, M. K. Kabwe, Z. Haung, S. Droby, and L. Pusey
Low doses of ultraviolet light (254nm UV–C) irradiation reduced postharvest rots of pome, stone and citrus fruits. Brown rot (Monilinia fructicola) of `Elberta' and `Loring' peaches was significantly reduced by UV–C. Alternaria rot (Alternaria spp.) and bitter rot (Colletotrichum spp.) the principal storage rots of `Golden Delicious apples showed significant reduction following UV–C treatment. Further application of UV–C was effective in controlling green mold rot (Penicillium digitatum) of `Dancy' Tangerines and `Marsh Seedless' grapefruits, stem end rot (Alternaria citri), as well as sour rot (Geotrichum candidum) of `Dancy' tangerines after irradiation.
C. Stevens, L. P. Pusey, V.A. Khan, J.Y. Lu, C.L. Wilson, M.A. Wilson, M.K. Kabwe, J. Liu, E. Chaultz, and S. Droby
Flavorcrest, Camden. C. L. Wilson, Loring, Elberta, Summergold and Harken peach varieties were inoculated and naturally infected with Monilinia fructicolo after ultraviolet light irradiation (W-C 254nm) showed increased resistance to brown rot disease. Although dosages ranged from 0 to 20 KJ/m2. 7.5 KJ/m2 was considered the most effective for the peach varieties tested. Pretreatment of peaches by field spraying or dipping into a benomyl fungicide showed no significant differences between non-treated and UV-C treated peaches. However. a combination of a low dose of benomyl (.15g/L) 3 days following UV-C treatment showed a synergistic effect on brown rot reduction when compared to Peaches treated with UV-C alone and a greater reduction of brow rot than benomyl control.