Development of pulsed UV light processes for surface fungal disinfection of fresh fruits

Pulsed UV (PUV) power techniques were studied as a nonthermal, residue-free alternative to contact pesticides and to evaluate the surface disinfection of fresh fruits using this type of extremely rapid, high-peak power UV beams. Coherent 248-nm beams from excimer lasers were used to simulate a variety of pulsed light sources now commercially available. Surface disinfection on a series of fresh fruits (i.e., apples, kiwi, lemon, nectarines, oranges, peaches, pears, raspberries, and grapes), representing economically important commodities, were studied and evaluated. Plant (fungal) pathogens were rapidly (<10 s), efficiently (>5 log), and reproducibly killed on fruit surfaces. However, in naturally infected or inoculated (sprayed) fruits, a fraction of the inoculum may penetrate into the epidermis or locate in injured tissue in crevices or in surface irregularities. Under these conditions, only partial disinfection was obtained due to UV shielding (shadowing) effects, which prevent the highly directional, coherent PUV beam from reaching its target. For maximum disinfection efficiency, coherent PUV sources must be combined with dispersing reflectors, and fruits must be handled to ensure uniform exposure to multidirectional incident beams. New, existing, noncoherent, broadband, pulsed light beams (high in UV emission) from arc lamps appear to provide adequate PUV light sources capable of meeting the conditions for commercial applications in slight-modified conveyorized operations. Therefore, PUV techniques may provide effective, commercial-scale, reliable, and viable residue-free alternatives to chemical (contact) pesticides.