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.

Use of pulsed ultraviolet laser light for the cold pasteurization of bovine milk.

Because of concerns that some potentially dangerous microorganisms may survive conventional heat pasteurization of milk and because the heat needed to sterilize milk affects marketability, the ability to efficiently cold pasteurized milk may become more desirable. In this pilot study, we investigated the use of pulsed ultraviolet (PUV) laser light to nonthermally (cold) pasteurized bovine milk. Dairy bulk tank milk was treated with UV light (248 nm) emitted from a pulsed excimer laser. The samples were then analyzed for surviving bacteria by spiral plate counting and subculturing in Trypticase soy broth. Other bulk tank milk samples were inoculated with one of eight relevant milk bacterial species before being exposed to laser light. There was no growth observed for any of the plated or subcultured samples exposed to 25 J/cm2. One bacterial isolate was then used to inoculate milk to further investigate bactericidal laser light doses. Growth was observed for samples treated with an average of 0.3 to 6.6 J/cm2 but not for those treated with 12.6 J/cm2. The results indicate that in principle, the bacterial content of milk can be adequately controlled by exposure to PUV laser light.

Radiation Processing of Foods: An Overview of Scientific Principles and Current Status.

Despite its scientific and technical label of worldwide approval, acceptance and use of food irradiation in the U.S. has become stagnant and a political and psychological issue. As a physical process, food irradiation provides opportunities to improve food protection and preservation technologies. Its use would help solve known public-health problems, as well as minimize the environmental effects caused by chemical and energy-intense processes. In part, this stagnant situation is due to the lack of an educational program, well focused to address critical public concerns and well coordinated by government, academia, and industry. This program should explain the scientific basis and rationale, the advantages, and the limitations of radiation processing of foods. It should also counteract the exploitation by consumer activists who have fostered vocal and seemingly strong opposition. This work provides a summary of educational information and identifies the goals and objectives for consumer education.