Comparison of Water-Assisted Decontamination Systems of Pulsed Light and Ultraviolet for Salmonella Inactivation on Blueberry, Tomato, and Lettuce.

Fresh produce are vulnerable to pathogens during pre- and postharvest stages. Most fresh vegetable and fruits are consumed directly or merely washed with chlorine. We investigated two emerging decontamination technologies, pulse light (PL) and ultraviolet (UV), in combination with washing (referred as water-assisted PL [WPL] and water-assisted UV [WUV]). Blueberries, grape tomatoes, and iceberg lettuce shreds were tested in this study to represent fresh vegetables and fruits with smooth and rough surfaces. Salmonella spp. were used as a model microorganism due to its prevalence in outbreaks. Spot-inoculation and dip-inoculation were used to simulate potential contaminations during irrigation, harvest, transportation, and processing. Two intensity levels of PL (similar to 0.15 and 0.3 J/cm(2) per pulse; 3 pulses/s) and UV (similar to 13 and 28 mW/cm(2)) were tested for 1 and 2 min. For all three types of fresh produce, blueberries, grape tomatoes, and iceberg lettuce shreds, WPL and WUV showed similar Salmonella inactivation effects on fresh produce. For spot-inoculated fresh produce, WPL and WUV treatments reduced 4.5 to 5.7, 4.4 to 5.4, and 1.9 to 3.1 logs of Salmonella on blueberries, tomatoes, and lettuce shreds, respectively. For dip-inoculated fresh produce, WPL and WUV treatments reduced 1.8 to 2.3, 1.9 to 2.5, and 1.9 to 2.6 logs of Salmonella on blueberries, tomatoes, and lettuce shreds, respectively. The majority of the WUV and WPL treatments could eliminate Salmonella in the wash water for blueberries and tomatoes, but not for lettuce. Practical Application Two light systems, pulsed light and UV, for decontamination of fresh produce were evaluated and compared. Results demonstrated that the two systems showed similar decontamination effect on fresh produce, demonstrating that the UV system could be used to replace the pulsed light system to reduce equipment cost.