Inactivation mechanism of Salmonella Typhimurium on the surface of lettuce and physicochemical quality assessment of samples treated by micro-plasma discharged water

The potential of micro-plasma discharged water (m-PDW) treatment on reduction of Salmonella Typhimurium ATCC 14028 from the surface of lettuce leaves was evaluated. The surface of iceberg lettuce and red leaf lettuce pieces (3 cm × 3 cm) was inoculated with a S. Typhimurium suspension. The measured S. Typhimurium reductions were 3.0-log CFU/piece and 2.6-log CFU/piece for iceberg lettuce and red leaf lettuce, respectively for a 3-min treatment. The overall reductions measured for the levels of kaempferol and quercetin in both types of lettuce were within the experimental error for a 3-min plasma treatment. There was no significant change in color (p > 0.05) for plasma operations of the same duration. Leaching of water contributed to a greater extent towards physiochemical changes such as color constraints, kaempferol and quercetin content occurred for the treated lettuce samples, although the overall physicochemical quality changes measured in this study remains in the satisfactory level.