EFFECTIVENESS OF FAR-UVC 222 NM ON ESCHERICHIA COLI O157:H7 AND LISTERIA MONOCYTOGENES ACROSS DIFFERENT FRESH PRODUCE SURFACES

Abstract

The objective of this study was to evaluate bactericidal activity of far-ultraviolet C (far-UVC) light at 222 nm against Escherichia coli O157:H7 and Listeria monocytogenes on fresh produce with different surface types and characteristics, romaine lettuce and strawberries. Inoculated samples were treated with increasing far-UVC doses (0–210 mJ/cm²) using a krypton-chlorine excimer lamp. Microbial inactivation was measured as a log CFU/g reduction and surface roughness of each sample was determined by 3D optical profilometry. Far-UVC treatment produced larger reductions on romaine lettuce (2.47 log CFU/g for E. coli; 2.33 log CFU/g for L. monocytogenes) compared to strawberries (1.30 and 1.49 log CFU/g), which was anticipated based on romaine lettuce having a smoother surface (Sa: 3.568 µm) compared to a more rugged strawberry surface (Sa: 36.722 µm). Microbial inactivation showed to be influenced by surface properties. Far-UVC exposures did not significantly affect the CIELAB color parameters taken before and after treatment, which suggested minimal harm to the produce as far as visual quality is concerned. This research contributes to the knowledge about the practical role and usefulness of 222 nm far-UVC to improve microbial safety on fresh produce, while allowing for visual as well as marketable appearance of products without chemical or thermal treatment.