This study aimed to evaluate the potential of fluorescence spectroscopy at excitation/emission (Ex/Em) wavelengths of 280/354 nm for monitoring plasma-activated water (PAW) disinfection efficacy in vegetable wash water. Vegetable wash water was prepared from cabbage, carrot, and onion, and cabbage wash water (CWW) was further prepared at varying chemical oxygen demand (COD) levels and with bicarbonate. The wash waters were treated with PAW and monitored at 5-minute intervals for changes in fluorescence intensity and physicochemical properties. The relationship between the decrease in fluorescence intensity and the reduction in survival of Salmonella enterica ( S. enterica ) and Listeria monocytogenes ( L. monocytogenes ) following PAW treatment was assessed in CWW, for both wash water reconditioning, and dynamic washing scenarios. Fluorescence intensity strongly correlated with the survival of S. enterica (r = 0.94) and L. monocytogenes (r = 0.96), whereas UV 254(f) and ORP showed moderate correlations. During wash water reconditioning, L. monocytogenes was undetected after 25 min in the 0 and 0.5 mM bicarbonate CWW at fluorescence intensities below 3500 CPS/mA. S. enterica required 30 min for 3 log reduction. During dynamic washing, fluorescence decreased to 833 ± 721 CPS/mA after the first 1-minute cycle, with 2.5 ± 0.8 and 4.1 ± 1.2 log reductions of S. enterica and L. monocytogenes , respectively. Fluorescence intensities below 1800 CPS/mA corresponded with greater than 3 log reduction of L. monocytogenes within 1 min. These results suggest that fluorescence measurements at Ex/Em 280/354 nm are a promising tool for real-time monitoring of PAW disinfection efficacy during wash water reconditioning and dynamic washing. • Fluorescence intensity decreases over plasma-activated water (PAW) treatment time at constant organic load. • Fluorescence decrease strongly correlates with reductions in Salmonella enterica and Listeria monocytogenes . • Fluorescence indicates pathogen survival during wash water reconditioning and dynamic washing. • Fluorescence reflects PAW disinfection efficacy during wash water reconditioning and dynamic washing.
Gongora et al. (Fri,) studied this question.