Effect of Plasma-Activated Water (PAW) on Microbiological and Quality Characteristics of Broccoli and Alfalfa Sprouts

Sprouts have been commonly associated with outbreaks of foodborne illness. Current chlorine-based sanitizers used for decontamination can leave chemical residue. In contrast, plasma-activated water (PAW), can provide an effective decontamination without chemical residue. In this study, we investigated application of PAW on broccoli sprouts and alfalfa sprouts for microbial inactivation. Deionized water was treated with atmospheric pressure plasma jet for 15 minutes (hereafter PAW-15). Inactivation efficacy of PAW-15 was investigated on inoculated E. coli DH5α and aerobic plate counts (APC), in alfalfa sprouts and broccoli sprouts. Chlorine (Cl) (200 ppm) was used as control. PAW-15 was characterized in terms of nitrate and nitrite. Quality changes of sprouts were assessed based on color change (ΔE) and electrolyte leakage (EL). On alfalfa sprouts, PAW-15 was able to reduce E. coli by 2.27 ± 0.38 CFU/gr, which was significantly lower compared to reduction by Cl (6.53 ± 0.37 CFU/gr). On broccoli sprouts, PAW-15 (1.60 ± 0.53 CFU/gr) and Cl (2.02 ± 0.81 CFU/gr) achieved statistically similar reduction in E. coli population. For alfalfa sprouts, PAW-15 reduced APC by 0.91 ± 0.16 CFU/gr, which was similar to Cl (0.81 ± 0.21 CFU/gr). For broccoli sprouts, no significant difference between reduction of APC was observed by PAW-15 (1.37 ± 0.85 CFU/gr) and Cl (1.63 ± 0.99 CFU/gr). Nitrate and nitrite concentrations of PAW-15 were 861.00 ± 67.99 ppm and 90.74 ± 13.14 ppm, respectively. No significant difference was observed on ΔE between Cl and PAW-15 suggesting no visual color difference between PAW-15 and Cl washed sprouts. EL, an indicator of tissue damage, was similar for PAW-15 and Cl washed broccoli sprouts. EL values were low for PAW-15 compared to Cl in treated alfalfa sprouts suggesting less tissue damage due to PAW-15. PAW is a promising alternative to chlorine-based sanitizers for washing sprouts.