Non-Thermal Processing via Plasma-Activated Sodium Hypochlorite: Inactivation Kinetics and Quality Retention in Fresh-Cut Lettuce.

Plasma-activated water (PAW) represents an innovative disinfection technology utilizing water as the material. In this study, we employed sodium hypochlorite (NaClO; 10 ppm) solution as the substrate for activation by cold plasma (CP) and compared the disinfection efficacy of CP-NaClO with that of NaClO against Escherichia coli, E. coli O157:H7, and Salmonella Typhimurium. In bacterial suspensions, CP-NaClO inactivated all three microorganisms to below the detection limit within 40 s, whereas NaClO treatment resulted in reductions of 5.59, 3.73, and 4.73 log CFU/mL for E. coli, E. coli O157:H7, and S. Typhimurium, respectively. The inactivation kinetics in bacterial suspensions were analyzed using Linear, Weibull, and Log-logistic models, and the Weibull model best described CP-NaClO-mediated inactivation (R2 = 0.95, RMSE = 0.55, AIC = 6.88). CP-NaClO was further employed for disinfecting fresh-cut lettuce. The results indicated that CP-NaClO treatment for 40-70 s achieved a reduction of 0.93-2.76 log CFU/g for the three microorganisms, which was significantly greater than that achieved by NaClO (p < 0.05). No microorganisms were detected in the washing water after 70 s of treatment with CP-NaClO, whereas NaClO wash water contained 1.86 - 2.19 log CFU/mL. CP-NaClO also delayed firmness loss during storage without adversely affecting color attributes. These findings indicated that CP-NaClO was a potential non-thermal processing method, providing a theoretical basis for its application in a fresh-cut industry.