Characterization of slightly acidic electrolyzed water on effective disinfection against microbial safety and retention of phenolic compound in SAEW treated fresh romaine lettuce

This study investigated the effects of processing parameters, specifically the low rate and the combination of diluted HCl and salt (NaCl) at different concentrations, on the properties of the slightly acidic electrolyzed water (SAEW) that was produced. The properties of the SAEW that were analyzed included pH, oxidation-reduction potential (ORP), available chlorine concentrations (ACC), and generated hypochlorous acid (HClO) concentration. NaCl alone resulted in the lowest pH (<4) and the highest ORP values (>1000 mV). Increasing HCl concentrations significantly raised pH levels to greater than 5 and lowered ORP values of SAEW, with the highest pH (5.7) observed with 1.5% HCl and 5% NaCl. The highest HClO concentration of 19.65±1.03 mg/L was obtained with 1.5% HCl:5% NaCl. Interestingly, the concentration of NaCl showed no significant effects on the production of HClO. Furthermore, different concentrations of combined NaCl and HCl significantly influenced the inactivation efficiency on total aerobic bacteria count and changes in phenolic compound content. Increasing HCl concentrations from 0.5% to 2.0% led to an increase in the reduction of aerobic bacteria counts from 2.51 to 4.22 log CFU/g with 5% NaCl and from 2.49 to 3.52 log CFU/g with 10% NaCl. Flow rates significantly contributed to the change in HClO formation and altered the properties of the produced SAEW. Results indicated that SAEW treatment significantly reduced total aerobic bacteria counts. The lower flow rates (0.3 L/min) produced the highest log reductions. Additionally, SAEW treatment led to a reduction in phenolic content, even though considerable amount was retained at lower HClO concentrations. These findings offer valuable information on optimizing SAEW treatment protocols for enhancing microbial safety and extending the shelf life of fresh produce, while considering the impact on the content of phenolic compounds.