The goal of this study was to enhance the antimicrobial effect of slightly acidic electrolyzed water (SAEW) through addition of synergistic treatment with ultrasound (US) and mild heat treatment in order to improve the microbial safety of fresh-cut bell pepper. To evaluate the synergistic effects, the Weibull model was used to mathematically measure the effectiveness of the individual and combined treatments against Listeria monocytogenes and Salmonella Typhimurium on the pepper. The combined treatment (SAEWUS60 C) resulted in the TR values of 0.04 and 0.09 min for L. monocytogenes and S. Typhimurium, respectively, as consequence of the minimum value. Subsequently, texture analysis was carried out to test the potential effect on quality of the samples due to the involved mild heat and ultrasound treatment. When compared to the control, there was no significant change (p 0.05) in the texture (color and hardness) of the samples that were treated by 1 min of the combined treatment (SAEWUS60 C) during storage at 4 C for 7 days. This combined treatment achieved approximately 3.0 log CFU/g reduction in the two pathogens. The results demonstrate that the involved hurdle factors which are ultrasound and mild heat achieved the synergistic effect of SAEW against the two pathogens. According to the results of texture analysis, 1 min of SAEWUS60 C is the optimal condition due to without negative influence on the quality of the samples during the storage. The optimal condition shows the enhanced antimicrobial effect of SAEW and enables to improve microbial safety of fresh bell pepper in food industry as a consequence of hurdle approach.
Electrolyzed water generators are readily available in the food industry as a renewable source of hypochlorous acid that eliminates the need for workers to handle hazardous hypochlorite concentrates. We applied electrolyzed water (EW) directly to multi-strain cocktails of Listeria monocytogenes, E. coli O157:H7, and Salmonella sp. at 250 ppm free available chlorine (FAC) and achieved greater than 6-log reductions in 2 min. Lower EW values were examined as antimicrobial interventions for fresh meat (beef carcasses), processed meats (frankfurters), and food contact surfaces (slicing blades). Little or no reduction relative to controls was observed when generic E. coli-inoculated beef carcasses or L. monocytogenes-inoculated frankfurters were showered with EW. Spray application of EW (25 and 250-ppm FAC) onto L. monocytogenes-inoculated slicing blades showed that greater reductions were obtained with clean (3.6 and 5.7-log reduction) vs. dirty (0.6 and 3.3-log reduction) slicing blades, respectively. Trials with L. monocytogenes-inoculated protein-EW solutions demonstrated that protein content as low as 0.1% is capable of eliminating FAC, reducing antimicrobial activity against L. monocytogenes. EW appears better positioned as a surface sanitizer with minimal organic material that can otherwise act as an effective reducing agent to the oxidizing solution rendering it ineffective.
The capacity of slightly acidic hypochlorous acid water (SAHW), in both liquid and spray form, to inactivate bacteria was evaluated as a potential candidate for biosecurity enhancement in poultry production. SAHW (containing 50 or 100 ppm chlorine, pH 6) was able to inactivate Escherichia coli and Salmonella Infantis in liquid to below detectable levels (2.6 log10 CFU/ml) within 5 sec of exposure. In addition, SAHW antibacterial capacity was evaluated by spraying it using a nebulizer into a box containing these bacteria, which were present on the surfaces of glass plates and rayon sheets. SAHW was able to inactivate both bacterial species on the glass plates (dry condition) and rayon sheets within 5 min spraying and 5 min contact times, with the exception of 50 ppm SAHW on the rayon sheets. Furthermore, a corrosivity test determined that SAHW does not corrode metallic objects, even at the longest exposure times (83 days). Our findings demonstrate that SAHW is a good candidate for biosecurity enhancement in the poultry industry. Spraying it on the surfaces of objects, eggshells, egg incubators and transport cages could reduce the chances of contamination and disease transmission. These results augment previous findings demonstrating the competence of SAHW as an anti-viral disinfectant.