Purpose: The purpose of the current study was to evaluate the effectiveness of the combination of two non-thermal technologies (UV and Ultrasound) with different concentrations of chlorine (50 and 200 ppm) on their ability to inactivate four different bacteria such as Escherichia coli, Staphylococcus aureus, Salmonella Enteritidis and Listeria innocua in three products (lettuce, strawberry and cherry tomatoes).
Methods: Commercially available romaine lettuce (Lactuca sativa), strawberries (Fragaria × ananassa) and cherry tomatoes (Solanum lycopersicum var. cerasiforme) were purchased from a local supermarket. Experiments were conducted using four bacterial strains: Escherichia coli NCTC 9001, Staphylococcus aureus NCTC 6571, Salmonella Enteritidis NCTC 6676 and Listeria innocua NCTC 11288. The cocktail of the above microorganisms was inoculated on the three products. The treatment times selected for the non-thermal technologies were varying from 1-30 minutes followed by 3 minutes of NaOCL of two concentrations (50 ppm and 200 ppm). For the microbial analysis, ISO methods were used for the determination of the above microorganisms. A Hunterlab D25 colorimeter was used for color quality measurements.
Results: The results of the present study showed that the combination of US/NaOCL was more effective (more than 3 log reduction) in comparison with UV/NaOCL (2-3 log reduction) for reducing the cocktail of microorganisms in the above food products. Moreover, the color did not change significantly (P < 0.05) when short treatment times were used. Furthermore, differences in disinfection efficiency (P < 0.05) among the food products were obvious.
Significance: These data suggest that the combination of non-thermal with conventional disinfection technologies could find potential applications for decontamination in the food industry.