Development of a Novel Egg Surface Decontamination Method via Electro-nano-spray

Chicken eggs and their products are a widely consumed and important source of nutrients for people worldwide. However, they can also be vehicles for pathogens like Salmonella and Escherichia coli (E. coli) that can cause foodborne illnesses. Commercially processed eggs in North America are typically washed with hot water and a chemical solution to decontaminate the surface of eggshells. Although the washing process is effective, this approach also removes the egg cuticle, which acts as a natural barrier to bacterial intrusion. In addition, the use of large amounts of water and washing chemicals produces significant amounts of chemically contaminated wastewater, making this approach environmentally unsustainable. Therefore, exploring alternative methods and innovative technologies that are both effective in preserving food and environmentally friendly would be important to the egg industry. Recently, a new and innovative technique based on nanotechnology called Engineered Water Nanostructures (EWNS) has been developed as a chemical-free solution for disinfection processes. EWNS are formed by electrospraying and ionizing water to create highly charged nanoscale water droplets that possess unique physicochemical properties. It means EWNS are electron-rich water shells that contain a variety of reactive oxygen species (ROS) including hydroxyl radicals, superoxide, and hydrogen peroxide generated during the electrospray process which has been proven to effectively deactivate bacteria. Researchers have explored the effectiveness of EWNS against food-related microorganisms on the surface of various fruits and vegetables. The consumption of eggs is common in Canada, with an average person consuming about 242 eggs per year. However, it has not yet been tested whether EWNS could effectively decontaminate egg surfaces, which could potentially serve as an alternative disinfection method in the egg industry. To evaluate the effectiveness of EWNS on eggshell decontamination, this research project was conducted in three phases. In Phase 1, an electro-nano-spray system was developed to generate EWNS, and lab-based experiments were conducted to assess the effectiveness of the process against E. coli inoculated on the eggshell surface. The parameters investigated included exposure time, water flow rate, and electric field strength to identify the most optimal operating conditions for the EWNS system. In Phase 2, the efficacy of the EWNS method to inactivate Salmonella on the egg surface was investigated under the optimal operating conditions established in Phase 1. In Phase 3, the impact of the EWNS technique on the quality attributes of treated eggs was evaluated and compared to washed and fresh eggs. Egg quality was measured based on physical properties such as eggshell specific gravity, eggshell thickness, albumen and yolk pH, yolk index, Haugh unit, and moisture content of albumen and yolk, as well as chemical components such as the main proteins of albumen. The results of the study showed that in 5 minutes of exposure time, the optimal EWNS operating conditions that produced the highest inactivation efficiency for E. coli inoculated on the egg surface included a water flow rate of 1 μL/min/needle (total flow rate of 16 μL/min), and an electric field strength of 9.0 kV/cm (-4.5 kV at 0.5 cm distance). At these conditions, the system achieved the inactivation efficiency of 97.6% for Escherichia coli W3110 with a 1.64 log reduction and 80.4% for Salmonella enterica serovar Enteritidis with a 0.71 log reduction. Statistical analyses of the physical characteristics of treated eggs showed that there was no significant difference in the properties compared to unwashed and washed eggs one week after treatment (20 eggs per group). Moreover, the physical characteristics of different egg groups (3 eggs per group), including unwashed, washed, and treated eggs, were analyzed over a 21-day storage period, and it was found that the quality of all groups decreased over time. However, there was no significant difference in physical properties between the EWNS-treated eggs and the control (unwashed and washed eggs). The intensity of protein bands of SDS-PAGE gel images were analyzed statistically, and the results indicated that there was no significant variation in protein features between the three sets of eggs (3 eggs per group). The research has demonstrated that the EWNS system can be a promising and environmentally friendly method for decontaminating eggshell surfaces, and may be a suitable substitute for traditional egg sanitation methods. However, the study was limited in scale, and further investigations are required to how the EWNS system can be applied for larger-scale commercial applications.

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