GAS PLASMA TREATMENTS FOR SUPERFICIAL DECONTAMINATION OF TABLE EGGS

Although eggs are widely used as an inexpensive food of high nutritional value, it is widely recognized that they are one of the main sources of food-borne outbreaks in Europe. Eggshell washing is practised in some countries for reducing bacterial contamination in table eggs, but is not allowed in Europe (except Sweden and the Netherlands). The use of gas plasma offers an original alternative to conventional decontamination techniques of food mainly due to the atmospheric operating temperature, which results in minimal degradation of nutrients, changes in organoleptic properties as well as formation of new potentially dangerous molecules. The main objective of this work was to evaluate the efficacy of cold gas plasma technique in the superficial decontamination of eggshell from the pathogens most frequently associated with eggs. The resistive barrier discharge prototype used to generate cold plasma proved to have a good decontamination power towards Salmonella Enteritidis, Listeria monocytogenes and Escherichia coli deliberately inoculated onto the surface of eggshells giving cell load reductions ranging between 1 and 4 log10 CFU/eggshell depending on the time of treatment, the microbial species and process parameters such as the relative humidity of the chamber during the treatments. Cell inactivation of 1.5-2 log10 CFU/eggshell was observed for total mesophilic bacteria following a 90 minutes exposure to gas plasma. RT-PCR evidenced the presence of viable enterobacteria in 90-min treated eggs although they were not detectable with traditional counting methods. A 90-minutes treatment affected the eggshell color, while no significant differences were detected between the albumen pH of the control and the treated samples.