SEM (Scanning electron microscopy) assessment of eggshell quality after gas plasma decontamination treatments

Gas plasma treatment of whole egg represents an innovative decontamination technique for the eggshell surface. However, it is not clear if the treatment can damage the natural defence of the egg such as cuticle and shell membranes. Based on previous microbiological tests, 3 batches of 15 extra fresh eggs were treated as follows: gas plasma afterglow for a) 45min or b) 90 min or c) untreated (Control). The plasma emission, produced by a resistive barrier discharge prototype set up by the University of Bologna, was characterized by the presence of very reactive species such as OH and NO radicals. After treatment, the eggs were examined for translucency by hand candling and then empted and rinsed of their content. A 1 cm2 wide strip of eggshell was then carefully removed and subdivided into two smaller sections for assessment of the cuticle and the inner surface of inner shell membrane by SEM (Hitachi 501B, magnification 300×500, 15kV). Our results indicate that there was no significant treatment effects in terms of translucency or in the appearance of the cuticle. The inner surface of the inner shell membrane however displayed a slightly higher incidence of adherent material (albumen) after gas plasma treatment, but this effect could simply be due to ineffective rinsing of the eggshells during the preparation of the samples.