This study was undertaken to determine the influence of storage time and temperature on the volume, weight, and pH of egg albumen, the physical strength of vitelline membrane, and the fate of Salmonella Enteritidis artificially inoculated into egg albumen. A fiber-optic probe was used for inoculation with Salmonella Enteritidis at 102, 104, or 106 cells per egg. Both fresh and inoculated eggs were stored at 4, 10, and 22°C for 6 weeks. Five fresh uninoculated eggs from each storage group were collected each week, and the weight, volume, and pH of the egg albumen were measured. The forces, energies, and degrees of membrane deformation required to rupture the vitelline membranes also were determined from either albumen-free yolks or yolks surrounded by albumen. In separate experiments, five inoculated eggs were evaluated each week for populations of Salmonella Enteritidis. When the eggs were stored at 4°C, the albumen retained significantly more volume and weight and had a relatively lower pH. The vitelline membranes from eggs stored at 4 and 10°C required more force and energy for rupture. Salmonellae flourished at 22°C, even in the albumen with the lowest initial population, 102 cells per egg. Storage at 4 and 10°C inhibited the growth of salmonellae in the albumen of eggs with initial populations of 102, 104, or 106 cells per egg. In eggs with initial Salmonella populations of 106 cells per egg that were stored at 22°C, the populations of reached as high as 1010 cells per egg after 4 weeks of storage. Storage at 4 and perhaps 10°C postponed the aging process of chicken eggs, preserved the antimicrobial agents of the albumen, and maintained the integrity of vitelline membrane. Low-temperature storage therefore had a significant impact on the safety and overall quality of the eggs.
Cloning and nucleotide sequence of the gene (citC) encoding a citrate carrier from several Salmonella serovars.