Quality Assessment of Commercial Eggs: Effects of Oil Coating, Storage Time and Temperature on Physico-Chemical and Microbiological Characteristics

In this study, the qualities of 240 eggs of the medium category, purchased from a local supermarket, were evaluated. The eggs were divided into 4 groups of 60 eggs each. Two groups of eggs were kept at room temperature, while the other two groups were kept in the refrigerator. From these groups, one group of eggs was treated with vegetable oil. The qualities of the eggs were investigated on the first day and then on the 7th, 14th and 21st day. The physicochemical qualities were evaluated by determining rate of weight loss, yolk index, Haugh Index, pH of egg white and yolk, color of the eggshell and egg white/yolk, while the microbiological ones by determining total germ count, fecal streptococci, Salmonella, coliform bacteria and E. coli. Statistical evaluation of obtained results was performed using an analysis of variance (ANOVA) and a principal component analysis. Results indicated that eggs stored at room temperature had a faster quality decline compared with those refrigerated. Applying vegetable oil to eggs before storage can maintain their freshness over time.