Freshness criteria based on physical and chemical modifications occuring in eggs during aging

The aim of this study was to investigate some physical and chemical modifications that take place in eggs during aging in order to propose objective criteria for judging egg freshness. The proportion of albumen, yolk, thick and thin albumen, pH and the content of Pyroglutamic acid, uridine, glucose and uric acid in both albumen and yolk were investigated during the storage of eggs at different temperatures. Except for glucose and uric acid, all the variables considered changed during storage. Some of these can be considered useful indices of freshness and tentative suggestions for appropriate limits for grade A and A-extra eggs are given. The Limits proposed for grade A eggs are the pH of the albumen less than or equal to 9.4, the thick to thin albumen ratio greater than or equal to 0.4, the concentration of pyroglutamic acid and uridine in albumen less than or equal to 15 ppm and less than or equal to 50 ppm, respectively. A critical discussion of European Union regulations on eggs is also presented