Evolution of Chemical and Physical Yolk Characteristics during the Storage of Shell Eggs

Yolk modifications during the storage of eggs could influence the quality of yolk products. The aim of this research was to study the rheological behavior and the evolution of some chemical parameters in yolk during the storage of shell eggs at 30, 20, and 5 °C. Water content, pH, furosine, pyroglutamic acid, and uridine increased during storage as a function of temperature. The yolk of fresh eggs showed pseudoplasticity (n = 0.87) with a viscosity decrease from 1.85 to 1.49 Pa·s for an increase in the shear rate from 7.36 to 46.3 s-1. A progressive transition from pseudoplasticity to Newtonity and a decrease in apparent viscosity were observed during storage. The aggregation temperature evaluated by loss modulus and storage modulus measurements rose from 72 °C (fresh eggs) to 80.5 °C (stored eggs). Highly significant correlations between the chemical parameters, especially for the storage at 30 °C, were found; viscosity was highly correlated with dry matter.