EVOLUTION OF CHEMICAL AND PHYSICAL YOLK CHARACTERISTICS DURING THE STORAGE OF SHELL EGGS

modifications during the storage of eggs could influence the quality o f 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 degrees C. Water content, pH, furosine, pyroglutamic acid, and uridine increased during storage as a function of temperature. The yolk of fresh eggs showed pseudoplas ticity (n = 0.87) with a viscosity decrease from 1.85 to 1.49 Pa . s f or an increase in the shear rate from 7.36 to 46.3 s(-1). A progressiv e transition from pseudoplasticity to Newtonity and a decrease in appa rent viscosity were observed during storage. The aggregation temperatu re evaluated by loss modulus and storage modulus measurements-rose fro m 72 degrees C (fresh eggs) to 80.5 degrees C (stored eggs). Highly si gnificant correlations between the chemical parameters, especially for the storage at 30 degrees C, were found; viscosity was highly correla ted with dry matter.