Relating quality characteristics of aged eggs and fresh eggs to vitelline membrane strength as determined by a texture analyzer.

The TA-XT21 texture analyzer (TA) was used to evaluate vitelline membrane strength (VMS). Fresh and aged (1 wk at 25 C) eggs (n = 48 eggs x 2 replications) were evaluated. Fresh and aged eggs were further divided into two groups of yolk only or whole egg (with intact albumen). Yolk index, Haugh units, pH, broken-out egg weights, VMS, yolk viscosity, and scanning electron microscopy (SEM) images were evaluated. Results from the TA indicated a decrease in VMS in aged eggs compared to fresh eggs and in yolk-only eggs compared to whole eggs. The SEM images indicated a loss of structural integrity in aged eggs as compared to fresh eggs. As expected, aged eggs also had higher albumen and yolk pH, lower Haugh units, lower yolk index, and decreased viscosity compared to fresh eggs. There were no differences in broken-out egg weights or whole egg pH between fresh and aged eggs. As the yolk membrane strength increased, yolk index (r = 0.59) and Haugh units (r = 0.56) decreased, and yolk pH (r = -0.64) and albumen pH (r = -0.57) increased. The study suggests that the TA combined with the modified extrusion cell may be effective in determining VMS. In addition, yolk index, Haugh units, and yolk and albumen pH may be used to predict changes in VMS.