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 s trength (VMS). Fresh and aged (1 wk at 25 C) eggs (n = 48 eggs x 2 replicat ions) were evaluated. Fresh and aged eggs were further divided into two gro ups of yolk only or whole egg (with intact albumen). Yolk index, Haugh unit s, pH, broken-out egg weights, VMS, yolk viscosity, and scanning electron m icroscopy (SEM) images were evaluated. Results from the TA indicated a decr ease in VMS in aged eggs compared to fresh eggs and in yolk-only eggs compa red 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 hig her 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 membra ne strength increased, yolk index (r = 0.59) and Haugh units (r = 0.56) dec reased, and yolk pH (r = -0.64) and albumen pH (r = -0.57) increased. The s tudy suggests that the TA combined with the modified extrusion cell may be effective in determining VMS. In addition, yolk index, Haugh units, and yol k and albumen pH may be used to predict changes in VMS.