The viability of Listeria monocytogenes strain Brie-1 was studied in raw and heat-treated (121°C, 15 min) whole eggs, albumen, or yolks during storage at 5 and 20°C. Studies with raw eggs showed that the organism grew only in egg yolks, where initial numbers (106 cells/g) increased to 108 cells/g (generation times of 1.7 d and 2.4 h at 5 and 20°C, respectively). Cell numbers in whole eggs initially declined and then leveled off. A sharp decline in cell numbers was observed in the raw albumen (to 102 cells/g after 22 d at 5°C and to <10 after 55 h at 20°C). In contrast, the organism grew in all heat-treated egg samples. Generation times for cooked whole eggs, yolks, and albumen were 1.9, 2.3, and 2.4 d at 5°C, and 2.6, 2.6, and 3.5 h at 20°C, respectively. The rapid initial decline in populations was observed in raw albumen (pH 8.9), and after adjustments to pH 7.0 or 8.0. Numbers of surviving cells/g after 35 d at 5°C were reduced to 104, 103, and <10, at pH 7, 8, and 9 respectively. With the exception of the raw albumen, refrigerated raw and cooked eggs supported survival and growth of L. monocytogenes, and hence can serve as vehicle of transmission of listeriosis.
Production of Recombinant Chicken IgY-Fc and Evaluation of Its Transport Ability into Avian Egg Yolks
