Temperature sequence of eggs from oviposition through distribution: production--part 1

During Egg Safety Action Plan hearings in Washington, DC, many questions were raised concerning the egg temperature (T) used in the risk assessment model. Therefore, a national study was initiated to determine the T of eggs from oviposition through distribution. In part 1; researchers gathered data on internal and surface egg T from commercial egg production facilities. An infrared thermometer was used to rapidly measure surface T, and internal T was determined by probing individual eggs. The main effects were geographic region (state) and season evaluated in a factorial design. Egg T data were recorded in the production facilities in standardized comparisons. Regression analysis (P < 0.0001) showed that the R(2) (0.952) between infrared egg surface T and internal T was very high, and validated further use of the infrared thermometer. Hen house egg surface and internal T were significantly influenced by state, season, and the state x season interaction. Mean hen house egg surface T was 27.3 and 23.8 degrees C for summer and winter, respectively, with 29.2 and 26.2 degrees C for egg internal T (P < 0.0001). Hen house eggs from California had the lowest surface and internal T in winter among all the states (P < 0.0001), whereas the highest egg surface T were recorded during summer in North Carolina, Georgia, and Texas, and the highest internal T were recorded from Texas and Georgia. Cooling of warm eggs following oviposition was significantly influenced by season, state, and their interaction. Egg internal T when 3/4 cool was higher in summer vs. winter and higher in North Carolina and Pennsylvania compared with Iowa. The time required to 3/4 cool eggs was greater in winter than summer and greater in Iowa than in other states. These findings showed seasonal and state impacts on ambient T in the hen house that ultimately influenced egg surface and internal T. More important, they showed opportunities to influence cooling rate to improve internal and microbial egg quality.