Salmonella survival during soft-cooked eggs processing by temperature-controlled water circulator

Abstract

Soft-cooked eggs have been cooked and served worldwide, however concerns frequently raise about the safety of these preparations, assuming the possibility of eggs be contaminated by Salmonella. Temperature-controlled water circulators at low temperature (62 °C–65 °C) for long periods (at least 1 h) has been used to thermally process eggs, aiming to modify its textures. However, time and temperature patterns are not in agreement with some recommendations for processing food preparations at least 70 °C. This study was undertaken to analyze the survival of Salmonella spp. during soft-cooked eggs processing by temperature-controlled water circulator. A pool of Salmonella spp. was inoculated in egg yolks and were incubated at 37 °C, for 18 h, reaching 7.7 ± 0.1 log10 CFU/g. Contaminated eggs were processed at 62 °C for 60 min and samples were collected in order to investigate Salmonella survival. Results indicated that the egg center temperature reached 61.7 ± 0.4 °C after 30 min, completely inactivating 7.7 log of Salmonella spp. After 30 min of cooking, yolk remained liquid and the egg white slightly opaque, demonstrating that the Salmonella inactivation was not related with the solidification of egg white or yolk. The survival curve did not follow first order kinetic and Double Weibull model was used to estimate inactivation kinetic parameters. In summary, the results of this study can be used by food processors in order to validate soft-cooked eggs processing by temperature-controlled water circulator.