Decontamination of Hard-Cooked Eggs by Pulsed UV processing

Abstract. There is a need to reduce the risk of cross contamination in hard cooked egg industry. Therefore, in addition to the packaging Nitrogen 60% and CO₂ 40% and refrigeration storage, decontamination techniques just before the packaging needs to be considered. The aim of this study was to evaluate the effect of pulsed-UV system on hard-cooked eggs and find the optimum conditions for treatment and evaluate the treated eggs during the storage. Response surface design was used to find the optimum distance and time of the Pulsed-UV treatment for hard cooked eggs. To inactivate Escherichia coli K12, coliform, Salmolella Enteritidis, and total bacteria, the optimum distance and time were determined as 8.5 cm and 35 s, respectively. The predicted log reductions for E. coli K12, Coliform, S. Enteritidis, and total bacteria after the Pulsed-UV treatment at optimum condition were 4.6, 3.9, 4.4, and 3.8 log CFU/egg, respectively. The shelf life study was conducted to evaluate the effect of Pulsed-UV treatment at determined optimum conditions on microbiological quality of eggs during six weeks of storage at refrigerated temperature and in a package sealed with 60% Nitrogen and 40% CO₂. The eggs were inoculated with approximately 2 log of E. coli K12 and S. Enteritidis and treated with 35 seconds of Pulsed-UV. During the six weeks of storage, no E. coli K12 and S. Enteritidis growths were observed. The surface temperature changes of the eggs were observed at the optimum distance (8.5 cm) for the Pulsed-UV treatment for various times, which were applied at shelf study. The temperature increased by 10.5^oC by 35 seconds treatment while the temperature was only increased by 1.3^oC by 3 seconds treatment. Moreover, the color changes of the surface of the egg after Pulsed-UV at 8.5 cm for various times and no significant differences were observed. Therefore, it can be concluded that Pulsed-UV treatment was effective for surface sterilization for hard cooked eggs.