Abstract

Today food manufacturing plants prefer „ready-for-use” liquid egg products to whole eggs. These are easier to use since one should not deal with breaking and storing the egg shell contaminated by faeces. However the shelf life of liquid egg products containing no preservatives is relatively short, there is a need to elaborate new technologies – like the long term (6 to 24 h) heat treatment of liquid egg products on 53 to 55°C. In our measurements we infected non-heat treated liquid egg samples from food industrial plant (liquid egg white, liquid egg yolk, liquid whole egg) with Listeria monocytogenes strain (NCAIM B1371) and incubated at 53 and 55°C. Then dilution plate pouring was performed with Brain Heart Infusion agar for live germ count measurement every 30 min for 6 h and then after 24 h. We observed live germ count reduction of more than 6 orders of magnitude in all liquid egg products even after 6-hour treatment. It was investigated if the new technology can be used to reduce live L. monocytogenes count also in products already heat treated or heat treated and stored in refrigerator. Our results have shown that preliminary pasteurization or pasteurization and storing in refrigerator only slightly increased the thermal resistance of L.  monocytogenes.

Keywords:  Listeria, liquid egg, heat reatment.