No abstract

Since recently, the food industry has been increasingly using ready-to-process egg products as the basic materials instead of shell eggs. Subsequent to breaking shell eggs and completing pasteurisation, they are put on the market as liquid egg products or in powdered form as dried eggs. Consumers prefer liquid eggs which better preserve the advantageous properties of natural eggs, however, their shelf life is short with quick spoilage. We have examined, how long heat treatment is needed at temperatures below pasteurisation to influence the microbiological status of liquid egg products and in this way also their shelf life. A significant difference was found between the microorganism reducing effects of the commonly used pasteurisation process and that of keeping liquid eggs at 55°C for 24 hours. While pasteurisation can only “considerably” reduce the viable cell count in liquid egg products, keeping the product at 55°C for 24 h would very probably result in no or very low viable cell count.

In our experiment whole egg powder samples (infected with Salmonella Enteritidis for microbiological tests) were treated at 50.38-54.62''C for 6.41-24.09 h and tested for decrease in Salmonella count or changes in their solubility and colour Central Composite Rotational Design (CCRD) was used in our tests. In all tests performed within the testing range we achieved a decrease in Salmonella count of at least 5 magnitudes and in cases when the samples were treated at min. 52.5°C for at least 9 h no viable Salmonella could be detected in the whole egg samples at the end of treatments. Our measurements have shown that deterioration of solubility and discolouration was significantly affected only by the temperature change (p<0.05).

Die theoretischen Grundlagen der Kinetik von Fermentationsvorgängen wurden von MONOD [25], NOVICK u. a. [27] bzw. MAXON [23] erarbeitet und später durch HERBERT [6] weiter entwickelt. In den letzten 2 Jahrzehnten publizierten auch sowjetische [16] und tschechoslowakische [21] Forscher auf diesem Gebiet. Unlängst wurden einige grundlegende Mitt. von japanischen Forschern veröffentlicht [17, 18]. In Ungarn beschäftigten sich HOLLÓ u. a. [9–11], NYESTE [28] und NAGY [26] mit der Fermentationskinetik. Die Kinetik der diskontinuierlichen und kontinuierlichen Fermentation wurde bisher hauptsächlich anhand der grundlegenden Gleichungen von MONOD [25] behandelt. Die mathematischen Zusammenhänge sind jedoch — wie schon mehrfach nachgewiesen [5, 7, 8, 12] — nicht allgemein brauchbar, weil die theoretischen und experimentellen Angaben voneinander abweichen. Davon ausgehend möchten wir den Entwicklungsgang der Fermentationskinetik schildern und ihn mit Korrekturen und konkreten Beispielen von verschiedenen Autoren ergänzen1.