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Publication type: Journal Article
Document type: Full Paper

Year: 2015

Author(s): Gross, S; Johne, A; Adolphs, J; Schlichting, D; Stingl, K; Muller-Graf, C; Braunig, J; Greiner, M; Appel, B; Kasbohrer, A

Title: Salmonella in table eggs from farm to retail - When is cooling required

Source: Food Control. 2015; 47: 254-263.

Authors Vetmeduni Vienna:

Käsbohrer Annemarie

Storage time and temperature are known to be important factors in determining Salmonella growth in table eggs. It is assumed that growth of Salmonella within eggs starts when the egg yolk membrane breaks down, allowing Salmonella to enter and grow. The length of time for which the yolk membrane remains intact is time and temperature dependent. The present study addresses the question whether the current legal requirement in Germany to cool table eggs marketed 18 days after laying needs to be updated. Detailed data on the current storage and transport conditions in Germany were collected. On the basis of these data, typical combinations of temperature and time were selected. For these different time-temperature scenarios, the consequences regarding the probability of growth of Salmonella Enteritidis inside the eggs were calculated. A probabilistic model consisting of nine modules reflecting storage/transport stages from farm to retail in Germany was used to calculate whether the yolk membrane remains intact during the individual steps. Growth of Salmonella was simulated without cooling (room temperature) as well as with two different cooling scenarios (4-6 degrees C and 8-12 degrees C), which are temperature ranges used in Germany by various retailers. Simulations of these scenarios resulted in relative low numbers of eggs with Salmonella growth until purchase (89 out of 50,000 eggs in the uncooled scenario, 10 out of 50,000 eggs stored at 8-12 degrees C and 5 out of 50,000 eggs stored at 4-6 degrees C). These results show that for an average egg trading time of 7.5 days, as was observed for Germany, the probability for the consumer to purchase eggs where no Salmonella growth has started and yolk membrane integrity still exists is high. However, the model supports the necessity for egg cooling after the yolk membrane integrity time is exhausted. Furthermore, the model shows clearly that cooling will extend the time period before the egg yolk membrane breaks down. According to our results, the requirement to cool eggs from the 18th day onwards after laying, as required by legislation in Germany, is reasonable, as it matches the time point of the yolk membrane breakdown for the average egg kept at 18-20 degrees C. Therefore, continuation of this regulation is strongly supported. (C) 2014 Elsevier Ltd. All rights reserved.

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