Science - March 9, 2010

Salad bar pretty free from harmful bacteria

The salad bar in the Restaurant of the Future of Wageningen UR contains very little harmful bacteria such as E. Coli and salmonella. This is apparent from research carried out by Rikilt and Food & Biobased Research (F&B). Their findings were published last month in the Journal of Food Protection.

The institutes examined the amount of pathogenic bacteria in the 'cold chain'. This chain - in which vegetables are stored, transported and cut - runs from the market gardener to the restaurant. Their aim was to develop a model to predict the food safety aspects of this fresh chain.
Previously, the RIVM had already quantified the presence of E. Coli., salmonella and listeria at the suppliers of the salad greens. In this latest study, Rikilt linked these to growth models of the pathogenic bacteria, while F&B provided a logistic model showing how the vegetables found their way from producers to the restaurant.
In addition, the researchers also took temperature measurements in the refrigerated salad trays in the Restaurant of the Future. 'The salad at the bottom of the tray was nicely cooled, while those on top was often warmer', says researcher Ine van der Fels of Rikilt, the institute for food safety. 'The temperature of the salads rises above 20 degrees Celsius sometimes. In that case, pathogens have free rein to grow.'
Refrigerator
Yet, it's not often that someone falls sick from eating a salad in the restaurant. The researchers extrapolated the results from the Wageningen research restaurant to all salad bars in the Netherlands. If all these were to have the same hygienic practices and refrigeration, each year, 166 salad eaters would fall sick from E. Coli, 187 from salmonella and 0.3 from listeria. 'Listeria is often found in salads, but it's much less potent in making us sick', Van der Fels explains the scores.
The actual contamination figures are higher - annually, 25 thousand people in the Netherlands fall sick due to salmonella in food. As long as vegetables are kept below five degrees Celsius, pathogenic bacteria do not have any chance to grow. 'However, when mistakes occur, such as leaving a fridge door open, food safety problems can arise', says Van der Fels, co-author of the scientific article.

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