Modelling survival of Salmonella Enteritidis during storage of yoghurt at different temperatures.

The aim of this study was to evaluate the behaviour of Salmonella Enteritidis during the storage of yoghurt at different temperatures (4, 12, 20, and 25 °C), and to develop mathematical models to predict the behaviour of this bacterium as a function of storage temperature. Results indicated that Salmonella was able to survive longer during storage when temperature was low (e.g. 304 h at 4 °C, 60 h at 25 °C). The Geeraerd model with log-decrease and tailing was selected as the most suitable model to describe survival. To evaluate the effect of storage temperature on kinetic parameters such as death rate (kmax) secondary models were developed. The kmax was maximum at 25 °C and minimum at 4 °C with kmax = 0.28 and 0.039 h-1, respectively. The residual population (Nres) ranged 0.5 and 1.8 log CFU/g but there was no temperature dependency of this parameter. A probabilistic example was conduced based on the developed model to assess the exposure to Salmonella by consumption of traditional Turkish yoghurt.

A note on Escherichia coli O157:H7 serotype in Turkish meat products.

255 minced beef, 101 soudjouk and 50 uncooked hamburger samples were analyzed for the presence of Escherichia coli O157:H7 serotype. m-EC and LST broths were used as selective enrichment media and SMAC agar was used as a selective isolation medium. A total of 3 E. coli O157 were isolated by conventional culture techniques; one from each of minced beef, uncooked hamburger and soudjouk but none were identified as the H7 serotype. For determination of selective media-growing cohabitant bacteria, 2645 isolates were obtained from SMAC agar. Results showed that E. coli type 1, Hafnia alvei and Citrobacter freundii were dominant competitive flora. As selective enrichment broth-growing cohabitant microflora existed at higher levels, it was too difficult to isolate E. coli O157 from these mixed flora. Therefore, conventional methods are not suitable for these types of products, because of isolation difficulties and failure to confirm.