DETECTION OF Escherichia coli IN DAIRY AND MILK-RELATED PRODUCTS USING DIRECT PLATING AND THE 3-STAGE METHOD | ||||
| Journal of Food and Dairy Sciences | ||||
| Article 10, Volume 2, Issue 8, August 2011, Page 505-512 PDF (420.81 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jfds.2011.81976 | ||||
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| Authors | ||||
| Mona A. Yassin1; M. M. Zin El-Din2; W. M. El-Sharoud1 | ||||
| 1Food Safety and Microbial Physiology Laboratory, Dairy Dept., Fac. Agric., Mans. Univ. | ||||
| 2Faculty of Tourism and Hotels, Mansoura University | ||||
| Abstract | ||||
| Escherichia coli is a frequent foodborne contaminant that negatively affects the quality and safety of dairy products. The present study aimed to examine the presence of E. coli in dairy and milk-related products using two detection methods namely, "direct plating" and "3-stage method". Sixty-nine samples of yoghurt, Domiati cheese, Kariesh cheese, UHT milk, dried skim milk, dried ice-cream, dried whey proteins, creamchantee, infant milk formulas, and "sahlab" were collected from 3 Egyptian governorates and examined for the presence of E. coli. A total of 250 suspected E. coli isolates could be cultured from these samples and subjected to biochemical identification that characterized 35 of these isolates as potential E. coli cultures. Further biochemical testing of these 35 cultures using the Microbact MGNB-12A miniaturized identification system confirmed their belonging to the E. coli species. These isolates were variably recovered from yoghurt (8 isolates), Kariesh cheese (12 isolates), UHT milk (1 isolate), dried ice-cream (2 isolates), creamchantee (1 isolate), infant milk formulas (5 isolates), and sahlab (6 isolates). The 3-stage method showed higher efficiency in detecting E. coli in these products than direct plating. This was attributed to the ability of the 3-stage method to detect injured cells generated on exposure to sub-lethal stress factors including those applied during food manufacture and preservation. The 3-stage method outlined in this study is, therefore, recommended for reliable detection of E. coli in dairy and milk-related products. | ||||
| Keywords | ||||
| Escherichia coli; detection; injured cells; dairy products | ||||
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