GROWTH AND SURVIVAL OF E. coli AND S. Typhimurium IN CULTURED BUTTERMILK | ||
| Journal of Food and Dairy Sciences | ||
| Article 9, Volume 32, Issue 7, July 2007, Pages 5455-5464 PDF (508.37 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jfds.2007.204629 | ||
| Author | ||
| Faozia A. A. Ibrahim* | ||
| Dept. of Food Science and Technology, Fac. of Agric., Univ. of Omar El- Mukhtar, El-Beida, Libya. | ||
| Abstract | ||
| This study was carried out to investigate growth and survival patterns of E.coli or S.typhimurium before and after fermentation process of cultured buttermilk product. Emphasis was given to evaluate the effect of level of inoculation, stage of inoculation (pre- or post- fermentation) and the storage temperature on the survival of both bacteria. When E.coli at two levels (6 or 2 logCFU/ml) was inoculated separately into the milk before fermentation, an increase in the bacterial count of 1.5-3 folds was obtained for the two inoculum’s sizes and after 6, 12 hr of fermentation period respectively. The count then declined gradually for each when the fermented milks were stored at 25 or 5oC although the reduction was faster in all cases at 25oC than that at 5oC reaching undetectable levels within 18 and 30 days at two forementioned temperatures respectively for the high inoculum’s size. In contrast, samples with low E.coli inoculum showed a relatively fast disappearance of bacterium as it became undetectable after just 16 and 25 days of storage at 25 and 5oC respectively. A continuous decline was observed when E.coli was inoculated directly into the fermented product stored at two tested temperatures with rapid disappearance at 25oC (16 days) compared with that at low one (5oC) (21days) for high inoculum’s size (6.1 log CFU/ml) whereas lowest survival (3days) was reported with low inoculum size (2.4 log CFU/ml). S.typhimurium showed nearly the same patterns of growth that observed with E.coli when pathogen was inoculated before fermentation. The lowest survival of S.typhimurium was encountered when it was inoculated directly in the fermented products as it disappeared after few days (2 or 3 days) of storage at 25 and 5oC respectively. In light of accumulated evidence, safety and keeping quality of cultured buttermilk were more related to stage of contamination and storage temperatures of final product. | ||
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