Document Type : Original Article
Authors
1
Faculty of Agriculture - Benha University
2
Agricultural Microbiology Department, Faculty of Agriculture, Benha University, Egypt.
Abstract
Increasing the shelf life of the product is considered a challenge facing meat product manufacturers, especially products with a short shelf life such as sausage. Therefore, the use of natural agents during processing could have important good health and economic feedback. In this concern, two experiments were designed, the first one was achieved in vitro to study the antibiotics sensitivity ofListeria monocytogenesATCC7644 for sixteen different antibiotics. L. monocytogenes was resistant to five antibiotics belonging to four groups of antibiotics penicillin, cephalosporin, macrolide, and tetracycline. After that, the effect of oils and aqueous, ethanolic and methanolic extracts of three medicinal plants (ginger, lemongrass, thyme) as effective agents for these bacteria to select the more potent as antibacterial agent against L. monocytogenes bacteria in the processed sausage. The results showed that the ethanolic extract of ginger is the most effective in inhibiting the tested bacteria compared to the other extracts .Also, the lowest inhibitory concentration (MIC) of the extract was 5000 mgL-1. In the next experiment, fresh beef sausage was prepared and inoculated withof L. monocytogenes then, treated with MIC of ginger ethanolic extract compared to chemical preservatives (sodium benzoate, sodium nitrate, potassium sorbate, sodium propionate) and kept for 21 days to estimate the periodical changes in the different microbial groups. Total count of aerobic bacteria and coliforms besides the survived L. monocytogenes cells were recorded the obtained data found that all numbers gradually decreased to reach the minimum after 21 days of preservation, In contrast with yeasts and fungi, which increased their number to reach the maximum after 21 days. Moreover, after 21 days the corruptions indicators (pH, thiobarbituric acid (TBA), protein content) in sausage inoculated with L. monocytogenes were estimated. The results showed that there were no significant differences in the pH values between all treatments, moreover, treating sausage with ethanolic ginger extract reduced the TBA and protein content compared to the other treatments.
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