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Collaborative study on the isolation of salmonella from artificially contaminated milk powder
Abstract:
The suitability of artificially contaminated milk powder as a substrate for salmonella reference samples and its stability under different storage conditions were studied. The need for a reconstitution step in the standard isolation method for salmonellas from milk powders was also investigated. When milk powder was examined in this way with a reconstitution step, differences in laboratory methods and/or storage times had no significant effect on the results after storage at 4 degrees C. With powder stored at room temperature there was a systematic decrease in the number of samples positive as the storage time increased. It is concluded therefore that milk powder contaminated with salmonellas should be stored at 4 degrees C. Examination of such milk powder with a reconstitution step yielded better results than without it and this step is therefore necessary for improving the reproducibility of the method. No significant differences were encountered between the standard isolation method and that used in the authors' laboratories. The results of this study indicate that milk powder is suitable as basic material for reference samples and that a reconstitution step should be included in the standard salmonella isolation procedure.
Insights
Artificially contaminated milk powder is suitable for salmonella reference samples. Storing samples at 4°C ensures stability, and a reconstitution step improves isolation method reproducibility.
Area of Science:
- Food microbiology
- Analytical chemistry
Background:
- Accurate salmonella detection in food is crucial for public health.
- Standardized methods are needed for reliable reference materials in food safety testing.
Purpose of the Study:
- To evaluate milk powder as a substrate for salmonella reference samples.
- To determine optimal storage conditions for salmonella-spiked milk powder.
- To assess the necessity of a reconstitution step in salmonella isolation from milk powder.
Main Methods:
- Artificially contaminating milk powder with salmonella.
- Storing samples at 4°C and room temperature for varying durations.
- Comparing salmonella isolation results with and without a reconstitution step.
- Analyzing the impact of different laboratory methods and storage times on results.
Main Results:
- Milk powder is a suitable substrate for salmonella reference samples.
- Storage at 4°C maintained sample stability, unlike room temperature storage.
- A reconstitution step significantly improved the reproducibility of salmonella isolation.
- No significant differences were found between standard and authors' laboratory methods.
Conclusions:
- Milk powder is appropriate for use as a salmonella reference material.
- Refrigerated storage (4°C) is essential for maintaining the integrity of salmonella-spiked milk powder.
- Incorporating a reconstitution step is critical for enhancing the reliability of salmonella detection methods in milk powder.