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International Journal of Dairy Science

Year: 2021 | Volume: 16 | Issue: 3 | Page No.: 90-97
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Authors

Jianwei Huo

Yan Huang

Raj Rajagopal

Raj Rajagopal

Keywords

Research Article

Loop-Mediated Isothermal Amplification vs. Guobiao Standards Method for Detection of Salmonella in Yoghurt and Yoghurt-Based Drinks

Jianwei Huo, Yan Huang and Raj Rajagopal Raj Rajagopal's LiveDNA
Background and Objective: Salmonella has emerged as an important pathogen in several products beyond traditional poultry products. Salmonella is not considered a risk in fermented foods due to low pH and the presence of probiotic organisms. However, Salmonella can survive in these products and grow given appropriate conditions. It is essential to detect rapidly and accurately contamination of Salmonella in these products. The objective of this study was to optimize growth conditions for Salmonella in yoghurt and yoghurt-based drinks and compare the Loop-mediated Isothermal Amplification (LAMP) assay to the traditional Guobiao standards (GB) 4789.4-2016 method for Salmonella detection. Materials and Methods: Twenty-five grams of different types of yoghurt were inoculated with various levels of Salmonella and enriched in Buffered Peptone Water (BPW) ISO (1:10 and 1:20 dilution) at 41.5°C for 24 hrs. For control, uninoculated samples were enriched similarly. All the samples were analyzed with a Salmonella LAMP-bioluminescent assay and culture-confirmed using GB 4789.4-2016 method. Results: Salmonella failed to grow to detectable levels in yoghurt samples with 1:10 enrichments in BPW ISO even at high levels of artificial contamination (1000 CFU/25 g). The pH was reduced to 4.2-4.3 after enrichment. However, with 1:20 BPW ISO enrichments, Salmonella grew to detectable levels at low spike levels (about 3 CFU/25 g) and was detected by both methods. Conclusion: The alternative LAMP assay enabled reliable and rapid detection of Salmonella in yoghurt and yoghurt-based drinks providing next-day results compared to 3 to 5 days for the GB method.
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