Stability Testing of Food Microbiological Proficiency Testing Samples under Simulated Transportation and Room Temperature Conditions

Stability of Food Microbiological Proficiency Testing Samples

Abstract

         This study aimed to evaluate the stability of microbiological proficiency testing samples in food under simulated transport conditions and temperatures. The research was conducted using proficiency testing samples prepared for distribution to laboratory members for the fiscal year 2024. The samples were stored and transported under different conditions: Set 1, where samples were kept at room temperature for 4 days to accelerate degradation due to higher temperatures than normal cold-chain transport, Set 2, simulating transport where the samples were stored at refrigerated temperatures 2–8°C for 3 days and then left at room temperature for 1 day, and Set 3, where samples were kept at refrigerated temperatures 2– 8°C until the final testing day set for members. Results from the qualitative testing of Listeria monocytogenes, Clostridium perfringens, and Salmonella spp. showed stability throughout the storage period. Quantitative test results for Coliforms and Escherichia coli with a threshold of ≤ 0.3σ_pt  which equals ≤ 0.129, it was found that the sample set 1 had a value of 1.569, which was greater than 0.3σ_pt  , indicating that the sample was not stable. Sample sets 2 and 3 had values of 0.121 and 0.087, respectively, which were less than 0.3σ_pt , indicating these samples remained stable. For Staphylococcus aureus, with a threshold of 0.3σ_pt  value of 0.105, the sample sets 1 and 2 had values of 1.087 and 1.090, respectively, which were greater than 0.3σ_pt  indicating decreases in sample stability. However, sample set 3, which was stored under refrigerated conditions of 2–8°C until analysis, had a value of 0.073, which was less than 0.3σ_pt  demonstrating that refrigeration helped maintain sample stability better than room temperature conditions. This study highlights the importance of temperature control during the transportation and storage of proficiency testing samples to ensure the quality and accuracy of analytical results.