Determination of Performance Characteristics (eLOD50) for Verification of Qualitative Food Microbiological Measurement Methods Based on EN ISO 16140-3:2021

Abstract

Verification of methods for the microbiological examination of foods is vital according to good laboratory practices (GLP) and ISO/IEC 17025. Microbiological reference methods increase the reliability of food quality control laboratory results. This study aimed to verify three qualitative reference methods by calculating the limit of detection at 50% (eLOD50) according to ISO 16140-3 and to address the related challenges for food microbiology laboratories. We determined the eLOD50 for detecting Escherichia coli, Staphylococcus aureus, and Salmonella spp. in different food items. For method implementation verification, the selected food items were fresh cheese Salmonella spp. and pasteurized milk for E. coli and S. aureus. For food item verification, the eLOD50 values of seven other food items (hamburger, black pepper, soybean powder, ultra-high temperature milk, minced meat, whole liquid pasteurized egg, and cake) were also assessed. The eLOD50 values were 0.5 and 1.9 CFU/test portion of pasteurized milk for E. coli and S. aureus, respectively, and 7.5 CFU/test portion in fresh cheese for Salmonella species. All calculated eLOD50 values were compared with acceptance limits. The calculated eLOD50 values of the qualitative methods complied with the acceptance criteria and were approved for all the selected food items.