Most probable number technique in Escherichia coli count using ISO 16649‐3, ISO 7251, and rapid test enumeration device (TEMPO EC) methods in milk and dairy products

Abstract

AbstractThe aim of the study was to compare of International Standard Organization (ISO) 7251, ISO 16649‐3 most probable number (MPN) assay for the enumeration of Escherichia coli group to the Tempo EC automated method using a variety of spiked milk and milk product foods. Foods evaluated in this study included wet pasta (crema), milk, ayran, and ice cream. The spiked food samples were diluted at three inoculation levels such as low, medium, and high. A comparison of the results indicated that automated system approximated the inoculation level to an automated system. In this study, TEMPO EC, ISO 16649‐3, and ISO 7251 methods are compliant for MPN E. coli count in high, medium, and low contamination level studies. Nevertheless, for precise results, performing primary validation studies by ISO, Association Française de Normalisation (AFNOR), and/or Association Of Official Analytical Chemists (AOAC) will give more reliable results.Practical applicationsIn Turkish Food Codex Microbiological Criteria Communique, it is requested to perform studies of E. coli analysis method in milk and milk products as per ISO 16649‐3. However, in the revised version of ISO 16649‐3, it is stated in the scope of the standard that this method does not provide a full assessment for all products particularly for milk and milk products and that ISO 7251 method should be used in these samples. As it is required in new methods, it has been intended to perform comparative analyses to low, medium, and high inoculation level with rapid the TEMPO EC card and conventional test methods by ISO, AFNOR, and/or AOAC. If the use of TEMPO EC, laboratory response time will improve with automation reducing the time for enumeration of E. coli from 4 days to 24 hr, especially critical for evaluation of perishable foods and outbreak events.