Enumeration of Total Aerobic Microorganisms in Foods by SimPlate® Total Plate Count–Color Indicator Methods and Conventional Culture Methods: Collaborative Study

Abstract

The relative efficacy of the SimPlate® Total Plate Count–Color Indicator (TPC–CI) method (SimPlate 35°C) was compared with the AOAC Official Method 966.23 (AOAC 35°C) for enumeration of total aerobic microorganisms in foods. The SimPlate TPC–CI method, incubated at 30°C (SimPlate 30°C), was also compared with the International Organization for Standardization (ISO) 4833 method (ISO 30°C). Six food types were analyzed: ground black pepper, flour, nut meats, frozen hamburger patties, frozen fruits, and fresh vegetables. All foods tested were naturally contaminated. Nineteen laboratories throughout North America and Europe participated in the study. Three method comparisons were conducted. In general, there was <0.3 mean log count difference in recovery among the SimPlate methods and their corresponding reference methods. Mean log counts between the 2 reference methods were also very similar. Repeatability (sr) and reproducibility (sR) standard deviations were similar among the 3 method comparisons. The SimPlate method (35°C) and the AOAC method were comparable for enumerating total aerobic microorganisms in foods. Similarly, the SimPlate method (30°C) was comparable to the ISO method when samples were prepared and incubated according to the ISO method.

COMPARISON OF CONVENTIONAL PLATING AND SIMPLATE METHODS FOR ENUMERATION OF AEROBIC MICROORGANISMS, COLIFORM AND ESCHERICHIA COLI IN FARM ENVIRONMENTAL SAMPLES

“…The APCs of trough TMR and bedding samples from dairy farms were 1.5-2.0 orders of magnitude higher or lower using the SimPlate method. Data obtained in this study with farm and environmental samples are comparable to previous research comparing SimPlate TPC-CI to SMA plating counting in foods (Beuchat et al 1998;Feldsine et al 2003).…”

“…Enumeration of aerobic microorganisms with the SimPlate TPC-CI multiple test medium (BioControl System, Bellevue, WA) method was performed according to the manufacturer's instructions and procedures of Feldsine et al (2003). Sterile water for rehydrating the SimPlate TPC-CI medium contained 1 mL of supplement A per 100 mL.…”

“…One such method, SimPlate, has distinct advantages over conventional plating methodologies. The SimPlate methods require less media preparation and eliminate uncertain counts caused by overcrowding, spreading colonies and interference of particulate matter on plating methods (Feldsine et al 2003). Detection and enumeration of microorganisms by the SimPlate methods rely on a binary detection technology.…”

“…Detection and enumeration of microorganisms by the SimPlate methods rely on a binary detection technology. Visible color changes occur as a result of bacterial enzyme interaction with substrates present in the culture medium Feldsine et al 2003). These biochemical reactions allow for more sensitive enumeration because fewer microorganisms are required to cause the indicator color change than are needed to form a visible colony on agar plates.…”

“…The SimPlate total plate count-color indicator (TPC-CI) is designed for enumeration of aerobic bacterial population in foods and has been approved by the Research Institute of the Association of Analytical Chemists (AOAC), Method 2002.7 (Feldsine et al 2003). The SimPlate coliform and E. coli color indicator (CEc-CI) method is used for detection and quantification of coliforms and E. coli populations in foods.…”