Purpose: The purpose of this evaluation was to compare the new method in comparison to the reference methods, VRB agar with MUG overlay and alternatively AOAC 996.02, using solid dairy extracts, irrigation water, and environmental surface sponges.
Methods: Heavy cream (35 % fat) was co-inoculated at five concentrations with Enterobacter and E. coli and split into 5 replicates. Samples were sent to 5 laboratories and tested in duplicate by the new and reference methods, VRBA/MUG overlay and AOAC 996.02 at 32°C for 24 h. Ice cream, egg nog, condensed milk, and container rinses were inoculated similarly and tested in one laboratory. Irrigation water and environmental sponge samples (ISO 18593) were inoculated at 3 bacterial levels split into 5 samples and tested in duplicate at 35°C for 24 h.
Results: Results were evaluated for repeatability (Sr) and by paired-t-test for statistical difference, > 0.5 log. The Peel Plate EC HV results were not significantly different from reference methods in detecting total coliform in the dairy solids at 32°C and in distinguishing E.coli from coliform at 35°C in the water and environmental samples. Production of indicator colors is not consistent in all dairy products at 32°C, so while heavy cream and condensed milk detected E.coli and results were not significantly different from reference method, eggnog and ice cream did not produce the distinguishing colors.
Significance: Peel Plate EC HV demonstrates detection < 1 CFU/5ml with comparable reference method detection of total coliform at 32°C in dairy solids and E. coli/coliform detection to water and surface sponges at 35°C.