An Independent Evaluation of Two Alternative Rapid Methods for the Detection and Enumeration of Coliforms in Soy Ingredients

Introduction: Coliform bacteria are a commonly used indicator of sanitary quality of foods and water. They are defined as rod-shaped, Gram-negative, non-spore forming, and motile bacteria. Coliforms can be found in the aquatic environment, in soil and on vegetation. They are universally present in large numbers in the feces of warm-blooded animals and thus historically have been used to indicate that other pathogenic organisms of fecal origin may be present.

Purpose: The purpose of the evaluation was to proactively evaluate the performance of the OMA 996.02 method (3M™ High Sensitivity Coliform Count plate) and the AOAC-RI PTM #100401 method (Neogen^®for coliform count) against the FDA BAM Chapter 4 reference method on a variety of soy ingredients: Isolated Soy Protein (ISP), Soy Fiber (SF), Soy Fluid Lecithin (SFL), Soy Deoiled Lecithin (DL), and Soy Nuggets (SN). 

Methods: For each matrix, 5 replicates at three contamination levels (10-100 CFU/g, 100-1,000 CFU/g and 1,000-10,000CFU/g) were evaluated by each method.  Three control replicates were analyzed at 0 CFU/test portion.

Results: The results of the statistical analysis using the difference of means with calculated 95% confidence intervals indicated no statistical difference between the rapid methods and the reference methods in 31 of 36 contamination levels analyzed. The OMA 996.02 produced 2 statistically different levels while the AOAC-RI PTM 100402 method produced 3 statistically significant levels.

Significance: The applicability of OMA 996.02 method (3M™ High Sensitivity Coliform Count plate) covers low levels of coliform bacteria in dairy products, and the applicability of AOAC RI PTM 100401 includes several non-soy matrices, however, the results of these studies indicate both methods perform statistically equivalent to the standard reference method for the five soy ingredients evaluated.  This study supports the fact that the scope of this validation could be expanded.