Evaluation of the Sanita-kun Coliforms, a dehydrated medium sheet for coliform detection

Abstract

The Sanita-kun Coliforms consists of a transparent cover film, an adhesive sheet, a layer of nonwoven fabric, and a water-soluble compound film, including a culture medium formula for the detection of coliforms. The medium sheet was validated with 26 food types belonging to 9 food categories (meat, poultry, fish and seafood, fruits and vegetable, dairy, chocolate or bakery, animal feeds, pasta, and miscellaneous) using violet red bile (VRB) agar method in the U.S. Food and Drug Administration's Bacteriological Analytical Manual as a reference according to the AOAC guideline. The medium sheet showed 100% inclusivity and exclusivity. Ruggedness study suggested allowances in the incubation temperature and time as 33-35°C and 24 ± 4 h, respectively. The performance of 3 different lots of the medium sheets was equivalent and suggested no change of the performance at least for 3 years. In the comparative recovery study, many samples (84.6%), which were inoculated with a coliform strain, showed no significant difference between the 2 methods. The linear correlation coefficient (r2) to the VRB agar was calculated as 0.94. In the repeatability study, the average relative standard deviation of total foods was 0.10 in the medium sheet. In the independent study, the medium sheet detected significantly more colonies than VRB plates in the frozen raw milk sample, while there was no significant difference between the 2 methods in raw ground beef sample. Comparative recovery study on foods, inoculated and then frozen, showed the medium sheet detected injured cells with better recovery than VRB agar. The analysts in the independent study wrote that the medium sheet was easy to use and read overall. The Sanita-kun sheet provides an alternative method to coliform count agar.