Читать книгу Analytical Food Microbiology - Ahmed E. Yousef - Страница 40

The replicate organism direct agar contact (RODAC) method may be used on easily accessible flat surfaces. In this method, Petri plates are filled with an agar medium suitable for the microbiota to be analyzed. These plates may be prepared in the laboratory or purchased from a commercial source. The RODAC plates should contain enough agar medium so that the surface of the medium is convex and rises above the rim of the plate. At the sampling site, the agar medium in the RODAC plate is exposed to the surface being sampled. This exposure is accomplished by pressing the plate against the sampled surface and rolling the plate while applying some pressure. The cover is replaced, and the plate is incubated at a temperature and for a time appropriate to the targeted microorganism or microbiota. After incubation, the colonies on each plate are counted and colony subculturing may follow. Since no sample dilution takes place, the RODAC method is suitable for sampling pre‐cleaned or sanitized surfaces. If the surface is contaminated heavily, incubated RODAC plates will be crowded with colonies and results will be difficult to interpret.