Application of replica plating and computer analysis for rapid identification of bacteria in some foods. II. Analysis of microbial flora in irradiated Dover sole (Microstomus pacificus).

This investigation was carried out to determine the nature of the microbial flora shifts in dover sole as a result of irradiation and storage at 6 C. The relationship was determined between the microorganisms which initially survive irradiation and those making up the final spoilage flora. A total of 2,723 isolates were examined by use of the replica-plating and computer analysis method. The spoilage of the unirradiated control samples during storage at 6 C was almost entirely due to the growth of Pseudomonas. This group, which occupied 25% of the fresh flora, grew to nearly 100% in 2 days of storage. In contrast, irradiation doses of 0.1, 0.2, 0.3, and 0.4 Mrad favored the growth of Achromobacter and yeasts. The Micrococcus, which survived radiation, did not grow at 6 C. At 0.5 Mrad, spoilage of fish samples was due entirely to the growth of yeasts.