61C-9 |
Spoilage potentials of Pseudomonas ribotypes and their ecology in dairy plants |
B. DOGAN, M. Wiedmann, and K. J. Boor. Food Science, Cornell University, 415 Stocking Hall, Ithaca, NY 14853 Pseudomonas spp. are common spoilage microorganisms of refrigerated fluid milk products. In this study, our objectives were i) to track the ecology of Pseudomonas spp. in milk products and the dairy environment. and ii) to determine the association between genetic types (ribotypes) of Pseudomonas and their ability to cause spoilage (i.e., production of proteolytic and lipolytic enzymes) A total of 338 Pseudomonas spp. were isolated from raw and pasteurized milk and from environmental samples of four dairy processing plants. The majority of isolates were identified as P. fluorescens and P. putida by API-20 NE. A total of 42 different ribotype patterns were found among 81 isolates ribotyped. The presence of multiple ribotypes indicated considerable ecological diversity within the dairy environment. Except for one ribotype, the ribotype patterns of the isolates from milk collected in the first plant visit did not resemble the patterns from isolates collected in the second plant visit, which suggests short-term colonization of Pseudomonas spp. Enzymatic activity of the Pseudomonas isolates differed in a manner consistent with ribotype pattern. Isolates that had the same ribotype frequently had the same protease, lecithinase and lipase activities. Our results suggest that lecithinase and lipase activities are closely related with 76% of the isolates having both lecithinase and lipase activities or neither activity. We found that ribotyping is a discriminatory typing method for Pseudomonas spp. and reliably identifies strains with food spoilage potential.
Session 61C, Food Microbiology: General I
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