The objective of this study was to determine if a gentle rinse procedure was equivalent to the combination of excision and homogenization with a stomacher for the relative removal of various microorganisms
from finfish fillets. Fillets of hybrid striped bass and rainbow trout were obtained from local markets and sampled using three methods: rinse (R), excision followed by homogenization in a stomacher (S),
and homogenization of fillets following a rinse (RS). Microorganisms were enumerated on selective and nonselective media, and randomly selected colonies from aerobic plate counts were identified using MIDI
Sherlock and BIOLOG microbial identification systems. Enrichments and selective media were used for the isolation of Listeria monocytogenes, Salmonella spp., and Yersinia enterocolitica.
This study confirms previous reports that stomaching is superior to rinsing for enumerating total microbial populations from fish fillets. Rinsing was more effective for rainbow trout than for striped bass.
Sampling method did not affect the relative magnitude of plate counts on media selective for aeromonads, pseudomonads, Shewanella, lactic acid bacteria, enterics, and gram-positive cocci. In the
compositional analysis of random isolates, R recovered significantly lower fractions of aeromonads than did S or RS, but sampling method did not affect the percent recovery of lactic acid bacteria, pseudomonads,
Shewanella, Moraxellaceae, or Cytophaga/Flavobacterium. However, observations suggest that with increased replication, differences among Moraxellaceae, Pseudomonas, and gram
positives might be significant. Only one L. monocytogenes colony was isolated, and no Salmonella or Y. enterocolitica, so the effect of sampling method could not be determined for these
organisms. Differences in predominant bacterial populations were seen between fish species.
Document Type: Research Article
University of Maryland, Department of Animal and Avian Sciences, College Park, Maryland 20770, USA
Publication date: October 1, 2001
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