Bacteriological quality of aquacultured freshwater fish portions in prepackaged trays stored at 3 degrees C

Fresh trout fillets and salmon slices packed in trays were obtained from tw o multinational chain supermarkets and evaluated for freshness and bacterio logical quality immediately after packaging and during storage at 3 degrees C. Initial aerobic counts at 30 and 25 degreesC were significantly (P < 0.0 5) lower in trout fillets (5.27 +/- 0.57 and 4.87 +/- 0.80 log CFU/g, respe ctively) than in salmon slices, where levels in excess of 6 log CFU/g were found. In both products, initial Enterobacteriaceae counts were slightly hi gher than 3 log CFU/g and increased significantly during shelf life by appr oximately 3 log CFU/g. Most of the enterobacteria were identified as Citrob acter freundii, Hafnia alvei, and Enterobacter cloacae. On day 0, most prob able number (MPN) counts of total and fecal coliforms were not significantl y different, numbers of the latter group being approximately 4 MPN/g. Esche richia coli was only detected when fish was spoiled. Although initial presu mptive Staphylococcus aureus counts were approximately 3 log CFU/g, only 4 of 84 selected colonies belonged to this species. Neither Salmonella nor an timicrobial residues were detected in any sample. Ethanol content in salmon slices did not significantly (P > 0.05) increase until they became inedibl e. Significant correlation (r = +0.72, P < 0.05) was observed between this chemical index and viable counts at 30 degreesC only when salmon slices wer e inedible. Trout fillets were acceptable for 7 days, and salmon slices sho wed signs of spoilage after 4 days. Although public health concerns associa ted with packed trout and salmon appear to be minimal, data on sensory qual ity, shelf life, and total viable and Enterobacteriaceae counts strongly su ggest the need to improve the quality control systems used by European mult inational retailers, especially for imported salmon.