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Anti-listerial inhibitory lactic acid bacteria isolated from commercial cold smoked salmon

Tome, E., Teixeira, P., Gibbs, P.A.
Food microbiology 2006 v.23 no.4 pp. 399-405
smoked fish, salmon, microorganisms, isolation, lactic acid bacteria, secondary metabolites, bacteriocins, food preservatives, antibacterial properties, food spoilage, food pathogens, Listeria monocytogenes, microbial competition, competitive exclusion, phenotype, taxonomy, cold tolerance, vacuum packaging, shelf life, food microbiology
The natural microflora of cold-smoked fish at the end of shelf-life are lactic acid bacteria (LAB). Some of these display a capacity to inhibit spoilage as well as several strains of pathogenic micro-organisms, e.g. Listeria monocytogenes which is isolated frequently from cold-smoked salmon (CSS). Eight batches of sliced vacuum-packed CSS from Norway, Scotland and Spain were collected at retail. Packs were stored at 5 °C and examined for chemical and microbiological characteristics, at purchase date and at expiration date. pH, water activity and salt content were similar to available data on lightly preserved fish products. There was a consistent pattern in the development of the microflora on CSS; the initial level of LAB was low on freshly produced CSS (10(2) cfu g-1); however, storage in vacuum packaging at refrigeration temperature was elective for LAB. At the end of the stated shelf-life these micro-organisms, represented mainly by Lactobacillus spp., attained ca.107 cfu g-1 while Enterobacteriaceae counts were consistently lower (10(5) cfu g-1), which indicates the ability of LAB to grow and compete with few carbohydrates available and in the presence of moderate salt concentrations. L. monocytogenes was not found in any sample.