The microbiology of cold smoked salmon

Concurrent with the growth of aquaculture salmon farming, there is a corresponding increase in the commercial production of cold smoked salmon (CSS). The definition of CSS is vague, but it is normally made from salmon fillets with low levels of salt (<6% in the water phase) subjected to traditional wood smoking for prolonged periods, but not exceeding 25-30 °C during the process, or subject to artificial smoke flavoring by the application of liquefied smoke preparations formulated from condensation of wood smoke and either water, oil, or emulsifiers as e.g. polysorbate. The present review summarizes recent literature with respect to microbiological quality and safety of modern, commercial CSS, including factors controlling these parameters, and emerging trends and risk analysis measures to improve them. Special weight is put on the use of salt and alternative organic salt formulations, their combination, and use in hurdle technology to improve the safety of CSS, which is in turn primarily dictated by the pathogen Listeria monocytogenes, but also Clostridium botulinum, and their growth potential related to their salt and temperature tolerance. The microbiological quality and shelf life of CSS is, dependent on packaging method and storage temperature, determined mostly by the presence of lactic acid bacteria and the primary spoilage bacteria Shewanella putrefaciens, Photobacterium phosphoreum, Pseudomonas spp., and marine Vibrio. Additionally, parasites and microbiologically derived biogenic amines relevant to CSS are briefly discussed.