Reductions of Listeria monocytogenes on cold-smoked and raw salmon fillets by UV-C and pulsed UV light

Salmon is the food most frequently reported in the RASFF (Rapid Alert System for Food and Feed) database in conjunction with Listeria monocytogenes and consumption of cold-smoked salmon have led to severe outbreaks of listeriosis infections. UV-C and pulsed UV light were investigated for their ability to reduce L. monocytogenes on salmon. Cold-smoked and raw salmon were spiked with a mix of ten L. monocytogenes strains (10(4) CFU/sample) and subsequently exposed to UV-C light (0.0075-0.6 J/cm(2)) or high intensity pulsed UV light (1.3-10.8 J/cm(2)). Reductions of L. monocytogenes on smoked salmon were 0.7-1.3 log, depending on the fluence. Corresponding reductions for raw salmon muscle side and skin side were 0.2-0.9 log and 0.4-1.1 log, respectively. Generally, reductions using UV-C and pulsed UV light were within the same range, but with some treatments statistically different. L. monocytogenes surviving UV treatments on smoked and raw salmon grew at the same rate as controls during storage at 4 degrees C, but reached the levels of the controls 13 and 7 days later, respectively. No sensory changes were detected in UV-C treated (0.05 J/cm(2)) smoked salmon. Industrial relevance: Due to the lack of critical control points in salmon production, it is not possible to ensure products that are consistently free from L. monocytogenes in the absence of mitigation strategies. Taking into account the reported generally low levels of L. monocytogenes on contaminated salmon, UV treatments should be considered important tools for the industry to contribute to lower prevalence and levels of Listeria. The present work on microbial and quality effects of UV-C and pulsed UV light treatments performed under industry relevant conditions on raw and cold-smoked salmon provides important information to the salmon industry for implementation of UV-light as risk reducing mitigation tools. This has key relevance for industry and consumers and will contribute to enhanced food safety, reduction of costly recalls and longer shelf-life.