| Summary: | Listeria monocytogenes is a common post-processing contaminant in ready-to-eat vacuum packaged (VP) cold smoked salmon. Since this psychrotrophic pathogen can grow at refrigerated temperatures (~4°C), other safety barriers in addition to temperature are needed to ensure the continued safety of VP cold smoked salmon. One such novel barrier could be the pulsed light (PL) treatment of the product prior to packaging or treating the product through a transparent package. === Pulsed light destruction kinetics of L. monocytogenes were evaluated while dispensed into a liquid media, on the surface of a general purpose agar and on the surface of cold smoked salmon. Results showed that PL technology was an effective surface sanitation method (a decimal reduction time or D-value of 0.91, 1.37 and 2.25 s exposure of PL at 800, 700 and 600 V, respectively, and a resulting z value of 500 V) on the agar plate. However, it had only a limited success when applied to liquid samples as well as directly on the surface of cold smoked salmon (D-value ranged from 93 s to 24 min). === Sensory quality of VP cold smoked salmon subjected to selected PL treatments was monitored during storage for 14 days at 4°C. Both color and odor scores remained within acceptable limits over the 14 day storage period. Subsequent challenge studies were carried out with L. monocytogenes applied on VP cold smoked salmon. An overall reduction in counts was observed in samples stored at 4°C over 28 days; however, after PL treatment (day 0), there was no significant reduction in counts. Color and odor scores maintained acceptable values over 14 days. Additional experiments were carried out to determine the effects of (1) 1.5% salt, (2) 6% oil, (3) a representative salmon media and (4) background microflora (lactic acid bacteria) on the PL inactivation of L. monocytogenes. All of these factors significantly affected the destruction of L. monocytogenes by increasing the D-value (adding resistance to pulsed light destruction). === Overall, these studies have shown that PL treatment in combination with low temperature storage (4°C) has the potential to extend the shelf-life of VP cold smoked salmon products without compromising sensory quality. However further investigation into higher treatment voltages is necessary in order to achieve a higher target kill of L. monocytogenes.
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