Evaluation of tools for control of Listeria in salmon and salmon products

Summary

The aim of the project was to provide documentation on methods to reduce Listeria on salmon. Methods and technologies that were considered to meet important criteria for Listeria effects and applications were selected for testing and evaluation. Particular focus was on the use of UV-illumination to kill Listeria and salts of organic acids/fermentate to inhibit Listeria growth on raw and smoked salmon. Combined UV-treatments and use of fermentate provided both kill and Listeria inhibition in smoked salmon and with minor changes in sensory effects. Evaluated technologies also included acidic sodium chlorite on raw salmon, and nisin and bacteriophages (PhageGuard Listex) used alone and in combination with fermentate. The results showed that UV light, nisin and Listex reduced Listeria levels on salmon by about 0.5-3 log units but did not inhibit growth of surviving Listeria. Salts of organic acids/fermentate can provide effective Listeria growth inhibition although dependent on the compounds applied. Treatment of raw salmon with acidic sodium chlorite showed limited effects on Listeria reduction. Simple cost-benefit assessments indicate that the implementation of technologies/methods for treatment of salmon can provide reduced Listeria occurrences/levels on salmon within reasonable cost limits, but further optimization and calculations are needed for optimal application and effects of such measures. The project was funded by FHF- Norwegian Seafood Research Fund and was carried out in good dialog with the salmon industry.