Reduction of Listeria monocytogenes in cold-smoked salmon by bacteriophage P100, nisin and lauric arginate, singly or in combinations

Three GRAS antimicrobials including, lauric arginate (LAE), bacteriophage P100 (phage P100) and bacteriocin nisin, were evaluated either singly or in combinations for the reduction of initial load of Listeria monocytogenes in cold-smoked salmon (CSS). The stability of phage P100 in the presence of LAE (200 ppm) and nisin (500 ppm) or at 10x and 100x of these concentrations was determined at 4 degrees C or 30 degrees C for 24 h in a broth model. Phage P100 was found to be highly stable in the presence of these antimicrobial agents as plaque-forming units (PFU) did not vary between control and antimicrobial-treated phage. The survival of L. monocytogenes in the presence of phage P100, nisin and LAE showed remarkable reduction within 24 h both at 4 degrees C or 30 degrees C in broth. Treatment of CSS containing 3.5 log CFU cm(-2) L. monocytogenes with phage P100 (10(8) PFU mL(-1)), nisin (500 ppm) and LAE (200 ppm) showed strong listericidal action and reduced the L. monocytogenes by 2-3 log CFU cm(-2) after 24 h. Among the combined treatments, phage P100 + LAE or nisin + LAE exhibited the most listericidal action in which L. monocytogenes cells were reduced to undetectable level within 24 h in CSS.