Lactic acid bacteria as protective cultures against Listeria spp. on cold-smoked salmon

Three bacteriocin producing (Bac(+)) strains of Lactobacillus sakei were used singly and in combination with each other as protective cultures to control the growth of listeria in cold-smoked salmon. Challenge experiments were conducted under practical conditions in a smokehouse. The surface of salmon sides was inoculated with 10(4) cfu/g of Listeria innocua and 10(7) cfu/g of Bac(+) lactic acid bacteria as well as a L. sakei Bac(-) control. After smoking the counts of listeria and lactic acid bacteria were determined at days 1 and 14. All Bac(+) L. sakei strains reduced the counts of L. innocua by > 2 log units. Strain LTH5754 was an isolate from cold-smoked salmon and achieved even a 5 log reduction of L. innocua within the storage period. In vitro experiments showed, that the Bac(+) strains were also effective against L. monocytogenes (three strains tested) and L. ivanovii (1 strain). The pH as well the sensorial properties of the smoked salmon were not affected by the L. sakei inocula.