Plantaricin 35d, a biopreservative for the control of Listeria monocytogenes in smoked salmon samples

The antibacterial activity of plantaricin 35d - a bacteriocin produced by the lactobacillus strain Lactobacillus plantarum 35d, isolated from seasoned sausages - has been evaluated against eight strains of Listeria monocytogenes. The active substance has been characterized and the results showed: the optimal temperature for production, the kinetics of growth, the mode of action, the heat-resistance, the stability to time and to different pH values. Subsequently the crude extract substance or the producer micro:organism was added, as biopreservative, in smoked salmon samples artificially contaminated with L, monocytogenes of different source and the bacterial counts during the shelf-life period were evaluated. The study confirmed the active growth of L. monocytogenes in salmon samples at refrigerated temperature whereas the treated samples presented a trend growth lower about 1-3 log during the same period of time. In both tests the difference between the bacterial count remained notable until and over the sixteenth week.