Cold-smoked (Salmo salar) salmon samples were surface-inoculated with a cocktail of three nisin-resistant strains of L. monocytogenes (PSU1,
PSU2 and PSU21) to a level of approximately 5×102 or 5×105 CFU/cm2 of salmon surface. The inoculated smoked salmon samples were vacuumpackaged
with control film (no nisin) or nisin-coated plastic films and stored at either 4 or 10 °C. When the inoculated smoked salmon samples were
packaged with film coated with 2000 IU/cm2 of nisin, a reduction of 3.9 log CFU/cm2 (compared with control) was achieved at either temperature for
samples inoculated with 5×102 CFU/cm2 of L. monocytogenes after 56 (4 °C) and 49 (10 °C) days of storage while reductions of 2.4 and 0.7 log
CFU/cm2 were achieved for samples inoculated with a high level of L. monocytogenes (5×105 CFU/cm2) after 58 (4 °C) and 43 (10 °C) days,
respectively. For samples packaged in film coated with 500 IU/cm2 of nisin, reductions of 0.5 and 1.7 log CFU/cm2 were achieved for samples
inoculated with a low level of L. monocytogenes (5×102 CFU/cm2) after 56 (4 °C) and 49 (10 °C) days of storage while reductions of 1.8 and 0.8 log
CFU/cm2 were achieved for samples inoculated with high level of L. monocytogenes after 58(4 °C) and 43 (10 °C) days, respectively. In addition,
nisin inhibited the proliferation of background microbiota on smoked salmon in a concentration-dependent manner at both storage temperatures
although the bacteriostatic effect was more pronounced at refrigeration temperature. This work highlights the potential for incorporating nisin into
plastic films for enhancing the microbial safety of smoked salmon as well as controlling its microbial spoilage.
© 2007 Elsevier B.V. All rights reserved.