Nisin and ALTA™ 2341 inhibit the growth of Listeria monocytogenes on smoked salmon packaged under vacuum or 100% CO2

The effects of nisin and ALTA(TM) 2341 on the growth of Listeria monocytogenes were assessed on smoked salmon packaged under vacuum or 100% CO2. Smoked salmon slices (pH 6.3) were inoculated with a cocktail of seven L. monocytogenes isolates at a level of approximately 2.5 log(10) colony forming units (cfu) g(-1). After inoculation, the surface of the smoked salmon slices was treated with either nisin (400 or 1250 IU g(-1)) or ALTA(TM) 2341 (0.1 or 1%). The smoked salmon was packaged and stored at 4 degrees C (28 d) or 10 degrees C (9d). On untreated vacuum-packaged smoked salmon, L. monocytogenes grew by 3.8 log(10) cfu g(-1) at 4 degrees C and 5.1 log(10) cfu g(-1) at 10 degrees C. Growth was reduced on nisin- and ALTA(TM) 2341-treated vacuum-packaged smoked salmon. On the nisin-treated samples, L. monocytogenes increased by 2.5 (400 IU g(-1)) and 1.5 (1250 IU g(-1)) log(10) cfu g(-1) at 4 degrees C, and by 4.3 (400 IU g(-1)) and 2.7 (1250 IU g(-1)) log(10) cfu g(-1) at 10 degrees C. With the ALTA(TM) 2341-treated samples, L. monocytogenes increased by 2.8 (0.1%) or 1.6 (1.0%) log(10) cfu g(-1) at 4 degrees C, and 3.3 (0.1%) or 3.6 (1.0%) log(10) cfu g(-1) at 10 degrees C. The growth of L. monocytogenes was retarded by packaging the smoked salmon in 100% CO2. On untreated smoked salmon only a 0.8 log10 cycle increase was observed at 10 degrees C. Under all the other conditions tested with 100% CO2, L. monocytogenes was detected but growth was prevented.