3.1.3. Smoked salmon
Smoked salmon was experimentally contaminated and treated
with ListShield™ at an application rate of 9 105 PFU/g or
2 106 PFU/g and the amount of viable L. monocytogenes was
assessed after 24 h at 4 C (Fig. 1B). The lower application rate
resulted in a 65% (0.4 log) reduction of viable L. monocytogenes
compared to the control sample. At the higher application rate, a
90% (1.0 log) reduction was noted. While the effect at either
application rate was significantly different than the control
(p < 0.05 for the lower application rate and p < 0.01for the higher
application rate), the higher application rate did not result in a
statistically significant decrease in the amount of viable
L. monocytogenes compared to the lower application rate. These
observations are in general agreement with those reported earlier
for raw salmon applications, where phages reduced the levels of
L. monocytogenes by 0.8e3.5 log (Guenther et al., 2009; Soni and
Nannapaneni, 2010). The better reduction in the L. monocytogenes
levels reported by Guenther et al. (2009), at a similar inoculum
level, could be due to a higher phage application rate of
3 108 PFU/g compared to that used in our study, further supporting
the idea that the efficacy of phage treatment is phage
concentration-dependent (Guenther et al., 2009).