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Chapter 4
peracetic acid (100, 200, 400ppm) for inactivating E. coli, L. monocytogenes
and Salmonella biofilm cells formed on stainless steel and polyvinyl plastic
(PVC) over 6 days [207]. Parks et al. found that treatment with peracetic
acid was more effective than treatment with sodium hypochlorite for the 3
species examined. The results presented by Park et al. indicate that
exposure of Salmonella biofilm to 100mg/L of sodium hypochlorite for 5-50
minutes resulted in a ~1 log 10 reduction in the number of cells recovered
from steel. Exposure of the Salmonella biofilm to the same concentration
of peracetic acid results in a greater reduction after 50 minutes contact
time. However exposure to a higher concentration of peracetic acid
(200mg/L) for 10, 30 and 50 minutes resulted in a more significant
reduction in the number of S. Typhimurium cells recovered from the steel
surface (>4 log 10 reduction). A similar pattern for log 10 reduction was
reported when the PVC surfaces was used as a biofilm substratum [207]. It
may have been of use to also investigate if a higher concentration of
sodium hypochlorite would also reduce the number of cells recovered from
the surface.
Vestby et al. used a high working concentration of 0.05% (500mg/L)
sodium hypochlorite to investigate the log 10 reduction of a 48 hour
Salmonella biofilm cells recovered from glass slides after exposure time of
5 minutes [113]. The results indicated that there was a mean reduction of
2.4 log 10 of S. enterica cells recovered from the surface following treatment
for 5 minutes. However, in similar research by the same group Møretrø et
al. reported a mean log 10 reduction of 0.5-1.00 in the number of cells
recovered from the glass surfaces using the same method, product
containing sodium hypochlorite and similar S. Agona serovars (both S.
Agona strains isolated from a fish processing environment) [134].
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