Biomedical Engineering Reference
In-Depth Information
bacteriocin 32Y from
L. curvatus
were effective in reducing the population of listeria
in vacuum-packaged frankfurters during storage at 4 °C (Ercolini et al.
2006
). By
using viable staining and fl uorescence microscopy, the authors corroborated that the
activated fi lm caused an immediate reduction of live and appearance of dead cells
just after 15 min from the packaging.
Another suggested application of nisin is the preservation of natural sausage cas-
ings. Casings derived from animal intestines can be one possible route for transmis-
sion of
C. perfringens
spores and other sulphite-reducing anaerobic spores, since
the brining process of intestines does not inactivate bacterial endospores. In one
study, it was shown that nisin was partly reversibly bound to casings and can reduce
the outgrowth of
Clostridium sporogenes
spores in the model used by approxi-
mately 1 log cycle (Wijnker et al.
2011
). This could open new possibilities to com-
bat the entry of pathogens in the food chain.
In vacuum-packaged cooked ham, application of a gelatine coating gel contain-
ing a combination of lysozyme, nisin and EDTA in showed bactericidal activity for
B. thermosphacta
,
L. sakei
,
L. mesenteroides
,
L. monocytogenes
and
S. enterica
serovar Typhimurium (Gill and Holley
2000b
). In sliced cooked ham packaged
under MAP and stored at 4 °C, the inclusion of polyethylene/polyamide inserts
coated with nisin (approximately 2,560 AU cm
2
) reduced the levels of LAB,
Listeria
innocua
and
Staphylococcus aureus
, and partially inhibited growth of total aerobic
bacteria on the ham during storage (Scannell et al.
2000b
). However, in ham steaks
packaged in chitosan-coated plastic fi lms containing 500 IU/cm
2
of nisin, the low
bacteriocin concentration tested was ineffective in inhibiting
L. monocytogenes
(Ye
et al.
2008
).
Pediocin immobilization has also shown variable results. Encapsulation of
pediocin AcH in liposomes enhanced its antimicrobial activity in meat slurries
(Degnan and Luchansky
1992
). However, in another study, when pediocin adsorbed
to its heat-killed producer cells was used to treat sliced frankfurters before packag-
ing, the number of
L. monocytogenes
decreased during 6 days of storage, but
remained at constant levels for the remaining storage period (up to 21 days), indicat-
ing that the pediocin preparation was not effi cient enough to kill all
L. monocyto-
genes
(Mattila et al.
2003
). The effi cacy of cellulose fi lms containing pediocin
PA-1/Ach (ALTA
®
2351) against
L. innocua
and
Salmonella
sp. was tested on sliced
ham packaged under vacuum and stored at 12 °C simulating abusive temperatures
that can occur in supermarkets (Santiago-Silva et al.
2009
). The antimicrobial fi lms
were more effective inhibiting growth of
L. innocua
(with a growth reduction of 2
log cycles compared to control treatment after 15 days of storage) than
Salmonella
(0.5 log cycle reduction in relation to control, after 12 days). However, the viable
cell concentrations of the inoculated bacteria were not reduced for any of the
treatments.
Films activated with enterocin 496K1 (from
Enterococcus casselifl avus
IM
416K1) and enterocins A and B have been tested in ready to eat meat products
(Iseppi et al.
2008
; Marcos et al.
2007
). Enterocin 416K1 activated fi lms reduced
the levels of
L. monocytogenes
in contaminated frankfurters by ca. 1.5 to 0.5 log
cycles within 24 h of storage at temperatures of 4 and 22 °C, but did not avoid expo-
