Biomedical Engineering Reference
In-Depth Information
Enterocins have also been tested in cooked meat products. Addition of a partially-
purifi ed preparation of enterocins A and B (4,800 AU/g) reduced the numbers of
L.
innocua
by 7.98 log cycles in cooked ham and by 9 log cycles in pork liver paté
stored at 7 °C for 37 days (Aymerich et al.
2000
). In vacuum packaged sliced cooked
pork ham, added enterocins A and B (128 AU/g) inhibited the production of slime
by
Lactobacillus sakei
CTC746 strain, but not by
Leuconostoc carnosum
CTC747
strain (Aymerich et al.
2002
).
Results from studies on the synergistic activities of bacteriocins with other anti-
microbials and on the effect of immobilized preparations or application of bacterio-
cins by dipping solutions, together with the technical advances in the development
of activated supports opened the doors for application of immobilized bactericin
preparations or activated packagings containing cocktails of antimicrobial sub-
stances on RTE meats (Coma
2008
). Bacteriocin-activated fi lms may be quite use-
ful for cooked meat products, not only because they can prolong the product shelf
life by decreasing the risks of spoilage and growth of pathogens from cross-
contamination during processing, but also because the fi lm itself acts as a barrier
against external contamination of the processed product. Among the various kinds
of edible coatings tested on vacuum-packaged products (hot dogs, frankfurters, or
ham) best results have been reported for coatings containing nisin in combination
with other antimicrobials under refrigeration storage.
Application of zein coatings containing nisin, sodium lactate, and sodium diace-
tate completely eliminated
L. monocytogenes
on turkey frankfurters during refrig-
eration storage (Lungu and Johnson
2005
). In hot dogs that were vacuum-packaged
in fi lms coated with nisin,
L. monocytogenes
counts decreased during refrigeration
storage (Franklin et al.
2004
). Hot dogs were placed in control and nisin-containing
pouches and inoculated with a fi ve-strain
L. monocytogenes
cocktail (approximately
5 log CFU per package), vacuum sealed, and stored for intervals of 2 h and 7, 15, 21,
28, and 60 days at 4 °C. In hot dogs packaged in fi lms coated with 2,500 IU/ml nisin
solution, nisin signifi cantly decreased (
P
< 0.05)
L. monocytogenes
populations on
the surface of hot dogs by greater than 2 log CFU per package throughout the
60-days study. However,
L. monocytogenes
populations still remained at approxi-
mately 4 log CFU per package after 60 days of refrigerated storage (Franklin et al.
2004
). This study reported similar results when using a cellulose-based coating solu-
tion (based on methylcellulose/hydroxypropyl methylcellulose) containing nisin.
However, in another study nisin-coated cellulose casings showed only moderate
antilisterial activity in vacuum-sealed frankfurters, unless additional antimicrobials,
such as potassium lactate and sodium diacetate, were employed (Luchansky and
Call
2004
). Nguyen et al. (
2008
) carried out similar experiments using an edible
bacterial cellulose fi lm containing nisin to control
L. monocytogenes
and total aero-
bic bacteria on the surface of vacuum-packaged frankfurters. The frankfurters pack-
aged in fi lms activated with 2,500 IU/ml showed signifi cantly lower counts of
L. monocytogenes
and total aerobic plate counts during refrigerated storage for 14
days as compared to the controls. The authors concluded that activated cellulose
fi lms had potential applicability as antimicrobial packaging fi lms or inserts for pro-
cessed meat products. Another study reported that polythene fi lms activated with
