Biomedical Engineering Reference
In-Depth Information
The authors of this study concluded that encapsulation of bacteriocins in liposomes
of partially purifi ed soybean phosphatidylcholine may be a promising technology
for the control of foodborne pathogens in cheeses.
Processing of dairy foods, such as cheese slicing, can be a critical point for bacte-
rial contamination. For application on sliced cheeses, nisin immobilized in polyeth-
ylene/polyamide packagings was shown to reduce the population of LAB,
L.
innocua
and
S. aureus
on the cheese slices packaged with the activated interleaves
(Scannell et al.
2000
). Also, when nisin immobilized in sodium caseinate fi lms was
tested against
Listeria
inoculated on the surface and in depth on mini red Babybel
soft cheese, the presence of the active fi lm resulted in a 1.1 log CFU/g reduction in
L. innocua
counts on the cheese surface after 1 week of storage at 4 °C as compared
to control samples (Cao-Hoang et al.
2010
). Inactivation rates decreased as depth of
inoculation increased, e.g. 1.1, 0.9 and 0.25 log CFU/g for distances from the con-
tact surface of 1, 2, and 3 mm, respectively, refl ecting the nisin diffusion gradient.
The study concluded that nisin immobilized in sodium caseinate fi lms a promising
method to overcome problems associated with post-process contamination, thereby
extending the shelf life and possibly enhancing the microbial safety of cheeses.
Added lacticin 3147 powder rapidly inactivated
L. monocytogenes
and reduced
S. aureus
viable cell counts in an infant milk formulation, and was highly effective
against
L. monocytogenes
in natural yogurt and in Cottage cheese (Morgan et al.
2001
). Addition of 10 % lacticin 3147 powder reduced the concentration of viable
Listeria
below detectable levels in yogurt within 60 min or killed 85 % of cells in
cottage cheese within 120 min (Morgan et al.
2001
). However, optimisation of lac-
ticin 3147 powder to increase specifi c activity may be necessary in order to decrease
the amount of added powder required for an effective microbial inhibition.
Several enterococal bacteriocins have been tested for preservation of dairy foods
(Giraffa
1995
; Foulquié Moreno et al.
2006
; Gálvez et al.
2008
). Enterocins CCM
4231, CRL35, or AS-48 can reduce the levels of
L. monocytogenes, S. aureus
or
B. cereus
in dairy products. A concentrated enterocin CRL35 preparation added to goat cheese
(10,400 AU/ml) reduced the population of
L. monocytogenes
by 9 log units by the
end of ripening period without affecting the cheese quality (Farías et al.
1999
).
Lauková et al. (
1999
) reported that addition of enterocin CCM 4231 (3,200 AU/ml)
in yogurt milk inoculated with
L. monocytogenes
reduced the levels of listeria after
24 h incubation at 30 °C by about 2 log CFU/ml. Similarly, enterocin addition
(3,200 AU/ml) to skim milk decreased the viable counts of
S. aureus
from 10 log
CFU/ml to 2 log CFU/ml after 24 h incubation of milk at 27 °C. This bacteriocin
also reduced the levels of
Listeria
in “bryndza” (a traditional Slovak soft cheese
from sheep milk) and Saint-Paulin cheese (Lauková et al.
2001
; Lauková and
Czikková
2001
) but it did not achieve complete elimination of the bacteria. For
example, addition of enterocin CCM 4231 during Saint-Paulin cheese preparation
(3,200 AU/ml) reduced the population of inoculated
L. monocytogenes
by almost 5
log cycles for up to 1 week, followed by proliferation of the listeria afterwards(Lauková
et al.
2001
).
Bcteriocins from enterococci have been used to prepare activated fi lms or coat-
ings for use in the cheese industry. In one study, Iseppi et al. (
2008
) tested the anti-
