Biomedical Engineering Reference
In-Depth Information
storage at 22 °C (Achemchem et al.
2006
). The bacteriocinogenic strain of
E. faecium
7C5 (which produces enterocin AS-48), added as an adjunct with a thermophilic
culture in soft cheese, led to complete death of
L. monocytogenes
and
L. innocua
without altering the acidifying activity of the starter culture (Giraffa et al.
1995b
).
When tested in cheeses, other strains producing enterocin AS-48 showed strong
inhibition of
L. monocytogenes
, as well as
B. cereus
and
S. aureus
(Núñez et al.
1997
; Muñoz et al.
2004
,
2007
). During the manufacture of Manchego cheese made
from raw ewe's milk,
E. faecalis
INIA 4 was able to compete with cheese microbi-
ota and produce enterocin (Núñez et al.
1997
). In cheeses inoculated with INIA 4
strain,
L. monocytogenes
Ohio counts were reduced below 1 log CFU/g in the rip-
ened cheese for up to 60 days. However,
L. monocytogenes
Scott A did not seem to
be affected by the inoculated enterocin-producer in the cheese. In a separate study,
when the enterocin AS-48 producer strain
E. faecalis
A-48-32 was co-inoculated
with
B. cereus
during cheese manufacture, viable cell counts of the bacilli were 5.6
log units lower than controls after 30 days of ripening (Muñoz et al.
2004
). The
effi cacy of strain A-48-32 against
S. aureus
was lower compared to
B. cereus
, but
staphylococci counts in treated cheeses remained at least 1 log CFU/g below con-
trols throughout at least 1 month storage (Muñoz et al.
2007
).
Enterococcus faecium
RZS C5 (a natural cheese isolate carrying the structural
genes for enterocins A, B and P) was reported to be effective as an anti-listeria
bacteriocin-producing co-culture in Cheddar cheese manufacture. The strains
Enterococcus mundtii
CRL35 and
E. faecium
ST88Ch isolated from cheeses were
tested for their capability to control growth of
L. monocytogenes
426 in experimen-
tally contaminated fresh Minas cheese during refrigerated storage (Vera Pingitore
et al.
2012
). Growth of
L. monocytogenes
426 was inhibited in cheeses containing
E. mundtii
CRL35 up to 12 days at 8 °C, stressing the potential of this strain for
application in Minas cheese. However,
E. faecium
ST88Ch was less effective in the
control of listeriae.
Strains of enterococci and lactococci producing bacteriocins (such as enterocins
I, TAB 7, TAB 57, AS-48, nisin A, nisin Z and lacticin 481) have been tested in
combination with HHP treatments with the aim to improve the safety of cheeses
made from raw milk. Inoculation of milk with bacteriocinogenic strains before
cheese making followed by application of HHP treatment to the cheeses was
reported to increase the bactericidal activity against
L. monocytogenes, S. aureus
and
E. coli
O157:H7. For example, for 300 MPa treatment (10 min), counts of
L. monocytogenes
were always lower in the cheeses inoculated with the bacteriocin-
producing enterococci both on day one after treatment and also after 60 days of
ripening (at 12 °C under vacuum). For
S. aureus
, inoculation of cheeses with
bacteriocin-producing enterococci also improved the lethal effects of HHP treat-
ments (Arqués et al.
2005b
). When similar treatments (300 MPa, 10 min; 500 MPa,
5 min) were applied to cheeses challenged with
E. coli
O157:H7, the reductions
obtained for the treatment at 300 MPa were in the range of 0.7-2 log CFU/g on day
one after treatment and 0.2-1.2 log CFU/g after 60 days as compared to the controls
not inoculated with bacteriocin producers (Rodríguez et al.
2005
). For 500 MPa,
greatest differences were observed at day one after treatment, with in which no viable
