Biomedical Engineering Reference
In-Depth Information
antimicrobial packed cooked ham resulted in
L. monocytogenes
levels below the
detection limit (day 90). On the other hand, storage at 1 °C controlled the growth of
the pathogen until day 39 in non-pressurized ham, while antimicrobial packaging
and storage at 1 °C exerted a bacteriostatic effect for 60 days.
Culture-dependent and culture-independent approaches were used to reveal the
microbial diversity and dynamic changes occurring in sliced vacuum-packed cooked
ham after high pressure processing (400 MPa or 600 MPa for 10 min at 22 °C) dur-
ing refrigerated storage over 90 days (Han et al.
2011
). The predominant spoilage
organisms of cooked ham, such as
L. sakei
and
L. curvatus
, were found to be very
sensitive to pressure as they were unable to be detected in HPP samples at any time
during refrigerated storage.
Weissella viridescens
and
Lc. mesenteroides
survived
HPP at 600 MPa and were responsible for the fi nal spoilage. It was concluded that
high pressure processing at 400 or 600 MPa for 10 min at room temperature (22 °C)
has a powerful inhibitory effect on the major spoilage bacteria of sliced vacuum-
packed cooked ham.
Effects of enterocins A and B and sakacin K, nisin, potassium lactate, and a com-
bination of nisin and lactate incorporated interleavers, against
L. monocytogenes
spiked in sliced, cooked ham was evaluated (Jofré et al.
2007
). This was followed
by high-pressure processing at 400 MPa. HPP of actively packaged ham slices
reduced
Listeria
populations about 4 log cfu/g in all batches containing bacterio-
cins. At the end of storage,
L. monocytogenes
levels in the bacteriocin-containing
batches were the lowest, with counts below 1.51 log cfu/g. In contrast, HPP moder-
ately reduced
L. monocytogenes
counts in the control and lactate batches, with pop-
ulations gradually increasing to about 6.5 log cfu/g at the end of storage. Later, the
effectiveness of the application of interleavers containing enterocins A and B, saka-
cin K, nisin A, potassium lactate and nisin plus lactate alone or in combination with
a 400 MPa high hydrostatic pressure treatment was assessed in sliced cooked ham
spiked with
Salmonella
spp. (Jofré et al.
2008a
). HHP produced a signifi cant reduc-
tion in
Salmonella
counts, but the elimination of the pathogen could only be
achieved by combining HHP and nisin-containing interleavers. Thus, antimicrobial
packaging, HHP and refrigerated storage appeared as an effective combination of
hurdles to obtain value added ready-to-eat products with a safe long-term storage.
The effectiveness of the combination of high pressure processing (600 MPa)
with the natural antimicrobials nisin and potassium lactate has been evaluated in
sliced cooked ham spiked with 4 log cfu/g of
Salmonella
spp.,
L. monocytogenes
and
S. aureus
after 3 months of storage at 1 and 6 °C (Jofré et al.
2008b
). In non-
HPP sliced cooked ham, the addition of nisin plus lactate inhibited the growth of
L. monocytogenes
during the entire storage period while the refrigerated storage
inhibited the growth of
Salmonella spp
. and
S. aureus
. The application of an HPP
reduced the levels of
Salmonella
,
L. monocytogenes
and
S. aureus
. The combination
of HPP, nisin and refrigeration at 6 °C was found necessary to decrease the levels of
S. aureus
by 2.4 log cfu/g after 3 months of storage. Jofré et al. (
2009
) further
observed that addition of enterocins A and B to low acid fermented raw-sausages
spiked with 3 log cfu/g of
Salmonella
,
L. monocytogenes
and
S. aureus
reduced the
counts of
L. monocytogenes
, while
Salmonella
was more affected by the endogenous
