Biomedical Engineering Reference
In-Depth Information
were refrigeration stored under normal, vacuum, or modifi ed atmosphere packag-
ing. The application of enterocin AS-48 did not reduce the mesophilic, psychrotro-
phic, or Gram-negative bacteria viable cell counts under any of the storage conditions
tested. AS-48 did cause signifi cant reductions in viable staphylococci counts, espe-
cially under vacuum packaging. Storage of samples treated with enterocin AS-48
under modifi ed atmosphere or under vacuum packaging allowed reductions (signifi -
cant at some storage times) in histamine- and tyramine-forming LAB. The most
interesting results of this study are those concerning the observed decrease (by sev-
eral fold) in the levels of the biogenic amines cadaverine, putrescine, tyramine, and
histamine determined after treatment with AS-48.
Antibacterial activity with broad inhibitory spectrum (
Arthrobacter
sp.,
Acinetobacter
sp.,
Bacillus subtilis
,
Escherichia coli
,
L. monocytogenes
,
Pseudomonas aeruginosa
and
Staphylococcus aureus
) was detected in
Lactococcus
lactis
PSY2 isolated from the body surface of marine perch (Sarika et al.
2012
).
Surface-application of a bacteriocin preparation derived from this strain on fi llets of
reef cod reduced bacterial growth during storage at 4 °C. The total viable count
revealed that PSY2-treated fi sh samples remained within the maximum limit of
acceptability (10
7
counts/g, according to International Commission of
Microbiological Standards for Foods 1986) until day 21, while the untreated con-
trols became unacceptable before the 14th day of storage (Sarika et al.
2012
). The
maximum inhibitory effect of bacteriocin PSY2 was observed against
Staphylococcus
sp. and
Pseudomonadaceae
which were reduced by 1.8 and 3.37 log units in the
PSY2 treated fi llets compared to the control. Acceptability in terms of sensory attri-
butes was signifi cantly higher in the bacteriocin-treated samples.
Data on bacterial food poisoning associated to consumption of seafoods are
comparatively more scarce compared to data on incidence of
L.monocytogenes
.
However, a recent study reported that enterotoxigenic
Bacillus cereus
can grow on
the surface of fresh salmon at abusive temperatures, with generation times of 169.7,
53.5, and 45.6 min were at 12, 16, and 20 °C (Labbé and Rahmati
2012
).
Nonhemolytic enterotoxin was detected on salmon after 20 h at 20 °C and after 26 h
at 16 °C when levels of
B. cereus
were in excess of 10
8
CFU/g, indicating that fresh
salmon can serve as an excellent substrate for enterotoxigenic
B. cereus
and that this
organism can reach levels associated with foodborne illness following moderate
temperature abuse (Labbé and Rahmati
2012
). Nisin, at concentrations of 1 and
15 mg/g of salmon, reduced the levels of
B. cereus
by 2.5- and 25-fold, respectively
after 48 h incubation at 16 °C, although the effect of added nisin on enterotoxin
production was not reported (Labbé and Rahmati
2012
).
7.1.2
Ready-to-Eat Seafoods
Minimally processed refrigerated ready-to-eat seafoods can pose health risk to sus-
ceptible individuals due to contamination by
L. monocytogenes
. Proliferation of
L. monocytogenes
in slightly processed products which are consumed without
