Biomedical Engineering Reference
In-Depth Information
bination with nisin (500 IU/cm
2
) inhibited the proliferation of
L. monocytogenes
in
the vacuum-packaged CSS during storage at 4 °C for up to 6 weeks (Ye et al.
2008
).
The addition of nisin allowed a reduction in the concentration of sodium lactate from
4.5 mg/cm
2
(when tested singly) to 2.3 mg/cm
2
in the combination while achieving a
similar antilisterial effect at least during the fi rst 4 weeks of storage.
In another study, nisin and lysozyme (from hen egg and from oysters) were tested
on CSS stored at 4 °C (Datta et al.
2008
). The combinations of the two antimicrobi-
als were applied directly or in calcium alginate coating. The effectiveness of oyster
lysozyme or hen egg white lysozyme was enhanced when added incorporated onto
calcium alginate coatings. After 35 days at 4 °C the growth of
L. monocytogenes
and
Salmonella
Anatum was suppressed in the range of 2.2-2.8 log CFU/g with
nisin-lysozyme (from oysters as well as from hen egg) calcium alginate coatings
compared to the control nontreated samples, with no signifi cant differences from
the source of lysozyme. The study concluded that calcium alginate coatings con-
taining oyster lysozyme and nisin could be used to control the growth of
L. mono-
cytogenes
and
Salmonella
Anatum on the surface of ready-to-eat smoked salmon at
refrigerated temperatures.
Bacteriocins have been tested also in other ready-to-eat seafood products with the
purpose of enhancing shelf life or reducing the risk of
L. monocytogenes
. In smoked
salmon paté, results reported for nisin were not satisfactory compared to organic acid
salts of potassium sorbate and sodium lactate or sodium diacetate (Neetoo et al.
2008b
). Pâté samples supplemented with organic acid salt treatments had lower
counts by the end of 3 weeks compared to those incorporating nisin or nisin with
organic acid salts at a lower concentration. It was suggested that the ingredients in
pâté provided nisin protection for
L. monocytogenes
(Neetoo et al.
2008b
). In fi sh
spreads made from hake fl esh, enterocins 1071A and 1071B inhibited the growth of
aerobic mesophilic bacteria during cold storage (Dicks et al.
2006
). An enterocin
concentrate obtained by ammonium sulphate precipitation was added to the fi sh
spreads at 1.0 % (w/w), equivalent to 1.2×10
5
AU/g fi sh spread. The number of
microbial cells recorded in fi sh spread preserved with enterocins was 8 × 10
6
CFU/g
after 21 days of cold storage (4 °C), compared to 1 × 10
8
CFU/g in fi sh spread that had
not been preserved. Enterocins 1071A and 1071B did preserve the fi sh spread, but to
a lesser extent than a combination of sodium benzoate and potassium sorbate.
Cooked shelled crabmeat is prone to cross contamination with raw product by
personnel and from raw crab in the processing environment. Washing crabmeat with
antimicrobials (PerLac 1911, Microgard™, Alta™ 2341, nisin, or
Enterococcus
faecium
1083 culture supernatant containing the bacteriocin-like substance (BLIS)
enterocin 1083 reduced the viable counts of
L. monocytogenes
during storage at
4 °C only in the samples treated with 20,000 AU of Alta™ 2341, nisin, or enterocin
1083 (Degnan et al.
1994
). However, best results were reported for sodium diacetate
or trisodium phosphate. While trisodium phosphate considerably increased the pH
of crabmeat to unacceptable levels, sodium diacetate did not produce adverse effects
and reduced the levels of
L. monocytogenes
by 2.6 log units/g within 6 day.
Shucked lobster meat is prepared from lobsters cooked by immersion in boiling
water, cooled, and shucked by hand. The meat portions are packed with brine and
