Biomedical Engineering Reference
In-Depth Information
Chapter 7
Biopreservation of Seafoods
7.1
Application of Bacteriocin Preparations
Listeria monocytogenes
is the main bacterial pathogen of concern in seafood prod-
ucts. One study found
L. monocytogenes
in ca. 30 % of smoked-fi sh samples,
although viable counts were below 100 CFU/g (Uyttendaele et al.
2009
). Another
study found populations of
L. monocytogenes
greater than 10
2
CFU/g in 2.6 % of
fresh fi sh, 5.1 % in smoked fi sh and 10 % in salted-fi sh purchased in fi sh farms,
while 20 % of smoked fi sh purchased in a fi sh market were also contaminated (Basti
et al.
2006
). The bacterium was also found in raw fi llets of catfi sh (23.5 %), trout
(5.7 %), tilapia (10.3 %), and salmon (10.6 %) (Pao et al.
2008
), or in 44.5 % of raw
freshwater fi sh tested (Yücel and Balci
2010
). Bacteriocin preparations have been
tested singly or in combination with other hurdles to control
L. monocytogenes
in
different types of seafoods (Table
7.1
).
7.1.1
Raw Seafoods
Inhibition of aerobic bacteria is important to prevent seafood spoilage. The combi-
nation of nisin and Microgard™ reduced the total bacterial counts and delayed
growth of
L. monocytogenes
in fresh-chilled salmon during 14 days at 6 °C, increas-
ing the product shelf life (Zuckerman and Ben Avraham
2002
; Calo-Mata et al.
2008
). The observed effect was explained by the inhibitory activity of Microgard™
on Gram-negative bacteria and nisin activity on Gram-positives. Inhibition of
L. monocytogenes
in fesh salmon was also considered to be relevant as a way of
preventing or reducing the levels of this bacterium in processed products such as
cold-smoked salmon. In another study, nisin (200 IU/g) added on fresh gilthead
seabream fi llets packed under modifi ed atmosphere was the most effective treatment
resulting in signifi cant shelf life extension of fi llets (48 days compared to 10 days
