Biomedical Engineering Reference
In-Depth Information
nential growth of the pathogen during further storage of samples (Iseppi et al.
2008
).
Marcos et al. (
2007
) tested the antilisterial effects of enterocins A and B immobi-
lized in different supports (alignate, zein and polyvinyl alcohol) on air-packed and
vacuum-packed sliced cooked ham stored at 6 °C. The most effective treatment for
controlling
L. monocytogenes
during storage was vacuum-packaging of ham with
alginate fi lms containing 2,000 AU/cm
2
of enterocins, with no increase from inocu-
lated levels of
L. monocytogenes
until day 15.
Pre-surface application of bacteriocins in combination with post-packaging treat-
ments is another approach of recent interest. Bacteriocin application followed by
in-package thermal treatments can provide an effective combination to control
L. monocytogenes
on products such as frankfurters or turkey bologna, as shown for
pediocin, nisin, nisin-lysozyme, or combinations of these bacteriocins with sodium
lactate/sodium diacetate (Chen et al.
2004a
; Mangalassary et al.
2008
). Mangalassary
et al. (
2008
) studied the effi cacy of in-package pasteurization (65 °C for 32 s.) com-
bined with pre-surface application of nisin and/or lysozyme to reduce and prevent
the subsequent recovery and growth of
L. monocytogenes
during refrigerated stor-
age on the surface of low-fat turkey bologna. In-package pasteurization in combina-
tion with nisin or nisin-lysozyme treatments was effective in reducing the population
below detectable levels by 2-3 weeks of storage. In bologna manufactured with
different sodium lactate/sodium diacetate combinations, dipping in pediocin solu-
tion followed by heat treatment decreased the
D
-values for inactivation of
L. mono-
cytogenes
at low pediocin concentration, but exhibited a protective effect at higher
concentrations, indicating that interactions between additives in formulations can
vary at different temperatures/concentrations (Maks et al.
2010
). In a previous study,
treatments of frankfurters with 3,000 AU or 6,000 AU pediocin (in ALTA 2341) fol-
lowed by heating in hot water reduced the populations of inoculated
Listeria
in
proportion to the intensity of treatments (Chen et al.
2004a
). The combination of
pediocin (6,000 AU) with post-packaging thermal treatment (81 °C or more for at
least 60 s), achieved a 50 % reduction of initial inoculation levels. Little or no
growth of
L. monocytogenes
was observed on the treated frankfurters for 12 weeks
at 4 or 10 °C, and for 12 days at 25 °C. This treatment did not affect the sensory
qualities of frankfurters. The authors of this study concluded that pediocin (in ALTA
2341) in combination with postpackaging thermal treatment offers an effective
treatment combination for improved control of
L. monocytogenes
on frankfurters.
Another example of a combined treatment is the application of nisin with pulsed
light. Application of a Nisaplin dip followed by exposure to pulsed light (PL; 9.4 J/
cm
2
) reduced the population of
L. innocua
on sausages by 4 log cycles and inhibited
its growth during refrigeration storage for 24-48 days (Uesugi and Moraru
2009
).
Since application of PL is approved for decontamination of food and food surfaces,
the combined treatment could be applied as a post-processing step to reduce surface
contamination and increase the safety of RTE meat products.
Bacteriocins have been proposed for use in packaged foods to increase the effi -
cacy of irradiation treatments. One study reported that irradiation acted synergisti-
cally with pediocin on
L. monocytogenes
inoculated in packaged frankfurters
(Chen et al.
2004b
). Combination of pediocin with postpackaging irradiation at
