Biomedical Engineering Reference
In-Depth Information
Chapter 6
Biopreservation of Egg Products
6.1
Application of Bacteriocins
A few studies have investigated the preservation of egg and egg products by applica-
tion of bacteriocins (Table
6.1
). The commercial use of liquid whole egg requires
processing in order to prolong its shelf-life and to inactivate foodborne pathogens.
As an alternative to conventional pasteurization, an ultrapasteurization processes
(i.e., heating at >60 °C for <3.5 min) was developed, which, when coupled with
aseptic processing and packaging, produced liquid whole egg with a shelf life of at
least 10 weeks at 4 °C. The use of effective aseptic fi lling and packaging systems (to
prevent postpasteurization contamination) remains an essential component in the
production of ultrapasteurized liquid whole egg with an extended pathogen-free
shelf life. Contrary to
Salmonella
, conventional minimal egg pasteurization pro-
cesses do not grant a complete inactivation of
Listeria monocytogenes
. As a matter
of fact,
Listeria
species can be isolated from commercially broken raw liquid whole
egg. Therefore, it was proposed to use bacteriocins for the control of
Listeria
in this
food system (Schuman and Sheldon
2003
). Addition of nisin to pasteurized liquid
whole egg reduced the viable counts of
L. monocytogenes
, increased the product
refrigerated shelf-life, and protected the liquid egg from growth of
L. monocyto-
genes
and
Bacillus cereus
during storage (Delves-Broughton et al.
1992
; Knight
et al.
1999
; Schuman and Sheldon
2003
). Nisin (200 IU/ml) extended the shelf life
of conventionally pasteurized liquid whole egg at 6 °C by 9 to 11 days relative to
nisin-free control samples (Delves-Broughton et al.
1992
). The addition of nisin
(1,000 IU/ml) to pH-adjusted ultrapasteurized liquid whole egg reduced
L. monocy-
togenes
populations by 1.6 to over 3.3 log CFU/ml and delayed (pH 7.5) or pre-
vented (pH 6.6) the growth of the pathogen for 8-12 weeks at 4 and 10 °C (Schuman
and Sheldon
2003
). Both nisin and pediocin PA-1/Ach acted synergistically with
heat treatments against
L. monocytogenes
(Knight et al.
1999
; Muriana
1996
). Nisin
added at 10 mg/l signifi cantly decreased the decimal reduction times (D-values) for
L. monocytogenes
in liquid whole egg. This effect was greater when the bacteriocin
