Inhibition of Listeria monocytogenes during cheese manufacture by adding nisin to milk and/or using a nisin-producing starter


Richard, J.

Food Ingredients Europe Conference Proceedings, Porte de Versailles, Paris 4, 5, 6 October 1993: 58-64

1993


A model system using tryptic soy broth (Difco) + 0.6% yeast extract as culture medium and non-pathogenic Listeria innocua as test organism, was developed for studying the anti-listerial activity of low nisin concn, and the combined effect on it of pH and temp. Irrespective of nisin concn up to 200 IU/ml, pH of medium or temp. of incubation, addition of nisin was followed by a rapid drop in listeria count. Results are reported of pilot-scale studies on the manufacture of Camembert cheese from pasteurized milk that had been artificially contaminated with L. monocytogenes VT, using nisin-producing (Nis+) and nisin-negative strs of Lactococcus lactis var. lactis as starter. The listeria count decreased during the 1st 24 h in cheese made with Nis+ starter, but regrowth of listeria occurred in all cheeses as the pH increased, and was observed sooner in the crust than in the core of the cheese. Addition of small amounts of nisin to the cheese milk, either with or without heat treatment, combined with the use of Nis+starter, considerably improved the anti-listerial effect.

1118
Report
and
Abstracts
Inhibition
of
Listeria
monocytogenes
during
cheese
manufacture
by
adding
nisin
to
milk
and/or
using
a
nisin-producing
starter.
J.
Richard
(INRA,
Station
de
Recherches
Laitieres,
F-78352
Jouy-en-Josas
Cedex,
France).
First,
the
results
of
a
study
on
the
anti-listerial
activity
of
low
nisin
concentrations
are
presented,
using
as
a
model
a
culture
medium
and
a
non-pathogenic
organism,
Listeria
innocua.
Addition
of
nisin
to
the
medium
caused
a
rapid
drop
in
cell
viability
followed
by
the
regrowth
of
the
survivors
at
the
same
rate
as
the
control
culture.
The
maximum
decrease
in
population
(L
,,ax)
was
used
to
study
the
combined
effect
of
pH
and
temperature
on
the
anti-listerial
activity
of
nisin.
Camembert
cheese
was
made
in
our
pilot
plant
using
pasteurized
milk
artificially
contaminated
with
Listeria
monocytogenes.
A
nisin-producing
strain
of
Lactococcus
lactis
subsp.
lactis
was
used
in
comparison
with
a
nisin-negative
strain
of
the
same
species.
The
nisin
concentration
in
milk
and
curd
paralleled
the
lactococcal
growth,
with
a
maximum
of
c.
700
IU/g
in
curd
at
9
hr.
The
nisin
concentration
then
slowly
decreased
in
the
cheese
core,
whereas
a
dramatic
drop
occurred
in
the
crust
during
the
1st
week
of
ripening.
During
the
first
24
hr
of
manufacture
the
number
of
listeria
decreased
in
cheese
containing
the
nisin-producing
starter,
whereas
it
slowly
increased
in
the
control.
During
the
1st
week
of
ripening,
the
number
of
listeria
remained
almost
unchanged
in
both
kinds
of
cheese,
despite
the
presence
of
at
least
200
IU/g
of
residual
nisin
in
the
experimental
ones.
Whatever
starter
was
used,
regrowth
of
the
listeria
occurred
when
the
pH
increased,
i.e.
sooner
in
the
crust
than
in
the
core.
However,
the
mean
difference
of
2.4
log
unit
cfu/g
in
listeria
counts
in
cheese
aged
1
day
was
maintained
throughout
the
6
weeks
of
ripening.
Further
study
showed
that
nisin
adsorption
at
low
pH
on
to
certain
milk
component(s),
different
from
fat,
accounts
for
the
loss
of
activity
of
the
compound
after
cheese-making.
Addition
of
small
amounts
of
nisin
to
milk,
associated
or
not
associated
with
heat
treatment
at
sublethal
temperatures,
in
combination
with
the
use
of
a
nisin-producing
starter,
improved
the
anti-listerial
activity
of
this
substance.
Treatment
of
envenoming:
the
need
for
improved
antitoxins
and
ancillary
pharmacological
agents.
D.
A.
Warrell
(Centre
for
Tropical
Medicine,
University
of
Oxford,
John
Radcliffe
Hospital,
Headington,
Oxford
OX3
9DU,
U.K.).
Each
year,
50,000-100,000
people
die
of
snakebite
and
about
5000
of
scorpion
stings.
The
most
frequent
causes
of
death
after
snakebite
are
respiratory
paralysis
(Elapidae)
and
intracranial
and
other
types
of
haemorrhage,
shock
and
renal
failure
(Viperidae).
Persisting
morbidity
results
from
local
necrosis.
Deaths
after
scorpion
envenoming
are
usually
due
to
myocardial
failure
and
pulmonary
oedema.
In
snakebite
victims,
traditional
F(ab)
2
antivenoms
are
effective
in
reversing
haemostatic
and
cardiovascular
disturbance
and
postsynaptic
neurotoxicity,
but
are
less
effective
against
cytotoxicity,
presynaptic
neurotoxicity,
generalized
rhabdomyolysis
and
acute
renal
tubular
necrosis.
In
scorpion
envenoming
the
use
of
antivenom
is
more
controversial:
in
North
Africa
and
Brazil
physicians
use
antivenoms,
whereas
in
Israel
and
India
they
do
not.
Innovations
in
antivenom
production,
such
as
immunization
of
animals
with
venom
fractions
or
purified
toxins
and
the
use
of
monoclonal
antibodies,
have
been
discouraged
by
their
cost.
Recently,
Fab
fragment
antivenoms
(like
Digibine
)
have
been
prepared
and,
in
some
cases,
specific
Fab
was
purified
by
affinity
chromatography.
Fab
fragments
have
the
theoretical
advantage
of
more
rapid
distribution
and
a
larger
apparent
volume
of
distribution
ensuring
neutralization
of
the
venom
depot
at
the
site
of
inoculation.
Elimination
of
complement
Fc
fragments
will
reduce
the
risk
of
early
antivenom
reactions.
Improved
affinity
of
antivenoms
and
increased
antivenom
concentration
in
the
region
of
the
tissue
acceptor
may
reverse
the
binding
V
:TA(----)
in
the
following:
V:TA,=-
TA
+
V
V
+
AV±V:AV,
where
V
=
venom;
TA
=
tissue
acceptor;
AV
=
antivenom.
Ancillary
pharmacological
methods,
such
as
anti-
cholinesterases
and
3,4-diaminopyridine
in
neurotoxic
snakebites
and
vasodilators
in
victims
of
scorpion
stings,
may
complement
the
use
of
antivenoms.
There
is
increasing
interest
in
studying
the
mechanisms
by
which
venomous
animals
and
their
predators
avoid
envenoming.
Maitotoxin
action
on
fibroblastic
cells
along
the
cell
division
cycle.
M.
Ammar,'
J.
Berreur-Bonnenfant,'
A.
Dubreuil,
3
H.
Kiefer,'
G.
Diogene,
2
P.
Metezeau
4
and
S.
Puiseux-Dao
2
('
CEMATMA,
Universite
Paris
7,
2
Place
Jussieu,
75251
Paris
Cedex
05,
France;
2
ECMR,
CNRA
URA
1449,
4
Place
Jussieu,
75257
Paris
Cedex
05,
France;
3
INSERM
U303,
1
Avenue
Jean
Lorrain,
06000
Nice,
France;
4
Biochimie
Cellulaire
et
Cytometrie
Analytique
et
Preparative,
SC
9
INSERM-Pasteur,
28
Rue
du
Dr
Roux,
75724
Paris
Cedex
15,
France).
Maitotoxin
(MTX)
induces
an
increase
of
Ca.+
and
phosphoinositide
breakdown
in
various
cell
types,
The
Ca;"
increase
followed
with
fluorescent
probes
on
cell
suspensions
has
been
described
as
slow
and
lasting,
different
from
the
'signal'
induced
by
calcium
ionophores
such
as
ionomycin.
MTX
effects
have
been
studied
on
two
synchronized
fibroblastic
cell
lines,
BHK21
C13
and
FR
3T3.
In
BHK21
C13
cells,
flow
cytometry
analysis