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Food
Research
and
Development
Centre,
Agriculture
and
Agri-food
Canada,
St.
Hyacinthe,
Quebec,
Canada
J2S
8E3.
Tel.
450-773-1105.
Fax
450-8461.
E-mail
farnworthed@agr.gc.ca
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Abstract
Kefir
is a
fermented
milk
drink
produced
by the
actions
of bacteria
and
yeasts
contained
in kefir
grains,
and
is reported
to have
a unique
taste
and
unique
properties.
During
fermentation,
peptides
and
exopolysaccharides
are
formed
that
have
been
shown
to have
bioactive
properties.
Moreover,
in vitro
and
animal
trials
have
shown
kefir
and
its
constituents
to have
anticarcinogenic,
antimutagenic,
antiviral
and
antifungal
properties.
Although
kefir
has
been
produced
and
consumed
in Eastern
Europe
for
a long
period
of time,
few
clinical
trials
are
found
in the
scientific
literature
to support
the
health
claims
attributed
to kefir.
The
large
number
of microorganisms
in kefir,
the
variety
of possible
bioactive
compounds
that
could
be formed
during
fermentation,
and
the
long
list
of reputed
benefits
of eating
kefir
make
this
fermented
dairy
product
a complex
probiotic.
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Hydrogen
peroxide
is another
metabolite
produced
by some
bacteria
as an
antimicrobial
compound.
Yu¨ksekdag˘
et al.
(2004a)
showed
that
all
21 isolates
of lactic
acid
bacteria
from
Turkish
kefir
produced
hydrogen
peroxide
(0.04–0.19
ug/ml).
In a
later
paper,
they
reported
that
11 out
of 21
strains
of kefir
lactococci
produced
hydrogen
peroxide
(Yu¨ksekdag˘
et al.
2004b).
All
lactococci
strains
were
effective
in inhibiting
growth
of Streptococcus
aureus,
but
were
less
effective
against
E. coli
NRLL
B-704
and
Pseudomonas
aeruginosa.
Several
hypotheses
have
been
proposed
regarding
the
possible
mechanism
of action
employed
by bacteria
to reduce
cholesterol
levels
(St.
Onge
et al.
2002).
Vujicic
et al.
(1992)
showed
that
kefir
grains
from
Yugoslavia,
Hungary
and
the
Caucase
region
were
able
to assimilate
cholesterol
in milk
either
incubated
at 208C
for
24 h
(reductions
of up
to 62%)
or incubated
and
stored
at 108C
for
48 h
(reductions
of up
to 84%).
These
authors
claimed that
their
results
indicated
that
kefir
grains
had
a cholesterol-
degrading
enzyme
system.
Similar
results
were
reported
for
27 lactic
acid
bacterial
strains.
However,
it was
pointed
out
that
isolates
from
dairy
products
had
lower
cholesterol-assimilating
capacity
than
strains
isolated
from
infant
faeces
(Xanthopoulos
et al.
1998).
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10.6
Kefir
and
cholesterol
metabolism
Positive
effects
of yoghurt
consumption
on cholesterol
metabolism
have
been
reported
(Kiessling
et al.
2002;
Xiao
et al.
2003),
although
a review
of the
literature
reveals
that
the
results
are
at best
moderate,
and
are
often
inconsistent
(Taylor
and
Williams
1998;
St-Onge
et al.
2000;
Pereira
and
Gibson
2002).
found
in kefir.
Furthermore,
there
is evidence
to show
that
kefir
consumption
not
only
affects
digestion,
but
also
influences
metabolism
and
immune
function
in humans.
12.
References
Abraham,
A.G.
and
De Antoni,
G.L.
1999.
Characterization
of kefir
grains
grown
in cows’
milk
and
in soya
milk.
Journal
of Dairy
Research
66:
327-333.
Alm,
L. 1982a.
Effect
of fermentation
on lactose,
glucose,
and
galactose
content
in milk
and
suitability
of fermented
milk
products
for
lactose
intolerant
individuals.
Journal
of Dairy
Science
65:
346-352.
Alm,
L. 1982b.
Effect
of fermentation
on B-vitamin
content
of milk
in Sweden.
Journal
of Dairy
Science
65:
353-359.
Alm,
L. 1982c.
Effects
of fermentation
on curd
size
and
digest
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