Effect of homogenization on some properties of sour cream


El-Nimr, A.A.; Szakaly, S.; Schaffer, B.

Egyptian Journal of Dairy Science 3(2): 104-112

1975


The effect of homogenization pressure and temperature on the properties of Sour Cream containing 16% fat was studied. Creamn was homogenized under pressures ranging from 50 to 110 Kg/cm2 at 45°C and 65°C respectively. Cream homogenized at lower temperatures, has slightly higher fat globule size, with appreciable increase in viscosity Than their counterparts homogenized at higher temperature. Electron, and phase contrast microscopy showed the presence of more fat agglomerates in cream homogenized at low temperatures, and that it increased with the increase in the pressure used in homogenization. Homogenization under a pressure of 80 kg/cm2 at 65°C gave Sour Cream with acceptable organoleptic, as well as cooking and physical properties.

EFFECT
OF
HOMOGENIZATION
ON
SOME
PROPERTIES
OF
SOUR
CREAM
By
A.
A.
EL-NIMR,*
S.
SZAKALY
and
B.
SCHAFFER
Hungarian
Dairy
Research
Institute,
Pecs,
Hungary
SUMMARY
The
effect
of
homogenization
pressure
and
temperature
on
the
properties
of
Sour
Cream
containing
16%
fat
was
studied.
Creamn
was
homogenized
under
pressures
ranging
from
50
to
110
Kg
/crn.
2
at
45°C
and
65°C
respectively.
Cream
homogenized
at
lower
temperatures,
has
slightly
higher
fat
globule
size,
with
appreciable
increase
in
viscosity
Th
an
their
counterparts
homogenized
at
higher
temperature.
Electron,
and
phase
contrast
microscopy
showed
the
presence
of
more
fat
agglomerates
in
cream
homogenized
at
low
,tem-
peratures,
and
that
it
increased
with
the
increase
in
the
pressure
used
in
homogenization.
Homogenization
under
a
pressure
of
80
kg/cm
2
at
65°C
gave
Sour
Cream
with
acceptable
organoleptic,
as
well
as
cooking
and
physical
properties.
INTRODUCTION
Sour
cream
is
one
of
the
import-
ant
dairy
products
in
Hungary,
as
it
widely
used
in
cooking
and
bakery.
Previous
reports
(Schrem
and
Obert,
1972),
showed
that
the
properties
of
Sour
Cream
was
greatly
affected
by
the
conditions
of
homogenization.
They
(Schrem
&
Obert,
1972)
report-
ed
that
homogenization
at
200-210
kg/cm
2
at
74
°C
gave
cream
with
the
best
consistancy,
however,
it
had
low
heat
stability.
Therefore,
the
present
study
was
undertaken
to
fi
nd
the
proper
homo-
genization
pressure
and
temperat-
ure
for
Sour
Cream
to
get
a
product
with
satisfactory
cooking
properties
as
well
as
other
physical
properties.
This
was
the
object
of
the
present
paper.
EXPERIMENTAL
PROCEDURE
Preparation
of
Sour
Cream':
Cream
was
standardized
to
16%
fat,
pasteurized
at
72°C
for
8-10
min.
and
then
cooled.
Cream
was
homogenized
using
a
single
stage
homogenizer
(
Soavi
B.
&
Figli
Z
*
Post
doctoral
Fellow,
National
Research
Centre,
Dokki,
Cairo,
Egypt.
Egyptian
J.
Dairy
Sci.
:
3
:
104-112.
4
d
4
1,5
1,5
1.0
as
EL-IIIIVIR
ET
AL.
45°C
65
°C
0
i0
10
JO
40
50
60
65
70
@0
90
95
too
IV
kgi
on
1
Fig.
(1)
Effect
of
homogeniztion
pressure
on
the
size
of
fat
globules
in
fresh
Cream.
57L)
with
pressures
varying
from
.
50-110
kg/cm
2
at
two
different
temperatures;
namely
45
and
65°C.
Cream
was
inoculated
with
2%
butter
culture,
incubated
at
24°
C
for
14-16h,
and
stored
in
the
ref-
rigerator
for
48h.
105
The
viscosity
of
cream
was
deter-
mined
at
20°C
using
viscosimeter
type
RN23.
The
size
of
fat
globules
was
measured
turbidimetrically
according
to
Vaitkus
and
Kaslaus
Kaite
(1969).
Five
-tenth
milliliter
of
cream
was
dilted
with
ml
of
0.3%
106
HOMOGENIZATION
EDTA
in
distilled
water
and
tested
for
fat
agglomeration
using
Mikro-
val-Lavoval
phase
cnotrast
micro-
scope
with
550
magnification
at
2
sec.
intervals.
The
structure
and
dispersion
of
fat
globules
in
Cream
was
examined
by
electron
microscopy
following
the
method
of
Henstra
and
Schmidt
(1970)
with
the
following
modific-
ations.
Cream
samples
were
fi
xed
with
2%
glutraldhyde
followed
by
1%
0s0
4
in
a
phosphate
buffer
of
pH
6.5
and
ionic
strength
0.05,
and
then
dehydrated
by
successive
immers-
ion
in
solutions
with
increasing
alcohol
concentrations
and
fi
nally
in
absolute
alcohol.
The
dehydrated
specimens
were
soaked
successively
in
solutions
of
equal
portions
of
propylene
oxide
and
absolute
alco-
hold
and
propylene
oxide
and
durc-
upan
each
for
15
min.
Finally,
the
specimens
were
embedded
in
durc-
upan
for
36
h.
at
60°
C.
Sections
(500
jt)
were
cut
using
LKB
ultramicrotome
type
4802,
and
stained
with
alkaline
lead
citrate
and
uranyl
acetate
and
then
examin-
ed
by
TESLA
BS613
electronmicro-
scope.
The
cooking
properties
of
crea
was
tested
by
mixing
10
ml
of
Sour
Cream
with
75
ml
of
boiling
distill-
ed
water
and
then
cooled
to
room
temperature.
Ten
melliliters
of
the
treated
cream
were
layered
in
a
petri-dish,
and
the
density
of
the
formed
fi
occulten
was
recorded;
the
more
curdled
properties
would
ind-
icate
inferior
cooking
properties.
The
Sour
Cream
was
judged
by
test
pannel
of
seven
experts
accord-
ing
to
the
Hungarian
Standards.
01:
.
SOUR
CREAM
RESULTS
AND
DISCUSSION
Fig.
1
shows
the
changes
in
the
fat
globule
size
as
affercted
by
the
pressure
and
temperature
of
hom-
ogenization.
It
is
obvious
from
the
attained
results
that
both
factors
greatly
affected
the
fat
globule
size.
Thus
unhomogenized
cream
had
an
average
fat
glouble
size
of
3.52
m
that
greatly
reduced
to
1.13
and
1.25
m
It
when
homogenized
using
a
pressure
of
50
kg/cm
2
at
65°
and
45°C
respectively.
The
average
fat
globule-
size
of
homogenized
cream
gradually
decreased
with
the
incr-
ease
in
the
pressure
used
reaching
0.53
m
t
and
72
m
It
in
cream
homog-
enized
under
pressure
of
110
kg/cm
2
at
65
and
45°C
respectivelly.
These
results
showed
that
the
higer
temperature
used;
namely
65°C,
improved
the
efficiency
of
homog-
enization,
probably
due
to
the
lower
viscosity
of
cream
at
the
higher
temperature.
Electron
micrographs
of
specimen
from
unhomogenized
cream,
homog-
enized
cream
under
a
pressure
of
80
kg/cm
2
at
45
and
65°C
are
shown
in
Fig.
2
a,
b
and
c
respectively.
With
unhomogenized
cream,
the
fat
globules
were
not
clearly
detect-
ed
due
to
the
saturated
character
of
milk
fat
to
0s0
4
and
the
low
thick-
ness
of
the
globule
membrane.
The
electron
micrographs
also
showed
casein
micelles
as
large
spherical
aggregates.
When
cream
was
homogenized
under
a
pressure
of
80
kg/cm
2
at
45°C
(Fig.
2b),
the
surface
of
the
fat
globules
were
surrounded
by
a
thin
osmophilic
layer
probably
def-
ormed
casien.
Besides
the
casien
aggregates
tended
to
be
smaller
than
in
unhomogenized
cream.
The
EL-NIMR
ET
AL.
107
Fig.
2
(a)
p
i•
zF
1
Fig.
2
(b)
108
HOMOGENIZATION
OF
SOUR
CREAM
40
Fig.
2
(c)
Fig.
(2)
Electron
micrographs
fat
globules
in
16%
fat
Cream;
(a)
without
homogenization
(b)
homogenized
at
45°C
under
80
Kg/Cm
2
,
(c)
homogenized
at
65
°C
under
80
Kg/Cm
2
,
fi
gure
also
showed
that
casein
acted
as
bridges
between
fat
globule
agg-
lumerates.
Henstra
and
Schmidt
(1970)
report-
ed
that
casein
miclles
tended
to
desintigrate
on
homogenization
being
in
accordance
with
the
pre-
sent
results.
Homogenization
of
Cream
at
65°C,
brought
more
protein
on
the
surface
of
fat
globules
(Fig.
2c).
On
account
of
the
thick
osrnophilic
layer
on
the
surface
of
fat
globules.
Besides
the
fat
globules
appeared
as
single
globules
or
as
agglomerates
of
few
fat
globules
in
comparison
to
cream
homogenized
at
45°C.
Results
attained
from
phase
cont-
rast
microscopy
showed
that
fat
globules
in
unhomogenized
cream
appeared
as
large
spherical
glob-
ules,
Fig.
3a,
while
that
of
homogen-
ized
cream
under
a
pressur
of
80kg/
cm
2
at
45°C
as
agglomerates
of
small
fat
globules
surrounded
by
a
thick
layer
of
casein,
Fig.
3b.
On
the
other
hand,
few
agglomerate
were
observ-
ed
in
cream
homogenized
at
65°C,
Fig.
3c.
These
results
add
to
the
conclusion
attained
from
electron
microscopy,
that
at
low
temperature
of
homogenization,
fat
globules
tended
to
agglomerate
at
different
pressure
used
and
fat
globule
agg-
lomerate
would
increase
with
the
EL
-
NIMR
70.,T
AL
1
OR
A
11.
Fig.
3
(a)
4*.
Fig.
3
(b)
110
HOMOGENIZATION
OF
SOUR
CREAM.
Fig.
3
(c)
Fig.
3.
Phase
Contrast
microscopy
of
Fat
globules
in
16%
Cream;
(a)
without
homogenization
(b)
homogenized
at
45°C
under
80
Kg/Cm
2
,
(c)
homogenized
at
65°C
under
80
Kg/Cm
2
,
increase
in
the
pressure
of
homog-
enization.
These
results
are
in
accordance
with
that
reported
by
Iverson
(1971)
using
ice
cream
mixes.
The
viscosity
of
=homogenized
cream
was
found
to
be
much
less
than
that
of
homogenized
cream.
Besides
the
viscosity
of
homogeniz-
ed
cream
gradually
increased
with
the
increase
in
the
pressure
used.
The
effect
of
homogenization
on
the
viscosity
of
cream
was
more
pro-
nounced
at
the
lower
temperature
namely
45°C,
Fig.
4.
Based
on
the
attained
results
from
electron
and
phase
contrast
microscopy,
one
could
say
that
differences
in
the
viscosity
with
temperature
of
homogenization
depends
largly
on
fat
globule
agg-
lomoeration
and
to
a
limited
extent
on
fat
globular
size.
Testing
the
cooking
properties
of
Sour
Cream
revealed
that
unhom-
ogenized
cream
gave
large
fl
occul-
ants
indicating
inferior
properties.
With
homogenized
cream,
the
best
cooking
properties
attained
with
cream
homogenized
using
a
pressure
of
80
kg/cm
2
at
65°C.
Organoleptic
scoring
of
the
differ-
ent
Sour
Cream
showed
that
Cream
homogenized
using
80kg/cm
2
at
65°C
ranked
the
highest
scoring
points
and
considered
as
the
best
cream
obtained.
From
the
previous
results
one
could
say
that
homogenization
of
Sour
Cream
using
a
pressure
of
80
kg/cm
2
at
65°C
resulted
in
a
product
of
good
Organoleptic,
cooking
as
well
as
other
physical
properties.
f40
itO
100
80
60
40
10
EL
-
NIMR
ET
AL.
111
45'c
65'c
Jo
65
ag
fif
;co
do
hrs
Fig,
(4)
Effect
of
homogenization
conditions
on
the
viscosity
of
Cream.
112
HOMOGENIZATION
OF
SOUR
CREAM.
REFERYNCES
Henstra,
S.
and
Schnidt,
D.
G.
(1970).
On
the
Structure
LI
the
Fat
-Protein
Complex
in
Homogenized
Cow's
Milk.
Neth.
Milk
Dairy,
J.
24
:
45.
Iversen,
E.
K.
(1971).
The
Importance
of
Homogenization
Ice
Cream
Quality.
Ice
Cream
and
Frozen
Confectionary,
July
1971.
Schrem,
J.,
and
Obert,
G.
(1972)
25th
KEKI
Scientific
Meeting,
Budapest,
Dee.
1972.
Vaitkus,
V.,
and
Kazlauskaite,
E.,
(1969).
Trudy
lett
FiliaL
Vses.
nauthno-
issled.
Inst.
maslodel'n
Syrodel'n
Prom.
4
:
157.
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