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.

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