Study of Ice Cream Freezing Process after Treatment with Ultrasound

World Applied Sciences Journal 4 (2): 188-190, 2008
ISSN 1818-4952
© IDOSI Publications, 2008
Study of Ice Cream Freezing Process after Treatment with Ultrasound
A. Mortazavi and F. Tabatabaie
Department of Food Science, Faculty of Agriculture,
Ferdowsi University of Mashhad, P.O. Box 91775-1163, Iran
Abstract: Application of power ultrasound to Food freezing is a relatively new subject, cavitations is the most
significant power which can not only lead to the production of gas bubbles in ice ream but also the occurrence
of micro streaming, also it can promote ice nucleation to accelerate the heat and mass transfer process
accompanying the freeze process. In this work ice cream freezing process time after treatment with ultrasound
(20 KHZ) was studied. Results were shown that ultrasound is beneficial power to ice cream freezing process
and it can be shorten the Freezing process time. Also be lead to product of better quality of ice cream e.g.
reducing crystal size and preventing incrustation of freezing surface.
Key word: Ice cream % freezing process % ultrasound
INTRODUCTION
is used to initiate nucleation in ice cream, it is suggested
that the power should be greater than 2 w cmG2 of liquid
Ice cream can be considered as an aerated
and the preferred frequency be 20 KHz. Further more, the
suspension of crystallized fat and water in highly
duration should be as short as possible and preferably no
concentrated sugar solution containing hydrocolloids,
more than 5 second [5]. In this study we have utilized from
casein micelles and proteins. The control of the
ultrasound power (20 KHz) for promoting of ice nucleation
crystallization process is one of the major factors affecting
and accelerate the heat and mass transfer process and
the stability and sensory characteristics of these
reduction time in freezing process. Also it be use to
products. Power ultrasound is a relatively new technology
provement of sensory characteristics such as flavor,
which can be used to promote the nucleation of ice [1]. In
texture and mouth feel in ice cream.
the presence of an acoustic wave, ice can be initiated at a
higher nucleation temperature, than under control
MATERIALS AND METHODS
conditions. The results from theoretical studies have
indicated that the cavitations bubbles produced by the
The first for the purpose of determining the effect of
ultrasonic wave are responsible for the nucleation process
power ultrasound during ice cream freezing process. One
[2]. Cavitations bubbles also benefit the freezing process
horn ultrasonic with frequency 20KHz and 5 levels of time
by reducing both the heat and mass transfer resistance at
(1, 5, 20, 40, 60 min) model Dr Hielscher, was used. also for
the ice/liquid interface and thus increasing freezing rate
ice cream manufacture a pasteurized, homogenized and
[3, 4]. Ice crystal is another major component of the
ripened standard ice cream mix were used and ice cream
freezing system, of ice cream than will fracture when they
consisted of 8% milk fat, 10% milk solids nonfat, 18%
are subjected to sound wave. Fragmentation of ice
sugar and 2.5% guar mixed were batch pasteurized at 75ºC
crystals leads to crystal size reduction [4]. Factors that
for 15 min and homogenized at 17.2 mpa first stage,
affect the efficiency of power ultrasound can be classified
3.4 mpa second stage. Cooled to 4°C and aged for 24h.
in two categories. Product factors and sound factors,
Then mix place into, Ice cream maker and, Ice cream frozen
product factors involve, parameters such as product
time investigate by determining of the nucleation forming
structure, moisture content and viscosity, initial gas
of ice crystals, Then determining of over run and
content and bubble size, etc., Sound factors include
characteristics properties in mix of ice cream. The
power and duration or pulse time of ultrasound,
statically analysis system was used an ANOVA to find
ultrasound frequency, ultrasonic mode. Power ultrasound
out effects of different levels pulse ultrasonic on the
Corresponding Author: Dr. F. Tabatabaie, Department of Food Science, Faculty of Agriculture, Ferdowsi University of
Mashhad, P.O.Box 91775-1163, Iran
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World Appl. Sci. J., 4 (2): 188-190, 2008
90
freezing time and quality characteristics of ice cream.
General linear model (P<0.05) was used to detect
86
differences among treatment means. All measurements
were performed in triplicate using three ice cream samples
) 82

(
%
per treatment.
n
e
r
r
u
v 78
O
RESULTS AND DISCUSSION
74
Figure 1 shows by increasing pulse time in all of
treatments, time freezing were decreased, observed
70
0 20 40 60
acoustic treatment of 1 min did not cause any significant
Pulse time (min)
change in freezing rate. The control sample
Fig. 2: Influence of pulse time on overrun
(non-ultrasound) had the highest time freezing 20 min
90
and all the other treatments had lower time freezing.
80
However noticeable increase of freezing was observed
70
)
when acoustic exposure time was raised to 5, 20, 40, 60
60

(
%
n 50
minute, further more, during the pulse time, changing
e
r
r
u
v 40
freezing period for ice cream with an acoustic exposure
O 30
time of 60minute was found to be the faster. Also the
20
samples prepared with 20, 40, 60 minute pulse time, had a
10
significantly (P = 0.05) lower time freezing than the others
0
Pulse time (min)
power ultrasound proposed to increase the initial gas
content so that the purporation of air lost due to the
Fig. 3: Influence of pulse time on overrun
ultrasound irradiation can be compensated or to carry out
2.6
Flavour
the process under increase pressure or to in corporate air
2.4
Texture
s
n
Mouth feel
2.2
into the partially frozen ice cream rather than at the initial
a
t
i
o
2.0
stage of the freezing process. Preventing incrustation on
a
l
u
1.8

e
v
the cold surface is another possible benefit effect [6],
r
y 1.6
s
o
Ultrasound can promote ice nucleation due to cavitations
e
n 1.4
S 1.2
and enhance heat and mass transfer due to microstreming
1.0
agitation [7].
0 10 20 30 40 50 60
Pulse time (min)
By increasing pulse time to 20 minutes, over run was
increased and then decreased (Fig 2). Over run in all
Fig. 4: Influence of pule time on sensory evaluations
treatments was higher than control sample, 73%, except
for produced sample with 1 minute pulse time, the results
showed that, pulse time had significant effect (P = 0.05) on
over run increasing (Fig. 3).
20
The negative effect of time power ultrasound on the
overrun can be minimized by applying 20 minuet of from
18
time power ultrasound. The lowest over run a bout 77%
)
observed for 60 min of pulse time, over run reduction for

(
°
C
16
g
ice cream treated for 60 minute was faster than 40 and
20 min, This might be due to the accumulated thermal
e

f
r
e
e
z
i
n
14
i
m
T
effect which is proportional to acoustic duration. Also
12
might high time power ultrasound can promote crystal
fragmentation in ice cream [8-12].
10
Between all treatments the sample prepared with
0 20 40 60
Pulse time of ultrasound (min)
20 minutes pulse time had the best sensory flavor, texture
and mouth feel evaluations (Fig. 4). Flavor and texture
Fig. 1: Influence of pulse time on time freezing
in control sample were better than the others but the
189

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World Appl. Sci. J., 4 (2): 188-190, 2008
samples prepared with 5 and 20 minutes pulse time had
5.
Chow, R.C.Y., R.A. Blindt, R.C. Chivers and
better mouth feel than the control.
M.J.W. Povey, 2004. A study on the primary and
Power ultrasound is known as a commercial method
secondary nucleation of ice by power ultrasound.
for degassing some liquid frozen manufacturing
Ultrasonic. In Press.
processes and thus can modification of the ice cream
6.
Chow, R.C.Y., R.A. Blindt, A. Kamp, P. Grocutt and
sensory characteristics. Such as texture and mouth feel.
R.C. Chivers, 2003a. Stimulation of ice crystallization
In summary these results showed that pulse time had
with ultrasonic cavitations-microscopic studies. Ind.
effective influence on decrease of time freezing and over
J. Phy., 77A: 315-318.
run increasing and sensory properties according to these
7.
Chow-McGarva, R.C.Y., 2004. A study on the
results the best treatment was the sample prepared with
sono crystallization of ice. Ph.D Submitted to the
20 minute, of pulse time. That decreased time freezing
University of Leeds.
about 35% in ice cream processing [12].
8.
Grout, B.W.W., J.M. Morris and M.R. Mclellan, 1991.
The freezing of fruits and vegetables. In Bald, W.B.
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