_
Food Science and Technology Research, 20 (5), 987 996, 2014
Copyright © 2014, Japanese Society for Food Science and Technology
doi: 10.3136/fstr.20.987
http://www.jsfst.or.jp
Original paper
Effect of Vegetable Milks on the Physical and Rheological Properties of Ice Cream
Fatemeh Aboulfazli1*, Ahmad Salihin Baba1 and Misni Misran2
1
Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia
2
Received January 7, 2014 ; Accepted June 26, 2014
The nutritional properties and health benefits of ice cream can be improved by substituting cow’s milk with
vegetable milks. In the present study cow’s milk in ice cream was replaced by soy, coconut and composite milk
(combinations of coconut or cow milks with soy milk). The changes in ice cream eating qualities and physical
properties (melting rate, apparent viscosity, hysteresis, fat globule size and its zeta potential and freezing behavior)
were evaluated. The use of vegetable milk to replace cow milk increased pH and decreased melting rate. Ice
creams containing composite milk have reduced the melting rate, freezable water amount, particle size and total
acceptability of ice creams whereas increased viscosity and hysteresis area with increasing soy milk content. The
vegetable milks as composite milk can use to replace cow milk without markedly affecting the quality of ice cream.
Keywords: ice cream, soy milk, cow milk, coconut milk, physical properties
Introduction
Wide use of these two vegetable milks in food preparation can
The demand for alternatives to cow’s milk in ice cream making
be associated with the vegetable proteins favorable effects on
is growing due to problems associated with its fat, cholesterol and
improving physical properties of foods. For instance, the viscosity,
lactose (allergenicity) contents and increasing desire for vegetable
melting time and hardness of ice cream samples increased by
milk based ice cream. Soy milk is regarded as a suitable choice
substituting of skimmed milk powder with soy protein isolate
(Abdullah et al., 2003) because of its high nutritional quality
(Akesowan, 2009). The fortification of yogurt ice cream with soy
especially with respect to protein content and balance amino acids
protein improve the texture, firmness and viscosity of the product
(Gandhi et al., 2001). Frequent consumption of soy products offers
(Mahdian et al., 2012). Samoto et al. (2007) noted soy lecithin acts
health benefit such as lowering the risk of getting cancers, diseases
as emulsifier and also helps increase the viscosity, stability, texture
associated with cardiovascular, hypercholesterolemia, diabetes,
and extends the melting time of the ice cream. Abdullah et al.
bone and kidney (Dervisoglu et al., 2005). Coconut (Cocos
(2003) improved the quality of ice cream by using different ratios
nucifera) milk is another vegetable milk that may be used to
of skim milk in soy milk blend and found that large quantity of
replace cow milk. This milk is easy to digest and it contains an
skim milk with soy milk reduces the beany flavor of soy beans and
abundance of minerals (particularly calcium, phosphorus and
increased the quality of ice cream. Limited numbers of studies have
potassium) and vitamins (B, C and E vitamins) and antioxidant
been carried out on the use of coconut milk to replace cow milk in
activities. The high oleic and lauric acid content in coconut milk
ice cream. In order to attempt this, Kerdchouaym and Surapat
help in preventing arteriosclerosis and related illness. Coconut milk
(2008) improved the physical properties of low fat coconut milk
is commonly used by confectioners, bakeries, biscuits and ice
ice cream by replacing skim milk powder with whey protein
cream industries to enhance flavor and taste of various products
concentrate and it has increased ice cream mix viscosity and
(Belewu and Belewu, 2007).
reduced melting rate of ice cream. Vegetable milks has also
*To whom correspondence should be addressed.
E-mail: [email protected]
F. Aboulfazli et al.
988
reported to improve nutritional content of ice cream. For example,
Bisla et al. (2011) showed increased in expressed protein, fat, iron,
immediately chilling (4℃) prior to making ice cream.
Preparation of coconut milk
The brown hard coconut shell
vitamin C values and overall acceptability of the ice creams in
was cracked open and the white copra was grated followed by
comparison to standard cow’s milk ice cream by the using soy
mechanical pressing to obtain the milk. To achieve 8% fat coconut
milk, watermelon seeds milk and guava pulp.
milk, 300 g of fresh coconut milk (after sieving with double layers
The main challenge in using coconut or soy milk in ice cream
of cheesecloth) was mixed with 700 g of distilled water. The
is to obtain a stable colloidal system. For example lecithin in the
diluted coconut milk was heated at 80℃ for 10 min prior to
soy milk is responsible for the formation of hard ice cream
chilling (4℃) and was used within 1 h.
resulting in the requirement of about 15 minutes of standing at
Preparation of ice cream
Ice cream was prepared by using
room temperature to soften before serving (Wangcharoen, 2012). It
various combinations of coconut or cow milks with soy milk. To
is important to establish the extent of improvement in the physical
achieve ice creams with 43% total solids and 10.5% fat for a total
properties of ice cream as a result of adding coconut or soy milks.
batch of 100 g, ice cream mixes were prepared using formula as
Thus, the aims of this study were to determine the chemical,
shown in Table 1. The milk or milk combinations with butter were
physical and sensory properties of the ice creams when cow’s milk
heated to 50℃ prior to mixing with the skim milk powder, sugar
is partially replaced by coconut or soy milk.
and water. This was followed by two stages homogenization
(16000 rpm, 70℃, 5 min; Ika Homogenizer T-25 basic Ultra
Materials and Methods
Materials
Turrax, Germany). The mixtures were pasteurized (80℃ for 10 min
Fresh cow milk, coconut, soybean, soy oil, butter
in a water bath) followed by cooling to 4℃ and aging overnight at
and skim milk powder (Dutch lady, Malaysia), sugar and vanilla
4℃. The ice creams were then frozen in a 1.5 L batch ice cream
were purchased from local grocery. Cremodan SE 734 veg
maker (Baumatic gelato1ss, UK) and packed in 100 mL pre-
(Danisco AS, Copenhagen, Denmark, containing mono- and
sterilized plastic cups. The cups were then covered using the lids
diacyl-glycerols of fatty acid, cellulose gum, guar gum,
prior to freezing at −20℃. Three separate batches of ice cream
carrageenan) was used as stabilizers.
were prepared for each treatment.
Preparation of soy milk
Soybeans (10 g) were washed three
Chemical analysis
The pH of ice cream were measured using
times using tap water, one time rinsing using de-ionized water,
digital pH meter whereas titratable acid (TA) was determined by
followed by soaking in de-ionized water (1 L) for 14 h at room
titrating samples (10 g) with sodium hydroxide (0.1 N), using
temperature. Excess water was then drained off and the shells were
phenolphthalein as an indicator. The total solids were measured by
removed. The swollen beans were blended with 250 mL of boiling
drying samples at 100 ± 1℃ for 3.5 h using an air oven (Akin et
water in a laboratory blender (Waring, New Hartford, CT, USA) at
al., 2007). Fat content was calculated by weight after alkaline
low speed followed by boiling for 5 min. The blended soybean was
hydrolysis coupled with soxhlent extraction (petroleum ether)
then passed through 4 layers of cheesecloth. The soy milk fat
(AOAC, 2005). All measurements were performed three times.
content (1.86%) was corrected to 3.4% using 1.54 g soy oil/100 g
soy milk. The soy milk was reheated to 80℃ for 10 min and
Melting rate
The ice cream melting rate was determined as
described by Mahdian et al. (2012). Tempered ice cream samples
Table 1 . The content of components used in ice cream mix formulations (percentage by weight)
Ingredient
A
Sample
W
C
S
SW1
SW2
SW3
SC1
SC2
SC3
A
Milk formula Butter (%)
(%)
(Fat = 83 . 3%)
55 . 4
55 . 4
55 . 4
55 . 4
55 . 4
55 . 4
55 . 4
55 . 4
55 . 4
10 . 37
7 . 31
10 . 37
10 . 37
10 . 37
10 . 37
9.6
8 . 84
8 . 08
Skim milk
powder (%)
Sugar (%)
7
7
7
7
7
7
7
7
7
17
17
17
17
17
17
17
17
17
Stabilizer–
Vanillin (%)
Emulsifier (%)
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
Water (%)
9 . 62
9 . 62
9 . 62
9 . 62
9 . 62
9 . 62
9 . 62
9 . 62
9 . 62
W: ice cream with 100% cow milk; C: ice cream with 100% coconut milk; S: ice cream with 100% soy milk; SW1: ice cream
with 75% soy+25%cow milk; SW2: ice cream with 50% soy+50% cow milk; SW3: ice cream with 25% soy+75%cow milk;
SC1: ice cream with 75% soy+25% coconut milk; SC2: ice cream with 50% soy+50% coconut milk; SC3: ice cream with 25%
soy+75% coconut milk .
Physical Properties of Vegetable Milk Ice Cream
989
(spherical shape, _ 20℃, 30 g) were prepared by scraping the
Differential scanning calorimetry (DSC) of ice cream
The
surface of ice cream using a stainless steel table spoon and these
thermal properties of ice cream mixes (after aging step) were
were placed on a 0.2 cm wire mesh screen above a beaker at room
measured by a differential scanning calorimeter (DSC) by Mettler
temperature (25℃). The weight of the melted material was
Toledo (model DSC822e) according to the method reported by
measured after 20 min and declared as percentage weight melted.
Hwang et al. (2009). Sample of ice cream mixes (about 5 mg) was
Rheological measurements
Rheological measurements of
placed in a pre-weighed aluminum sample pan and the pan was
melted ice cream samples were determined using a Physica MCR
301 rheometer (Anton-Paar GmbH, Graz, Austria) with a
sealed using a Quick Press pan crimper (Perkin Elmer) and the
thermal data were recorded from _ 30℃ to +30℃ in nitrogen
concentric cylinder geometry coupled with a circulating cooling
atmosphere with a heating rate of 5℃ min . An empty pan served
bath at 4.0 ± 0.1℃ (Rossa et al., 2012). Melted ice creams (around
as the reference. The flow rates of nitrogen gas for cooling and
20 g) were left to equilibrate at 4.0℃ for 15 min. The samples flow
heating were 110 and 40 cc/min, respectively.
_
1
behavior was generated by linearly increasing the shear rate from
The onset temperatures (T0), peak temperatures (Tp), freezing
19.6 to 67.3 s−1 in 20 min followed by returning to 19.6 s−1 over a
points (Tf) and enthalpies (ΔHf) of the transitions of ice formation
further 20 min.
and ice melting were recorded. The onset temperatures are
The hysteresis of ice creams was evaluated by calculating the
area between the shear stress/shear rate curves.
considered as the intersection of the tangent and base line to the
left side of the melting peak. Freezing points were calculated by
The consistency index and the flow behavior were explained by
determining the temperature at which the steepest slope was
the Power Law model (Eq.1). Apparent viscosity of ice creams was
observed (the temperature at maximum slope of the endotherm or
estimated as a function of time under a constant shear rate of 20 s−1.
the extra-plotted peak onset temperature (T0) of the ice melting
σ = K (γ)n
(point Tf in Fig.1; Rahman, 2008)). The enthalpy of the phase
······Eq. 1
transition (ΔH f = enthalpy of fusion) was determined by
n
Where: σ is the shear stress (Pa); K = consistency index (Pa s );
extrapolating the baseline under the peak by connecting the flat
γ = the shear rate (s−1); and n = the flow behavior index (Rossa et
baseline before and after the melting peak and integrating the peak
al., 2012).
above the baseline, as indicated in Fig. 1. The amount of ice
Size and zeta potential
The average particle size and zeta
formed per gram of sample (freezable water) was determined by
potential of fat globules of ice cream mixes were determined by
integrating the melting curves and dividing the melting enthalpy
using Zetasizer ZS (Malvern Instruments, UK) at a constant
with the pure ice fusion latent heat (S = 334 J g 1) (Soukoulis et al.,
temperature of 25℃. Measurements were carried out with the
2009).
dilution of the ice cream mixes approximately 1:10000 with
_
Sensory analysis
The ice creams were organoleptically
deionized water. The zeta potential and size of ice cream mixes
evaluated by sixteen untrained panelists (25-30 year; 8 males, 8
were monitored after aging step (Tan and Misran, 2012).
females), using a sensory rating scale of 1-10 for taste and flavor,
Optical polarizing microscope imaging (OPM)
The OPM
and 1-5 for consistency and 1-5 for appearance and color (Akin et
micrographs of the ice cream mixes (after aging step) were
al., 2007). The properties evaluated contained (a) three
obtained using a Leica Polarizing Microscope equipped with a
characteristics for appearance and color (no criticism: 5, dull color:
Leica QWin software. All measurements were carried out at room
4-1, unnatural color: 3-1), (b) seven properties for taste and flavor
temperature (25℃) (Tan and Misran, 2012).
(no criticism: 10, cooked flavor: 9-7, lack of sweetness and too
Fig. 1. A typical DSC thermogram to determine the freezing point and ΔHf of ice cream.
F. Aboulfazli et al.
990
sweet: 9-7, lack of flavor: 8-6, rancid and oxidized:6-1, and other:
explained that soy milk proteins is more hydrated and therefore
5-1) and (c) seven terms describing texture and body (no criticism:
prevent their free movement of water molecules associated with
5, coarse: 4-1, crumbly: 4-2, weak: 4-1, fluffy: 3-1, gummy: 4-1,
proteins (Akesowan, 2009) which lead to reduced syneresis and
sandy: 2-1).
increased viscosity (Table 3). The relationship between the increase
Statistics The experiments were assayed in triplicates and the
in viscosity and increase in the resistance of ice cream to melting
results were expressed as mean ± S.E.M (standard mean error)
rate also reported by Kaya and Tekin (2001), Akesowan (2009) and
values. The statistical analysis was carried out using SAS statistical
Hermanto and Masdiana (2011). In addition the emulsifying
software, version 6.12 edition (SAS, 1996) followed by Duncan’s
properties of soy lecithin which provides protection for the
multiple range method for mean comparison. The criterion for
membrane proteins against damage due to freezing (Samoto et al.,
statistical significance was p < 0.05 (Homayouni et al., 2008).
2007) and assists good air distribution and fat structure in the ice
cream, also can affect on the increase of the time of melting of the
Result and Discussion
ice cream (Hermanto and Masdiana, 2011).
Compositions and physicochemical properties of ice cream
Ice creams containing cow milk had a higher melting rate than
The compositions and physicochemical properties of the ice creams
ice creams containing coconut milk. Melting rate can be influenced
are presented in Table 2. The total solid, fat and titratable acidity
by the differences in freezing points and viscosity of recipes (Salem
(TA) were unchanged by partial replacement of cow milk with soy
et al., 2005). However, in the present study no differences
or coconut milks. However, pH and melting rate changed with milk
( p > 0.05) were observed in the freezing points amongst ice creams
replacement. The pH was found to be the highest in ice creams
containing composite milk (Table 6). However they have
with C and SC3 ice creams and the lowest in W ice cream. Ice
noticeable differences in freezable water and the enthalpy of fusion
creams showed different melting behavior as a function of milk
(Table 6) due to their kind of proteins and their hydration tendency
replacement. While the content of butter used to balance to fat
(Alvarez et al., 2005) which affect on serum concentration and
(10.5%) were less in coconut ice cream (7.31 g vs. 10.37 g for ice
freezable water in the ice creams, hence their fusion enthalpies. Ice
creams containing cow and ice cream with 100% soy milk), this is
crystallisation is strongly dependent on the extent of freezing point
regarded to have minor effect on melting behavior. Hyvoen et al.
and the percentage of bound water (unfrozen water) (Soukoulis et
(2003) for instance reported that different types of fat (dairy and
al., 2009). Whey protein and casein isolates have a higher amount
vegetable fats) had no significant effect on perceived melting of ice
of aspartic and glutamic acids (negative charge) than coconut
creams, although fat amount did affect melting rate of ice creams.
All vegetables and composite milk ice creams (16.27 _ 33.36%)
protein, as well as a higher proportion of lysine and arginine
showed a slower melting rate than W ice cream (35.88%). The
protein than in coconut protein whereas the surface activity is said
melting rate decreased with increasing soy milk content in ice
to be higher in whey protein than in coconut protein (Onsaard et
creams containing composite milk and this presumably can be
al., 2006). The coconut proteins are generally known for having
(positive charge). The value of zeta potential is higher in whey
Table 2 . Composition and physico-chemical properties of experimental ice creams
Composition
SamplesA
W
C
S
SW1
SW2
SW3
SC1
SC2
SC3
A
Physico-chemical properties
Total solids
(g/100g)B
Fat
(g/100g)B
pH
(value)B
Titratable acidity
(%lactic acid)B
Melting rate (% ice
cream melted after
15 min)B
43 . 91 ± 0 . 08a
43 . 16 ± 0 . 07a
43 . 94 ± 0 . 08a
43 . 23 ± 0 . 15a
43 . 42 ± 0 . 17a
43 . 66 ± 0 . 15a
43 . 62 ± 0 . 10a
42 . 79 ± 0 . 12a
43 . 21 ± 0 . 11a
10 . 50 ± 0 . 04a
10 . 40 ± 0 . 05a
10 . 50 ± 0 . 02a
10 . 40 ± 0 . 04a
10 . 30 ± 0 . 05a
10 . 50 ± 0 . 02a
10 . 30 ± 0 . 02a
10 . 50 ± 0 . 01a
10 . 40 ± 0 . 01a
6 . 80 ± 0 . 01f
7 . 38 ± 0 . 01a
6 . 93 ± 0 . 01e
7 . 04 ± 0 . 02d
7 . 08 ± 0 . 01d
7 . 14 ± 0 . 01c
7 . 12 ± 0 . 03c
7 . 22 ± 0 . 01b
7 . 35 ± 0 . 01a
0 . 158 ± 0 . 006a
0 . 164 ± 0 . 004a
0 . 160 ± 0 . 003a
0 . 161 ± 0 . 006a
0 . 160 ± 0 . 004a
0 . 160 ± 0 . 003a
0 . 162 ± 0 . 009a
0 . 162 ± 0 . 008a
0 . 160 ± 0 . 005a
35 . 88 ± 10 . 16a
27 . 00 ± 4 . 16bc
16 . 27 ± 7 . 00f
22 . 25 ± 5 . 50d
30 . 20 ± 6 . 70b
33 . 36 ± 11 . 10ab
18 . 11 ± 8 . 90e
23 . 50 ± 7 . 50cd
26 . 50 ± 10 . 10c
W: ice cream with 100% cow milk; C: ice cream with 100% coconut milk; S: ice cream with 100% soy milk; SW1:
ice cream with 75% soy + 25%cow milk; SW2: ice cream with 50% soy + 50% cow milk; SW3: ice cream with 25%
soy + 75%cow milk; SC1: ice cream with 75% soy + 25% coconut milk; SC2: ice cream with 50% soy + 50% coconut
milk; SC3: ice cream with 25% soy + 75% coconut milk .
B
means values ± standard deviation .
_
a f
Means in the same column followed by different letters were significantly different ( p < 0 . 05) .
Physical Properties of Vegetable Milk Ice Cream
991
poor solubility in water (Tangsuphoom, 2008), therefor it
s respectively; Table 3). This could be explained by soy protein
contributes to increase in the percentage of unbound water
properties which able to provide several functionalities such as
(freezable water) in ice creams. Therefore, the freezable water
water holding and emulsifying properties (Akesowan, 2009).
amount was not the factor for the reduction in melting rate of ice
Hence soy proteins form a stable network like a gel structure which
creams containing composite milk, because melting rate increased
create greater resistance to flow (Batista et al., 2005). This is
with increasing freezable water (Hwang et al., 2009).
agreement to previous studies which showed grape wine less
Another effective factor on melting rate of ice creams is their
differences in apparent viscosity. Ice creams containing coconut
(Hwang et al., 2009) and inulin (Pinto et al., 2012) water retention
effects and subsequent increase apparent viscosity of ice cream.
milk had higher melting rate because they had higher apparent
Melted ice creams containing coconut milk had a higher
viscosity than ice creams containing cow milk. On the other hand,
apparent viscosity than ice creams containing cow milk. This could
our results show the major contribution to the difference in melting
be due to the higher particle size of ice creams containing coconut
rate can be attributed to the differences in apparent viscosity of the
milk because coconut proteins have poor emulsifying properties
ice creams. This is because, ice creams containing higher amount
(Tangsuphoom and Coupland, 2009). This is in contrast to the
of soy milk has the lowest melting rate, and highest apparent
effects of the milk protein concentrates in ice cream which increase
viscosity.
the viscosities due to the increased voluminosity of the dispersed
Rheological measurements
The apparent viscosity, flow
particles as described by the Eilers equation (Alvarez et al., 2005).
behavior index and consistency index of the melted ice creams
The ice creams rheological behavior after the reduction of
made with different milk are shown in Table 3. W and C (289 and
shear rate (downward curves) is as shown in Table 3. All ice
363 mPa s respectively which are ice creams without soy milk)
creams demonstrated non-Newtonian behavior, i.e. their viscosity
melted ice creams had lower apparent viscosity than those
decreases with increasing shear rate (Fig. 2). The viscosity
containing soy milk. The highest apparent viscosity was in S ice
reduction is known to be dependent on the aggregation of fat
cream (1120 mPa s), followed by SC1 and SW1 (982 and 818 mPa
globules which decrease in size during shearing (Rossa et al.,
Table 3 . Rheological parameters of the ice creams obtained using the Power Law model
SamplesA
W
C
S
SW1
SW2
SW3
SC1
SC2
SC3
W
C
S
SW1
SW2
SW3
SC1
SC2
SC3
a
Apparent viscosity
(mPa s)b
upward curves
289 ± 0 . 80h
363 ± 1 . 16g
1120 ± 1 . 06a
818 ± 1 . 20c
488 ± 2 . 01f
398 ± 1 . 01g
982 ± 1 . 30b
739 ± 0 . 91d
603 ± 1 . 80e
Downward curves
287 ± 1 . 07h
294 ± 1 . 16h
1012 ± 0 . 91a
784 ± 1 . 11c
536 ± 0 . 87f
391 ± 0 . 96g
817 ± 1 . 09b
667 ± 1 . 03d
577 ± 2 . 06e
K (Pa sn)b
nb
R2c
0 . 87 ± 0 . 01g
1 . 29 ± 0 . 01f
4 . 67 ± 0 . 01b
3 . 10 ± 0 . 01c
1 . 30 ± 0 . 03f
1 . 18 ± 0 . 02f
4 . 81 ± 0 . 01a
2 . 89 ± 0 . 03d
2 . 17 ± 0 . 02e
0 . 65 ± 0 . 01a
0 . 56 ± 0 . 01a
0 . 51 ± 0 . 01a
0 . 55 ± 0 . 01a
0 . 68 ± 0 . 01a
0 . 63 ± 0 . 01a
0 . 47 ± 0 . 01a
0 . 55 ± 0 . 01a
0 . 59 ± 0 . 01a
0 . 994
0 . 996
0 . 996
0 . 999
0 . 998
0 . 997
0 . 999
0 . 999
0 . 993
0 . 71 ± 0 . 02f
0 . 76 ± 0 . 01f
3 . 61 ± 0 . 01a
2 . 66 ± 0 . 01b
1 . 83 ± 0 . 03c
1 . 22 ± 0 . 01e
2 . 43 ± 0 . 01b
1 . 87 ± 0 . 02c
1 . 62 ± 0 . 01d
0 . 69 ± 0 . 01a
0 . 68 ± 0 . 01a
0 . 57 ± 0 . 01a
0 . 58 ± 0 . 01a
0 . 58 ± 0 . 01a
0 . 62 ± 0 . 01a
0 . 63 ± 0 . 01a
0 . 65 ± 0 . 01a
0 . 647 ± 0 . 01a
0 . 997
0 . 998
0 . 997
0 . 996
0 . 997
0 . 998
0 . 995
0 . 996
0 . 996
K = consistency index; n = flow behavior index; W: ice cream with 100% cow milk; C: ice
cream with 100% coconut milk; S: ice cream with 100% soy milk; SW1: ice cream with 75%
soy + 25%cow milk; SW2: ice cream with 50% soy + 50% cow milk; SW3: ice cream with 25%
soy + 75% cow milk; SC1: ice cream with 75% soy + 25% coconut milk; SC2: ice cream with
50% soy + 50% coconut milk; SC3: ice cream with 25% soy + 75% coconut milk .
b
Mean values ± standard deviation . Values with different letters in the same column are
significantly different ( p < 0 . 05) (Tukey test) .
c
Coefficient of determination .
F. Aboulfazli et al.
992
Fig. 2. Effect of shear rate on the apparent viscosity of ice creams.
Table 4 . Hysteresis of integral area of
shear rate sweep ice creams
Samples
W
C
S
SW1
SW2
SW3
SC1
SC2
SC3
Table 5 . Effect of milk replacement on zeta potential and
particle diameter (Dm) of fat globules of ice cream
Hysteresis (Pa)a
Samples
23 . 93 ± 0 . 96f
36 . 19 ± 1 . 14e
45 . 69 ± 2 . 03d
45 . 20 ± 1 . 51d
28 . 69 ± 1 . 30f
2 . 70 ± 1 . 81g
100 . 41 ± 1 . 42a
60 . 00 ± 1 . 61b
55 . 33 ± 1 . 59c
a
Mean values ± standard deviation .
Values with different letters in
the same column are significantly
different ( p < 0 . 05) (Tukey test) .
2012). The K (consistency index) varied from 0.87 to 4.81 Pa s−1
(Table 4). SC1, S and SW1 ice creams had the highest consistency
indexes.
W
C
S
SW1
SW2
SW3
SC1
SC2
SC3
Particle size (nm) Zeta potential (mV)
_36 . 56cd
900f
_30 . 70b
1736b
_35 . 50cd
d
1604
_36 . 87d
h
810
_37 . 60d
gh
820
_26 . 40a
g
835
_33 . 20bc
1567e
_34 . 30dc
c
1677
_26 . 70a
a
2541
_
a h
Means in the same column followed by different letters
were significantly different ( p < 0 . 05) .
behavior (Rossa et al., 2012).
The formation of hysteresis (Table 4) is an important feature of
the shear stress versus shear rate results. The fluid viscosity
The highest K values were related to ice creams containing soy
(regarding area formed between the curves of upward and
milk and also increased with increasing soy milk content which
downward) is time dependent (Rossa et al., 2012). González-
again demonstrates that the addition of soy milk increased the
Thomás et al. (2008) and Karaca et al. (2009) noted the presence
resistance to structural breakdown due to aggregation of soy
of hysteresis in their studies on ice cream. The addition of soy milk
proteins which resulted in gel formation and subsequent increase in
increased ice cream hysteresis areas in ice creams containing
water retention (Zayas, 1997).
coconut milk larger than ones containing cow milk. It is probably
The flow behavior index (n), which reflects the degree of
due to poor emulsifying properties of coconut proteins
pseudoplasticity of a fluid, ranged from 0.47 to 0.68, but the
(Tangsuphoom and Coupland, 2009) and thus a higher particle size
differences were not significant ( p > 0.05).
of ice creams containing of coconut milk which lead to a higher
The n values of upward curve were lesser than those of the
apparent viscosity ice creams containing coconut milk. Tárrega et
downward curve, indicating a decrease in the pseudoplastic
al. (2004) suggested that a high-viscosity thixotropic fluid may
properties as the shear rate decreased. The decrease in K and
indicate a larger hysteresis area than a lower viscose, even if the
increase in n can be ascribed to the structural rupture of the protein
latter undergoes a more accentuated destruction of the structure.
network of the ice cream because of shearing, which favors this
An increase in hysteresis as an outcome of higher viscosity was
Physical Properties of Vegetable Milk Ice Cream
993
Fig. 3. Micrographs (×50 magnification) of ice cream mixes with different milk: W: ice cream with 100%
cow milk; C: ice cream with 100% coconut milk; S: ice cream with 100% soy milk; SW1: ice cream with 75%
soy+25% cow milk; SW2: ice cream with 50% soy+50% cow milk; SW3: ice cream with 25% soy+75% cow
milk; SC1: ice cream with 75% soy+25% coconut milk; SC2: ice cream with 50% soy+50% coconut milk; SC3:
ice cream with 25% soy+75% coconut milk.
also reported by Debon et al. (2010) for a dairy product with inulin
and Pinto et al. (2012) for frozen yogurt containing
_34.30 mV) and fat globule size of ice cream containing cow milk
(810 _ 900 nm) was lower than others containing coconut milk
microencapsulated Bifidobacterium Bb-12. The SW3 ice cream
(1567 _ 2541 nm) (Table 5 and Fig. 3). The bigger fat globule size
showed the lowest hysteresis area, and SC1 ice cream also showed
for coconut milk ice cream can be attributed to the less surface
the largest hysteresis area. Hence, SC1 ice cream provided a firmer
activity of the coconut proteins than whey proteins (Tangsuphoom
product because more energy is required to break the ice cream
and Coupland, 2009) and thus coconut proteins are not particularly
structure due to their protein networks (Rossa et al., 2012).
effective in preventing droplet aggregation and also creating small
Effect of milk replacement on droplets suspension
droplets during or after homogenization (Onsaard et al., 2006).
Measurements of zeta potential (the electrical charge of the
This makes ice creams containing cow milk being more stable than
droplets) along with particle size can be used to predict the stability
ice creams containing coconut milk. This is supported by smaller
of ice cream emulsions. Theoretically, a high negative zeta
hysteresis areas in the ice creams containing cow milk than ice
potential prevents aggregation of the emulsion droplets and
creams containing coconut milk which indicate higher ability for
increases stability through electrostatic repulsion (Achouri et al.,
cow milk ice cream to recover their structure and viscosity (Lopez
2012). The zeta potential of fat globules was higher (more
negative) ( p < 0.05) in ice creams containing cow milk (_26.40 to
and Sepulveda, 2012).
_37.60 mV) compared to ones containing coconut milk (_26.7 to
Data from rheological studies showed increased ice creams
viscosity with increasing amount of soy milk in ice cream made
F. Aboulfazli et al.
994
Fig. 4. Effect of the replacement of cow milk with coconut and soy milks on the ice crystal-melting of ice creams measured by differential scanning
calorimetry: A) ice creams containing coconut milk, B) ice creams containing cow milk.
Table 6 . Differential scanning calorimetry analyses for ice cream mixes
Samples
W
C
S
SW1
SW2
SW3
SC1
SC2
SC3
Peak temperature Onset temperature Freezing point
(℃)
(℃)
(℃)
_3 . 82 ± 0 . 15a
_8 . 77 ± 0 . 11c
_5 . 52 ± 0 . 09a
_3 . 17 ± 0 . 10a
_6 . 93 ± 0 . 12a
_4 . 53 ± 0 . 14a
_3 . 90 ± 0 . 13a
_8 . 50 ± 0 . 11c
_5 . 21 ± 0 . 12a
_3 . 44 ± 0 . 21a
_7 . 77 ± 0 . 19b
_5 . 00 ± 0 . 10a
_3 . 75 ± 0 . 14a
_7 . 91 ± 0 . 13b
_5 . 31 ± 0 . 17a
_3 . 68 ± 0 . 22a
_7 . 86 ± 0 . 21b
_5 . 01 ± 0 . 21a
_3 . 70 ± 0 . 11a
_7 . 86 ± 0 . 10b
_5 . 06 ± 0 . 16a
_3 . 72 ± 0 . 16a
_7 . 91 ± 0 . 18b
_5 . 48 ± 0 . 11a
_3 . 70 ± 0 . 12a
_7 . 40 ± 0 . 11b
_4 . 94 ± 0 . 19a
Freezable water
(%)
ΔHf (J/g)
32 . 50 ± 1 . 18e
39 . 61 ± 1 . 21a
31 . 91 ± 1 . 40d
31 . 68 ± 1 . 03d
34 . 62 ± 1 . 05c
38 . 61 ± 2 . 11ab
34 . 07 ± 1 . 07c
34 . 64 ± 1 . 04c
37 . 47 ± 1 . 09bc
108 . 57 ± 4 . 10d
132 . 29 ± 5 . 20a
106 . 57 ± 3 . 10d
105 . 81 ± 6 . 00d
115 . 65 ± 4 . 80c
128 . 96 ± 5 . 30ab
113 . 79 ± 5 . 60c
115 . 72 ± 6 . 20c
125 . 16 ± 6 . 10bc
ΔHf = Enthalpy of fusion
_
a e
Means in the same column followed by different letters were significantly different ( p < 0 . 05)
with composite milk. This can be attributed to the change in
water in the sample (Hwang et al., 2009). The moisture content
microstructure whereas the reduction in the fat particle diameters
was highly likely not the factor for the reduction in the enthalpy in
(Fig. 3) related in an increase in consistency index (K value; Table
3) and thus the increased product stability (Chiewchan et al.,
the present study because all ice creams had the same moisture
content (total solid ice creams ~ 43 _ 44). This makes the freezable
2006).
water amount as the most probable reason (Table 6). Increasing soy
The thermal properties of ice creams with different milks The
milk proportion and hence soy protein in ice creams made with
thermal properties associated with ice crystal-melting of ice creams
composite milks could have increased water retention (Akesowan,
with different milk (Fig. 4) were measured by differential scanning
2009) and subsequently a decrease in amount of freezable water
calorimetry (DSC). There is no significant difference in the peak
and thus the melting rate. A positive relationship between the
temperature (Tp) and in the freezing point (Tf) between the ice
enthalpy of ice-melting transition and the amount of freezable
creams. However, there is some variation in the ice cream
water have been previously reported in wheat- and soy-containing
containing purely (100%) individual milk in their onset temperature
breads (Vittadini and Vodovotz, 2003) and ice cream containing
(T0). They showed the highest of T0 in C ice cream and the lowest
grape wine lees (Hwang et al., 2009).
in S and W ice creams. The enthalpy for the ice crystal melting of
Sensory evaluation
Mean scores of flavor, body-texture and
W, S, C, SW1, SW2, SW3, SC1, SC2 and SC3 was 108.57, 118.74,
taste and color of the samples are shown in Table 7. That the
132.29, 105.81, 115.65, 128.96, 113.79, 115.72 and 125.16 J g 1,
replacement of milk by vegetable milks decreased the body-texture,
respectively. The enthalpy values associated with the ice melting
color and taste. The creaminess, structure, aroma, color and flavor
transition decreased with the addition of soy milk in ice creams
of the products decreased with increasing amount of soy milk
containing composite milks. Two possible factors affect enthalpy
( p < 0.05). The total acceptability decreased with increasing soy
value i.e. the final moisture content and the amount of freezable
milk content in ice creams because of soy milk woody or beany off
_
Physical Properties of Vegetable Milk Ice Cream
995
Table 7 . Organoleptic property scores of ice creams with different milksA
Samples
W
C
S
SW1
SW2
SW3
SC1
SC2
SC3
A
Colour and
Body and Texture Flavor and Taste
Appearance (1-5)
(1-5)
(1-10)
4 . 08 ± 0 . 05ab
3 . 25 ± 0 . 04c
3 . 12 ± 0 . 04dc
3 . 71 ± 0 . 05b
4 . 12 ± 0 . 06a
4 . 17 ± 0 . 07a
2 . 83 ± 0 . 07d
3 . 04 ± 0 . 06dc
3 . 12 ± 0 . 04dc
4 . 04 ± 0 . 04a
3 . 21 ± 0 . 05b
3 . 00 ± 0 . 05bc
3 . 70 ± 0 . 03a
4 . 08 ± 0 . 02a
3 . 91 ± 0 . 06a
2 . 62 ± 0 . 07c
2 . 85 ± 0 . 04bc
2 . 79 ± 0 . 05bc
7 . 92 ± 0 . 05ab
6 . 50 ± 0 . 06dc
5 . 08 ± 0 . 03e
6 . 42 ± 0 . 04a
7 . 17 ± 0 . 02bc
8 . 42 ± 0 . 05a
5 . 58 ± 0 . 03de
5 . 34 ± 0 . 05e
6 . 00 ± 0 . 03de
Total
(1-20)
16 . 04 ± 0 . 05a
12 . 96 ± 0 . 03c
11 . 20 ± 0 . 02d
13 . 83 ± 0 . 05bc
15 . 37 ± 0 . 06ab
16 . 50 ± 0 . 04a
11 . 03 ± 0 . 07d
11 . 23 ± 0 . 05d
11 . 91 ± 0 . 05dc
Mean values from 16 panelists .
Means in the same column followed by different letters were significantly different ( p < 0 . 05) .
_
a e
flavors (Abdullah et al., 2003).
Ice creams containing cow milk had the highest total
AOAC. (2005). Official Methods of Analysis. 16th ed. Association of
Official Analytical Chemists. Arlington,VA, USA.
acceptability than ice creams containing coconut milk. The highest
Batista, A. P., Portugal, C. A., Sousa, I., Crespo, J. G., and Raymundo, A.
total acceptability was found in W and SW3 ice creams and the
(2005). Accessing gelling ability of vegetable proteins using rheological
lowest in S, SC1 and SC2 ice creams. None of the ice-creams were
judged to be weak, crumbly, sandy or fluffy.
In conclusion, examination of selected physical properties
showed significant differences among ice creams containing
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Acknowledgement
We acknowledge the financial support of
University of Malaya Research Grant (PV113-2012A).
Dervisoglu, M., Yazici, F., and Aydemir, O. (2005). The effect of soy
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