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Effect of Oil Type and Emulsifier on Oil Absorption of Steam-and-fried
Instant Noodles
Article in Journal of Oleo Science · May 2019
DOI: 10.5650/jos.ess18217
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Journal of Oleo Science
Copyright ©2019 by Japan Oil Chemists’ Society
J-STAGE Advance Publication date : May 16, 2019
doi : 10.5650/jos.ess18217
J. Oleo Sci.
Effect of Oil Type and Emulsifier on Oil Absorption
of Steam-and-fried Instant Noodles
Jinfeng Qi1, 2, Xiaosan Wang2, Xingguo Wang2, Casimir C. Akoh3, and Qingzhe Jin2＊
1
Jiangsu University of Science and Technology, Zhenjiang 212018, Jiangsu, CHINA
State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi 214122, Jiangsu,
CHINA
3
Department of Food Science & Technology, University of Georgia, Athens, GA, USA
2
Abstract: The effects of four different frying oils and three emulsifiers on oil absorption by steam-and-fried
instant noodles were evaluated. The blended oil (high oleic sunflower oil/soybean oil/palm oil = 24:25:1 (v/v/
v)) containing approximately 50% oleic acid was chosen as the proper frying oil due to lower oil absorption
by instant noodle compared to palm, soybean, and high oleic sunflower oils. Among the four oils, the
interfacial tension between high oleic sunflower oil and instant noodle was the lowest (0.073 mN/m),
resulting in the highest oil uptake (15.47%), while the lowest interfacial tension (0.30 mN/m) between
blended oil and instant noodle resulted in the lowest oil uptake by the fried product (12.63%). Scanning
electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were used to observe surface
properties and oil distribution. The instant noodle fried in blended oil was found to have uniform oil
distribution and smooth surface. After selecting the proper frying oil, three emulsifiers (soybean lecithin,
Tween-80, Span-80, at 0.2% (v/v)) were added to the blended frying oil. Adding emulsifier into frying oil
significantly decreased the interfacial tension between frying oil and instant noodle. Among the three
emulsifiers, addition of soybean lecithin resulted in the lowest interfacial tension (0.010 mN/m) and the
highest oil uptake (18.36%). Therefore, from this study, we do not recommend adding emulsifier into frying
oil.
Key words: oil absorption, steam-and-fried instant noodle, oil distribution, surface characteristics
1 Introduction
Deep-fat frying is a traditional and highly efficient
method for cooking foods. Fried foods are preferred due to
their special texture, flavor and appearance, while excessive fat intake has been linked to diseases such as coronary
heart disease, diabetes, hypertension and cancer1）.
The medium in which deep-fat frying takes place is
usually a triacylglycerol oil. Previous studies have elaborated the mechanism of oil uptake and indicated that frying
medium and emulsifier effect oil absorption2−4）, and several
researchers focused on the effect of oil type on oil absorption5−7）. However, there were different views on why oil
type affects oil absorption of fried food. Kita et al.7）reported fat absorption by French fries increased with increasing
unsaturated fatty acids（UFAs）and decreasing saturated
fatty acid content, whereas French fries fried in rapeseed
oil with the highest UFAs exhibited the lowest oil absorption compared to the other six vegetable oils5）. Besides,
another research suggested a significant correlation
between contact angle and oil uptake when potato was
fried in sunflower oil8）. Hence, more research is needed to
confirm the factor in frying oil that affects oil absorption.
In this study, palm oil, soybean oil, high oleic sunflower oil
and blended oil were selected as frying oils. Among the
above four oils, high oleic sunflower oil contained the
highest UFA. We compared oil absorption when the four
oils were used as frying oil.
In addition, several researchers have shown that surfactants could decrease the interfacial tension and increase
the oil uptake of fried foods9, 10）, while Ziaiifar et al.3）reported that oil initial surface tension was important to consider in the capillary action leading to oil uptake and that
an increase in interfacial tension would cause an increase
in oil uptake. They were contrary views on the effect of the
interfacial tension, it was confusing whether increasing the
interfacial tension could result in oil uptake increased or
not. Thus the effect of surfactant on oil absorption by fried
foods needed to be evaluated. In this study, we chose three
＊
Correspondence to: Qingzhe Jin, State Key Laboratory of Food Science and Technology, School of Food Science and Technology,
Jiangnan University, Wuxi 214122, Jiangsu, CHINA
E-mail: jqzwx12@163.com
Accepted March 11, 2019 (received for review November 5, 2018)
Journal of Oleo Science ISSN 1345-8957 print / ISSN 1347-3352 online
http://www.jstage.jst.go.jp/browse/jos/
http://mc.manusriptcentral.com/jjocs
1
J. Qi, X. Wang, X. Wang et al.
emulsifiers which we added into frying oil to observe how
surfactant affects interfacial tension and evaluate their influences on oil absorption. Soybean lecithin, Tween-80 and
Span-80 were chosen as emulsifiers to evaluate how surfactants affect oil absorption.
Steam-and-fried instant noodles have been popular for a
long time due to its convenience. However, there have
been some health concerns regarding high residual oil
content, and it was also disadvantageous to food manufactures for the cost increases. Until now, the commercial
frying oil for instant noodles was palm oil. Therefore,
steam-and-fried instant noodles were used as food material
to investigate the effect of other oils containing higher
UFAs on oil absorption. Four vegetable oils with 60-95％
UFAs on oil absorption of instant noodles were chosen as
frying oils.
cording to previous studies with little modification16, 17）. 100
g powder（80 g wheat flour, 20 g tapioca starch）, 0.5 g
casein sodium, 1 g NaCI, 0.5 g NaHCO3 and 0.5 g KHCO3
were mixed with 40 g water in KMC510 mixer（KENWOOD,
Shanghai, China）
for 4 min on medium speed and then set
aside to rest for 30 min. The dough was first formed into a
dough sheet by passing through the rolls of a noodle
machine（Marcato Atlas-motor Wellness 150, Italy）, and
then reduced to a final thickness of around 10 mm through
a chopper. The strip was steamed at 100℃ for 6 min. After
cooling it to room temperature, the noodle was put in 5 L
stainless deep fryer（YZ-3022-BC, Guangdong, China）, and
fried at 145℃ for 45 s. In this study, four different oils and
three emulsifiers were evaluated, thus one batch of instant
noodles were prepared before frying, then frying medium
was evaluated. The prepared steam-and-fried instant
noodles were drained at room temperature before analysis.
All experiments were carried out in duplicate.
2 Materials and methods
2.1 Materials
Palm, soybean, and high oleic sunflower oils were purchased from Cargill Corp（Shanghai, China）; Tween-80,
Span-80 and soybean lecithin were bought from Sinopharm
Chemical Reagent Co., Ltd（Shanghai, China）; Wheat flour
and tapioca starch was supplied by Tingyi Holding Corp
（Shanghai, China）; Casein sodium was supplied by Shenzhen Yinuo food ingredients Co., Ltd（Shenzhen, China）;
The fluorescent dye Nile red was bought from Nanjing
Oddfoni Biological Technology Co., Ltd
（Jiangsu, China）
.
2.5 Contact angle and interfacial tension
The equilibrium contact angles between frying oil and
noodles before frying were measured on a Drop Shape
Analyzer（ KRUSS, Hamburg, Germany）. The interfacial
tension was calculated from Equation 1 according to
Pinthus and Saguy9）.
2
［1＋cosθe］
γsl＝γl
−cos（θe）
Equation 1
4
2.2 Oil physicochemical properties
Fatty acid composition of four oils was analyzed according to previous research11）. Peroxide value（POV）was determined by the AOCS official method12）. Acid value was
determined according to AOCS official method 13）. Oil
surface tension was determined at room temperature on a
Tensiometer（DCAT-21, Germany）14）; Oil viscosity at 12 r/
min was measured with viscometer（ SNB-1, Shanghai,
China）at room temperature15）.
2.3 Preparation of blended oil
Preliminary research suggested frying oil containing
50％ oleic acid had good oxidation stability（ data not
shown）. In this study, palm, soybean and high oleic sunflower oils were used as base oils to prepare the blended
oil containing approximately 50％ oleic acid. Finally, the
ratio of high oleic sunflower, soybean, and palm oils was
set as 24:25:1, and the contents of palmitic, oleic, and linoleic acids in the blended oil were 7.96, 49.98, and 30.87％,
respectively.
2.4 Preparation of steam-and-fried instant noodles
The steam-and-fried instant noodle was prepared ac-
［
］
2.6 Oil content analysis
The oil content in steam-and-fried instant noodle was
determined using Soxhlet extraction method18）. Oil extraction with petrol ether was carried out in Soxhlet extractor.
2.7 Confocal laser scanning microscopy
Oil distribution within steam-and-fried instant noodle
cross sections was assessed by confocal laser scanning mito observe the
croscopy
（CLSM, Leica TCS SP2, Germany）
extent of oil penetration and its location inside the structure19）. The steam-and-fried instant noodle was sliced into
a small piece and immersed in a 1 mg/mL Nile red acetone
solution for 10 min, and then noodle piece in the glass slide
was placed into CLSM for determination. The specific parameters were 1024×1024 of the pixel of scanning model,
200 Hz of scanning speed, 543 nm of excitation wavelength,
and 638-768 nm of emission wavelength.
2.8 Scanning electron microscopy
The surface structure of steam-and-fried instant noodles
was observed with scanning electron microscopy（SEM,
20）
. The fried instant
Quanta 200, America FEI Corp., USA）
noodle was firstly removed oil with diethyl ether, and then
attached to a specimen stub using double-sided adhesive.
The micrographs were taken using×300 magnification.
2
J. Oleo Sci.
Effect of Oil Type and Emulsifier on Oil Absorption of Steam-and-fried Instant Noodles
2.9 Statistical analysis
All results are presented as means and standard deviations. Statistical analysis was performed using the Statistical Package for the Social Sciences ver. 16.0（ SPSS,
Chicago, Illinois）. The differences between means were assessed using Duncan s multiple-range test and significance
was accepted for p＜0.05.
Table 1
3 Results and discussion
3.1 Oil physicochemical properties
The fatty acid compositions of high oleic sunflower,
palm, soybean, and blended oils are showed in Table 1.
Higher than 90％ of UFA including 81.36％ of oleic acid
existed in high oleic sunflower oil, followed by 86.43％ in
blended oil and 81.49％ soybean oil. Palm oil contained the
lowest UFA（61.44％）as it contained 33.08％ of palmic
acid.
The acid value and POV of four oils were also determined, and their values ranged from 0.10-0.13 mg KOH/g
oil and 0.023-0.031 mmol/kg oil, respectively. Previous re-
Fatty acid composition and physicochemical properties of high oleic sunflower, palm,
soybean and blended oils.
Sunflower oil
Palm oil
Soybean oil
Blended oila
C12:0
ND
0.23
ND
ND
C14:0
0.04
1.04
0.08
0.08
Fatty acid composition (%)
C15:0
ND
0.04
0.01
ND
C16:0
3.84
33.08
10.92
7.96
C16:1
0.1
0.22
0.08
0.09
C17:0
0.04
0.08
0.11
0.07
C17:1
0.05
0.03
0.05
0.05
C18:0
2.88
3.55
4.17
3.54
C18:1t
ND
0.09
0.04
0.02
C18:1 n-9
81.36
46.03
20.02
49.98
C18:1 n-7
ND
0.87
1.31
0.67
C18:2t
ND
ND
0.02
ND
C18:2
9.54
13.36
52.05
30.87
C18:3 n-6
ND
0.05
1.24
0.62
C18:3 n-3
0.45
0.58
5.92
3.19
C20:1
0.29
0.21
0.26
0.27
C21:0
ND
ND
0.04
ND
C20:2
ND
ND
0.04
ND
C20:4 n-6
0.9
ND
0.41
0.63
C20:5 n-3
0.04
ND
0.05
0.04
C24:0
0.33
ND
0.13
0.22
others
0.14
0.58
3.05
1.70
UFA
92.73
61.44
81.49
86.43
SFA
7.13
37.98
15.46
11.87
Acid value (mg KOH/g oil)
0.10
0.13
0.11
0.124
POV (mmol/kg oil)
0.031
0.028
0.023
0.029
Oil viscosity (mPa・S)
36.6
28.9
24.5
17.8
ND: not detected; UFA: unsaturated fatty acid; SFA: saturated fatty acid; POV: peroxide value.
a: high oleic sunflower oil/soybean oil/palm oil = 24:25:1 (v/v/v)
3
J. Oleo Sci.
J. Qi, X. Wang, X. Wang et al.
Table 2
Effect of oil type on oil uptake by steam-and-fried instant noodles.
Oil content (%)
Surface tension
(mN/m)
Contact angle
(°
)
Interfacial tension
(mN/m)
Blended oil
12.63±0.02c
29.10±0.03b
37.10±0.57a
0.30±0.02a
Soybean oil
14.58±0.64ab
32.70±0.03a
32.00±0.28b
0.19±0.02b
Palm oil
14.30±0.05b
32.31±0.03a
31.60±0.28b
0.18±0.01b
a
a
c
Oil type
High oleic sunflower oil
15.47±0.40
32.80±0.03
25.05±0.35
0.073±0.004c
Note: Data are presented as the mean±standard deviation; a, b, c, d, e, f, the different letters in Table 2 represent
significant difference (p < 0.05), whereas the same letters are not significantly different (p > 0.05).
search had reported oil viscosity could affect oil uptake of
fried foods, residual oil with higher oil viscosity was hard to
drain after deep frying, as oil adhesion and draining dynamics were influenced by oil viscosity3）. The higher the oil
viscosity, the slower was oil migration. Among the four oils,
the blended oil showed the lowest oil viscosity of 17.8 mPa.
S, and the high oleic sunflower oil had the highest oil viscosity of 36.6 mPa.S. The differences in oil viscosity among
the four oils possibly influenced oil uptake of steam-andfried instant noodles during deep frying.
3.2 Effect of oil type on oil absorption of steam-and-fried
instant noodles
Four oils were used as frying oil and their effects on oil
absorption by instant noodles were evaluated by measuring
oil content, oil distribution and surface structure.
3.2.1 Effect of oil type on oil content in steam-and-fried
instant noodles
The frying oil type affects oil absorption of the steamand-fried instant noodles（Table 2）. Among the four oils,
the steam-and-fried instant noodle fried in high oleic sunflower oil absorbed the highest oil content（15.47％）, followed by soybean oil（14.58％）and palm oil（14.30％）.
When blended oil was used as frying oil, the steam-andfried instant noodle absorbed the lowest oil content of
12.63％, which was significantly lower than the other three
oils.
Kita et al.7）suggested higher UFA amount in frying oil
lead to higher oil uptake and higher amount of SFA lead to
lower oil uptake. In this study, highest UFA content
（high
oleic sunflower oil）caused the highest oil uptake of instant
noodle, whereas the highest SFA content
（palm oil）
did not
result in the lowest oil uptake, which indicated that the
fatty acid composition of frying oil was not the key factor
affecting oil absorption. However, fatty acid composition
was correlated with oil viscosity 21）, possibly affecting oil
absorption to a certain degree.
The surface tensions of four oils ranged between 29.1032.80 mN/m. Among them, the surface tension of blended
oil was significantly higher than the other oils. However,
previous research showed surface tension could not play a
role in influencing oil uptake10）. The contact angle between
each frying oil and instant noodle ranged from 25°to 37.1°
.
The lower contact angle was from high amount of hydrophilic compounds in instant noodles like protein, resulting
in a very low interfacial tension. The lower interfacial
tension would further result in higher oil uptake because of
increased surface hydrophobicity9）. Among the four oils,
the interfacial tension between high oleic sunflower oil and
instant noodle showed the lowest value（0.073 mN/m）, possibly resulting in the highest oil uptake. While the lowest
interfacial tension（0.30 mN/m）between blended oil and
instant noodle caused the lowest oil content of fried
product, which was similar to previous research9）.
Therefore, the data suggested oil uptake was related to
contact angle or interfacial tension between frying oil and
instant noodles. However, more research is needed to
confirm these results and determine how oil type is related
to changes in contact angle or interfacial tension.
3.2.2 Effect of oil type on oil distribution and surface characteristics of steam-and-fried instant noodles
CLSM was used to observe some important microstructural aspects such as oil location and surface morphology.
Figure 1 showed the steam-and-fried instant noodles containing the thermoresistant fluorescent probe Nile Red
which were directly observed by CLSM. In Fig. 1, red color
represented lipids and the black background was the
instant noodle water or other materials.
There was a large part of instant noodle that showed
high brightness when fried in high oleic sunflower oil, while
the other part was observed in low brightness（Fig. 1d）,
suggesting oil was not distributed uniformly. Besides, small
amount of oil remained in the outer layer, possibly resulted
in oily noodle product. When blended oil was used as frying
oil, CLSM image suggested the lowest oil absorption of
steam-and-fried instant noodle, and the surface layer of
instant noodle was free of oil（Fig. 1a）. It also showed the
oil penetrated deeply into the interior of the instant
noodles, and oil was distributed uniformly in small pores.
When fried in soybean oil, the oil in instant noodle was distributed in lump or bigger pores, whereas the instant
noodle fried in palm oil showed lower oil absorption and
also uniform oil distribution, which was consistent with the
corresponding oil content in Table 2.
4
J. Oleo Sci.
Effect of Oil Type and Emulsifier on Oil Absorption of Steam-and-fried Instant Noodles
Fig. 1
CLSM and SEM images of steam-and-fried instant noodles fried in blended oil
（a）, soybean oil（b）, palm oil（c）and
.
high oleic sunflower oil
（d）
Table 3
Effect of emulsifier on oil uptake by steam-and-fried instant noodles
Oil content
(%)
Surface tension
(mN/m)
Contact angle
(°
)
Interfacial tension
(mN/m)
Control
12.63±0.02c
29.10±0.03b
37.10±0.57a
0.30±0.02a
Tween-80
15.26±0.33b
32.63±0.05a
23.80±0.42b
0.059±0.004b
b
a
32.75±0.04
c
22.45±0.21
0.047±0.003c
26.89±0.03c
15.90±0.14d
0.010±0.000d
Emulsifier type
Span-80
16.25±0.37
Soybean lecithin
18.36±0.62a
Note: Control: blended oil with no emulsifier added; Tween-80: blended oil with 0.2% (v/v) of Tween-80; Span80: blended oil with 0.2% (v/v) of Span-80; Soybean lecithin: blended oil with 0.2% (v/v) of soybean lecithin; data
are presented as the mean±standard deviation; a, b, c, d, e, f, the different letters in Table 3 represent significant
difference (p＜0.05), whereas the same letters are not significantly different (p＞0.05).
The effects of oil type on surface properties of steamand-fried instant noodles are also shown in SEM images
（Fig. 1）. The instant noodle fried in blended oil showed
smooth surface, whereas the instant noodle fried in three
other oils presented rough surface, especially when palm
and high oleic sunflower oils were used as frying oil. Higher
surface roughness leads to higher oil uptake22）, which was
observed in the instant noodle containing the lowest oil
content when fried in blended oil and absorbed the highest
oil amount when fried in high oleic sunflower oil
（Table 2）
.
The instant noodle fried in blended oil showed smoother
surface, consequently preventing oil penetration into the
instant noodle during frying process23）. Therefore, surface
properties of fried foods reflected oil absorption to a
certain degree.
3.3 Effect of emulsifier on oil absorption of steam-andfried instant noodles
0.2％（v/v）of different emulsifiers were added to a base
oil and evaluated by measuring oil content, oil distribution
and surface structure of steam-and-fried instant noodles.
In this study, the blended oil was chosen as the base oil and
taken as control with no emulsifier added.
3.3.1 Effect of emulsifier on oil content in steam-and-fried
instant noodles
The effect of emulsifier added to frying oil on oil uptake
of the steam-and-fried instant noodles is shown in Table 3.
The oil content increased when Tween-80, Span-80 or
soybean lecithin was added into frying oil, and the corresponding oil content were 15.26, 16.25, and 18.36％, respectively. After adding emulsifier, oil uptake was significantly increased compared to the control（12.63％）. Among
the three emulsifiers, addition of soybean lecithin into
frying oil led to the highest oil absorption compared to addition of Tween-80 or Span-80.
The surface tension after adding soybean lecithin,
Tween-80 and Span-80 into blended oil were 32.63, 32.75
and 26.89 mN/m, respectively. After adding soybean leci5
J. Oleo Sci.
J. Qi, X. Wang, X. Wang et al.
Fig. 2
CLSM and SEM images of steam-and-fried instant noodles fried in blended oil containing 0.2％
（v/v）of Tween-80（a）,
Span-80
（b）, soybean lecithin
（c）
and Control
（d）.
thin into frying oil, surface tension was significantly decreased compared to control
（29.10 mN/m）
, while the other
two emulsifier additions led to increased surface tension.
Ziaiifar et al.3）suggested superficial tension was an important factor affecting oil uptake considering the capillary
action. On the contrary, in this study, adding soybean lecithin decreased oil surface tension and increased oil content
of instant noodles. This was possibly because oil absorption
was not due to capillary mechanism when soybean lecithin
was added into blended oil and this produced high amount
of bubbles during frying.
The contact angles after adding soybean lecithin, Tween80 and Span-80 into blended oil were 15.90°
, 23.80°and
22.45°
, respectively, while contact angle of control（37.10°
）
was much higher than the others. Addition of three emulsifiers significantly decreased contact angle between blended
oil and instant noodle, especially when soybean lecithin
was added, resulting in lower interfacial tension
（0.010 mN/
m）compared to control（0.30 mN/m）. Adding emulsifier
into frying oil led to decreased interfacial tension and increased oil uptake, which was consistent with previous
reports9, 10）. The oil content of instant noodle was increased
when emulsifier was added, that is, addition of emulsifier
into frying oil could not reduce oil uptake. Instead, emulsifier addition increased oil content of instant noodles.
3.3.2 Effect of emulsifier on oil distribution and surface
characteristics of steam-and-fried instant noodles
The CLSM images of oil distribution in steam-and-fried
instant noodles are shown in Fig. 2. The red color represented oil. With the addition of Tween-80 and Span-80, the
CLSM images of instant noodles showed that higher
amount of oil was distributed in larger pore compared to
control（Fig. 2a, b）, and some oil existed at the surface.
Usually, oil penetrated into the inside of instant noodle
from the water escaped channel during frying, the larger
pores produced possibly resulted from water easily passing
through the rough surface of instant noodle when Tween80 or Span-80 added into frying oil. During deep frying,
high amount of bubbles were produced in frying oil when
soybean lecithin was added, which increased the oil
foaming property and restrained the steam into the air
from foods. This resulted in only small amount of oil entering into the inner part of fried foods and most oil existed at
the surface of foods. That was the reason why CLSM image
of instant noodle showed lower brightness at the inner part
when soybean lecithin was added into blended oil compared to Tween-80 or Span-80. High oil content may be
located at the surface of instant noodles when soybean lecithin was added into frying oil.
The SEM images of the effect of emulsifier on instant
noodles were also shown in Fig. 2. Hur et al.17）reported
that emulsifiers added into frying oil affected microstructural changes of instant noodle during in vitro human digestion. In the current study, addition of emulsifier resulted
in microstructural property changes of instant noodles.
Compared to control, addition of emulsifier increased the
surface roughness of instant noodle, while rough surface
structure lead to higher oil uptake22）. Addition of soybean
lecithin implied a different surface structure
（Fig. 2c）, possibly because their oil penetration was no longer consistent
with capillary mechanism, which would produce pores
during deep frying.
From above, both SEM and CLSM images indicated that
the surface structure and oil distribution were related to oil
content of instant noodles. The smoother the surface
structure, the more uniform the oil distribution, the lower
6
J. Oleo Sci.
Effect of Oil Type and Emulsifier on Oil Absorption of Steam-and-fried Instant Noodles
Acknowledgements
This work has been supported by Jiangsu Agency of
Science and Technology［grant number BY2016022-33］;
Postdoctoral fund of Jiangsu Province［ grant number
1601034A］.
Fig. 3
T he correlation between oil content and the
interfacial tension. A correlation curve was created
by plotting oil content on the y axis vs. the
interfacial tension on the x axis, resulting in a
.
formula of y＝−1.50lnx＋11.46
（R2＝0.941）
blended oil＋soybean lecithin; b: blended oil＋
（a:
Span-80; c: high oleic sunflower oil; d: blended oil＋
Tween-80; e: soybean oil; f: palm oil; g: blended oil）
was oil uptake of noodles. Also, it was concluded there was
a correlation between oil uptake and interfacial tension. We
created a correlation curve by plotting oil content on the y
axis vs. the interfacial tension on the x axis, resulting in a
（Fig. 3）. The
formula of y＝−1.50lnx＋11.46（R2＝0.941）
interfacial tension value and the responding oil content
were derived from the data in Tables 2 and 3. Although we
observed the mathematical relationship between interfacial
tension and oil content, lots of researches still needed to
be done for further verification.
4 Conclusions
The effect of frying oil and emulsifier on oil absorption
were studied. The steam-and-fried instant noodles when
fried in blended oil absorbed the lowest oil amount compared to palm, soybean, and high oleic sunflower oils, and
may be due to its higher contact angle or interfacial
tension. The instant noodle fried in blended oil also had
uniform oil distribution and smooth surface. Addition of
soybean lecithin, Tween-80 and Span-80 into the blended
frying oil significantly increased oil uptake possibly because
their addition decreased the interfacial tension between
instant noodle and frying oil. Therefore, from this study,
the blended oil was chosen as frying oil and emulsifier is
not recommended to be added into frying oil.
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