Goma Guar - Fracciones de Aceite (Leer)
Goma Guar - Fracciones de Aceite (Leer)
Goma Guar - Fracciones de Aceite (Leer)
Food Hydrocolloids
journal homepage: www.elsevier.com/locate/foodhyd
Effect of guar gum with glycerol coating on the properties and oil
absorption of fried potato chips
Lin Yu b, Jinwei Li b, **, Shaodong Ding b, Feng Hang a, Liuping Fan a, b, *
a
b
State Key Laboratory of Dairy Biotechnology, Technology Center, Bright Dairy & Food Co. Ltd., Shanghai 200436, China
State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi 214122, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 12 April 2015
Received in revised form
30 August 2015
Accepted 3 October 2015
Available online 22 October 2015
Effects of guar gum with glycerol coating on the oil absorption of fried potato chips were investigated
using dye oil methods, confocal laser scanning microscopy (CLSM) and scanning electron microscopy
(SEM). The results showed that coating with guar gum and glycerol could effectively hinder the oil
absorption of fried potato chips and have no negative effects on its breaking force. Compared with
control or samples coated with guar gum, potato chips with guar gum and glycerol produced a reduction
of oil absorption by 51.8% and 34.8%, respectively. Both for control or coated potato chips, penetrated
surface oil (PSOs) was dominant in total oil (TOs), followed by structural oil (STOs) and surface oil (SOs).
Coating treatment with guar gum and glycerol could signicantly reduce the SOs and PSOs of potato
chips (P < 0.05). PSOs was the main factor which attributed to the TOs reduction of fried potato chips
after coating. CLSM photographs revealed the oil distribution pattern for control or coated sample, and
conrmed that PSOs obviously reduced after coating with guar gum and glycerol, followed by SOs. SEM
photographs indicated that guar gum, guar gum and glycerol coatings were effective in preventing oil
penetration into the potato tissue during frying process. Coating formulations not only enhance the
barrier properties of fried potato chips, but also avoid pores and cracks in the fried products with higher
toughness.
2015 Elsevier Ltd. All rights reserved.
Keywords:
Oil absorption
Potato chips
Oil distribution
Frying
Guar gum
Glycerol
Chemical compounds studied in this article:
Water (PubChem CID: 962)
Starch (PubChem CID: 439341)
Glycerol (PubChem CID: 753)
Sudan red (PubChem CID: 5910713)
Nile Red (PubChem CID: 65182)
Petroleum (PubChem CID: 6437559)
Glucose (PubChem CID: 5793)
Oleic acid (PubChem CID: 445639)
Stearic acid (PubChem CID: 5281)
Cetylic acid (PubChem CID: 985)
1. Introduction
Frying is a cooking process to achieve desirable sensory attributes such as avor, texture and appearance. One of the most
important quality changes during the process is mass transfer,
mainly represented by water loss and oil uptake, and heat transfer
(Mellema, 2003; Vitrac, Dufour, Trystram, & Raoult-Wack, 2002).
During frying, the moisture removal inevitably results in a signicant uptake of oil which amounts to around 40% of the total food
ska, & Goubowska, 2007). High oil
product weight (Kita, Lisin
* Corresponding author. School of Food Science and Technology, Jiangnan University, Wuxi 214122, China.
** Corresponding author.
E-mail address: fanliuping@jiangnan.edu.cn (L. Fan).
http://dx.doi.org/10.1016/j.foodhyd.2015.10.003
0268-005X/ 2015 Elsevier Ltd. All rights reserved.
212
method to reduce the oil content of fried foods and have no adverse
effects.
Some edible coatings, particularly hydrophilic polymers, have
the ability to be good oxygen, carbon dioxide and lipid barriers
(Albert & Mittel, 2002), which gives them potential to decrease oil
uptake in fried products. Coatings make the surface stronger and
more brittle, with fewer small voids, which reduces water evaporation and leads to less oil uptake; also, coatings alter the waterholding capacity by trapping moisture inside and preventing the
replacement of water by oil (Mellema, 2003; Singthong &
Thongkaew, 2009). On the other hand, hydrocolloids can be used
as emulsiers in composite lms (Skurtys, 2010), the surface tension between the oil and the food could also be reduced, consequently contributed to decrease oil uptake. Thus, reducing the oil
content of fried potato chips by application of coatings is an
effective method.
Among the hydrocolloids used for coating foods for frying, the
use of guar gum has been found to be effective (Garmakhany,
Mirzaei, Nejad, & Maghsudlo, 2008; Kim, Lim, Bae, Lee, & Lee,
2011; Sothornvit, 2011). Addition of plasticizer for improving mechanical properties of biodegradable lms has been extensively
reported. This increases the percentage elongation of lms by
forming hydrogen bond with the polymer and reducing polymeric
interactions (Piermaria et al., 2011; Saurabh et al., 2013). Coating
integrity is a critical factor related to adhesion and exibility,
decreasing possible discontinuities and brittle zones (Piermaria
et al., 2011). Plasticizers, which are low molecular weight components, can improve the exibility and handling of lms, maintain
integrity and avoid pores and cracks in the fried products
(Donhowe & Fennema, 1993). Polysaccharide based lms are
commonly plasticized with polyols such as glycerol (Garcia, Ribba,
Dufresne, Aranguren, & Goyanes, 2011). The addition of glycerol as
a plasticizer might contribute improvement of lms exibility and
signicantly lower tensile strength and higher elongation at break,
which allows diminishing the oil uptake (Jouki, Khazaei,
Ghasemlou, & Hadinezhad, 2013).
Khalil (1999) reported that potato strips coated with a combination of 0.5% calcium chloride and 5% pectin had the highest
reduction of oil content, but had the highest water content as well.
Tavera-Quiroz, Urriza, Pinotti, and Bertola (2012) noted that an
edible methylcellulose coating plasticized with sorbitol on potato
chips caused an oil reduction of 30%.
Researches on the oil reduction using edible coating mainly
focused on the effects of coating on the total oil content, little to
investigated effects on the oil distribution. As a consequence, one
aim of the present study was to determine the effect of guar gum
with or without glycerol on the quality, oil fraction, oil reduction
and breaking force of potato chips. Another important aim was to
investigate oil distribution patterns of fried potato chips with or
without edible coating using dye oil method and confocal laser
scanning microscopy (CLSM). The third aim was to study the difference of potato chips microstructure with or without edible
coating by scanning electron microscopy (SEM) during frying.
2. Material and methods
Ws %
W
100%
1 W TO
(1)
where W (%) and TO (%) are the water content and total oil content
of the chips (wet basis). Each sample was tested at least in triplicate.
Starch content of the potato was determined according to the
National Standard GB/T 5514-2008 in China. For each coating, each
sample was tested at least in triplicate.
Solid content was calculated as follows:
213
TOs%
TO
100%
1 W TO
(3)
SOs%
SO
100%
1 W TO
(4)
Fig. 1. Typical force vs. distance curves representing results by Texture Expert.
PSOs %
sample holder (hollow cylinder) and punctured with a stainlesssteel ball probe (P/0.25 s) at ambient temperature. During the
test, the probe was programmed to move 5.0 mm to break the chip
at a speed of 5 mm/s. The peak force (in Newtons, N), which indicates the textural hardness, was determined from the force vs.
distance curves (Fig. 1) using Texture Expert (version 6.06) software associated with the texture analyzer. At least 10 samples were
performed in each assay. The chips were prepared on the same day
that breaking force was measured.
2.3.4. Microscopic analysis
Oil distribution and the surface morphology of the fried samples
where PSO (%) is the penetrated surface oil content of the chips
(wb).
This fraction corresponds to the oil that was picked up at the end
of the frying process and penetrated into the structure of the potato
chips after cooling (PSOs). Finally, the amount of non-dyed oil
(STOs) was the structural oil content of chips expressed against the
non-fat solid content as follows:
(6)
(5)
without dye oil were analyzed using inverted CLSM and SEM,
respectively.
Microstructure observations of fried chips were done with CLSM
(Carl Zeiss, Oberkochen, Germany) equipped with a motorized focal
plane and UVeVIS sources. The CLSM microscope was used in its
uorescence mode to observe the extent of oil penetration and its
location inside the structure, or in its reective mode to observe the
topography of fried potato chips as described by Pedreschi and
Aguilera (2002). For studying location of the oil in the chips, raw
potato slices were fried simulating the above conditions directly
inside hot oil mixed with the uorochrome Nile Red (NR, N-3013)
from Sigma Chemical Co., (Color index: 3013, St. Louis, MO) at a NR
concentration of 0.0192 mg/mL according to Pedreschi, Aguilera,
and Arbildua (1999). Fried chips were observed by uorescence
CLSM directly. Image rendering for 3D reconstruction with the serial images obtained by CLSM Carl Zeiss was performed using the
Carl Zeiss LSM software (version 3.92).
214
Fig. 2. The effects of frying time on the water and oil contents of potato chips. Data
values are means SD (n 3, N 21).
Table 1
Initial water content, solid content and starch content of potato before and after blanching*.
Material
Raw potato
Blanched potato
80.5 0.6
83.3 0.4b
19.5 0.6
16.7 0.4a
*Data values are means SD (n 3, N 6). The same letter a or b in column means no signicantly different (P > 0.05).
215
Table 2
Effects of coating treatments on water content, total oil content and breaking force of potato chips*.
Coating treatments
Control
Guar gum
Guar gum glycerol
0.98 0.15a
1.76 0.02b
1.59 0.00b
63.7 1.6c
47.1 3.0b
30.7 0.7a
63.7 1.6c
52.9 0.8b
42.2 1.4a
6.27 0.62a
6.62 0.18a
8.04 0.71a
*Data values are means SD (n 3, N 9). The same letter (a, b or c) in column means no signicantly different (P > 0.05).
Fig. 3. Effect of coating treatments on total oil content and oil fractions of the potato
chips. Data values are means SD (n 3, N 9). The same letter in column means no
signicantly different (P > 0.05).
216
did not show noticeable reduction with different coating treatments (p > 0.05), but TOs, PSOs and SOs of potato chips diminished
signicantly (p < 0.05). Pedreschi et al. (2008) found that the total
oil in potato chips was absorbed almost in the initial stage of frying
once the potato slices were placed inside the hot oil. The oil absorption was controlled by frying process, especially the initial
frying stage. Coating treatment could make the surface stronger
and effectively prevent the oil's enter.
Compared with control sample, the SOs content of coated potato
chips with or without glycerol reduced 20.4% and 43.9%, respectively, and the PSOs content by 28.8% and 55.0%, respectively. Thus,
PSOs was the main factor which attributed to the TOs reduction of
fried potato chips. As reported by Dana and Saguy (2006), Pedreschi
et al. (2008), after the potato chips was removed from the fryer, a
higher temperature difference between the surface and the interior
could generate a higher negative pressure in the pore space leading
to more oil penetration into their microstructure. Coating treatment could produce a lm barrier and hinder oil penetration,
which also produce the PSOs reduction. Consequently, coatings not
only enhance the barrier properties of fried potato chips, but also
avoid pores and cracks in the fried products with higher toughness.
PSOs constituted the highest fraction of TOs during frying of
both control and coated chips. Coating treatment not only reduced
the oil content, but also varied the oil percentage in TOs. The percentages of PSOs based on the TOs content were 89.9%, 86.9% and
84.3% for control, coated with guar gum and coated with guar gum
and glycerol, respectively. This fact suggests that oil absorption in
potato chips is mainly a surface phenomenon, which is related to
the equilibrium between the adhesion and drainage of oil (Dana &
Saguy, 2006). The STOs fraction is the second important fraction in
the TOs content during frying of the control as well as the coated
chips. The percentage of STOs based on the TOs content were 6.6%,
9.4% and 11.6% for control, coated with guar gum and coated with
guar gum and glycerol, respectively. This conrms that a little of oil
penetrates into fried products. SOs was the lowest constituent of
TOs content, and neither the guar gum coating solution nor the
presence of glycerol affected the percentage of SOs based on the
TOs content signicantly.
3.6. Oil distribution and microstructure of fried potato chips
CLSM makes optical sections in the samples at different depths
(rather than physical sectioning for classical microscopy) allowed
observation of oil distribution in the crust as close to the real situation as possible (Pedreschi & Aguilera, 2002; Pedreschi et al.,
1999).
Fig. 4A, B and C show different patterns of oil distribution in
control and coated samples, respectively. Fig. 4A1, B1, C1 show that
images were taken every 5 mm as the laser penetrated down the z
axis in a potato chip. Only the oil which is in focus at different
depths in the potato chip is recorded in the image. The 3D reconstructions of the gallery of images were obtained in Fig. 4A2, B2
and C2. Lots of integrated cell could be found in control or coated
fried potato chip, and the oil mainly covered the intercellular spaces
and can't enter the integrated cell interior. A similar trend was
reported by Bouchon and Aguilera (2001), Pedreschi et al., (1999),
who revealed that oil seemed to ow through passages that present
the lowest resistance and was concentrated in concave shells
similar to an egg-box structure around the cells, with no presence
of oil in the cell interior. The larger the red (in the web version) area
is, the more the oil content is. The red area was extensive and nearly
occupied the whole potato chips of control. The oil is entirely
accumulated over the entire region (Fig. 4A2). Compared with
control sample, the red area in potato chip coated with guar gum
diminished with some free oil region (Fig. 4B2). As shown in
Fig. 4C2, the free oil region enlarged and more uniformly distributed in the potato chip for coated with guar gum and glycerol. As
shown in Fig. 4A1, the red region near surface of sample was limited
and it enlarged with the depth increasing, which is consistent with
the result of the oil fraction in fried potato chips, PSO constituted
the highest fraction of TO during frying. Fig. 5B1 and C1 show that
the oil is not uniformly located at each depth, thus, oil appeared to
be not concentrated in the entire region. Compared with control
sample, the surface layers of potato chips coating with guar gum
are free of oil (Fig. 4B1), this result conrms that at least some of the
oil does not remain in the outer layer of a potato chip, the guar gum
coating have the ability to be good lipid barrier and decrease the SO
content and oil uptake in fried potato chips. Compared to guar gum
coated sample, glycerol addition show noticeable differences with
regard to the oil location (Fig. 4C1), suggesting that some of the oil
does not penetrate deeply into the interior of the potato chip
coating with guar gum and glycerol, reduce the SO and PSO content.
Glycerol addition improved the exibility and handling of guar gum
coating, maintained integrity and avoided pores and cracks in the
fried potato chips.
The SEM photographs of potato chips (Fig. 5), control, coated
with guar gum and coated with guar gum and glycerol, were
compared. It might explain the results of oil distribution and content. The control product did not show extensive cell separation
and ruptured cells. In contrast, maintained the integrity of most
cells. This was different with the results reported by Khalil (1999),
Singthong and Thongkaew (2009). The photographs of potato chips
coated with guar gum and coated with guar gum and glycerol look
smoother than those of control chips (Fig. 5), consequently preventing oil penetration into the potato tissue during frying process.
Coating samples showed reduction in cell volume and modied the
shape as well (Fig. 5B, C).
Combined the results of oil fraction, SEM and CLSM, we found
that oil absorption was closely related to the total solid content and
the surface structure of sample. During frying coating treatment
could reduce the oil content of potato chips, but it could also partly
prevent the water evaporation (Fig. 6). For control samples, high oil
content was related to the larger passages created by the shrinkage
or damage of cell walls during frying (Fig. 6A). Coating potato chips
with guar gum could create a layer of lm, which partly hinder the
oil enter the passages created by frying (Fig. 6B). The addition of
glycerol to guar gum reduced the intermolecular forces and increase the mobility of polymer chains, making the surface of potato
chips more smooth and formation of fewer passages, which
reduced the oil absorption further (Fig. 6C).
4. Conclusions
Coating with guar gum and glycerol for fried potato chips could
effectively hinder the oil absorption of fried potato chips and have
no negative effects on its breaking force. Compared with control or
samples coated with guar gum, potato chips with guar gum and
glycerol produced a reduction of oil absorption by 51.8% and 34.8%,
respectively. Both for control or coated potato chips, PSOs was
dominant in TOs, followed by STOs and SOs. Coating treatment with
guar gum and glycerol could signicantly reduce the SOs and PSOs
of potato chips. PSOs was the main factor which attributed to the
TOs reduction of fried potato chips. Oil absorption in potato chips is,
to a large extent, dependent on the microstructure and surface
properties of samples. Coating formulations not only enhance the
barrier properties of fried potato chips, but also avoid pores and
cracks in the fried products with higher toughness. CLSM photographs conrmed that at least some of the oil does not remain in
the outer layer of the potato chip coating with guar gum, and some
of the oil does not penetrate deeply into the interior of the potato
217
Fig. 4. Fluorescence mode CLSM images of oil distribution in control (A), guar gum coated (B) and plasticized guar gum coating with glycerol (C) fried potato chips. (1) Gallery of
CLSM images at different depths. (2) 3D reconstructions of CLSM galleries shown in (1). Each image in the gallery and the 3D image: 1024 1024 mm.
218
Fig. 5. Scan electron microscope photograph of fried potato chips (A means control, B means coating with guar gum, C means coating with guar gum and glycerol).
Fig. 6. Conceptual diagram illustrating of the effect of edible coatings on water and oil transfer of potato chips: Tissue details (green cells, red oil), A means control, B means
coating with guar gum, C means coating with guar gum and glycerol. (For interpretation of the references to colour in this gure legend, the reader is referred to the web version of
this article.)
chip coating with guar gum and glycerol. SEM photographs indicated that guar gum, guar gum and glycerol coatings were effective
in preventing oil penetration into the potato tissue during frying
process.
Acknowledgments
The authors acknowledge the nancial support of China National Natural Science Foundation (Contract No. 31371812), Jiangsu
Province Natural Science Foundation (BK20131104), Fundamental
Research Funds for the Central Universities (JUSRP51501) and the
Open Project Program of State Key Laboratory of Dairy Biotechnology, Bright Dairy & Food Co. Ltd. (SKLDB2013-05).
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