Advances in Environmental Biology Kapok Husk Biofilm

Advances in Environmental Biology, 8(8) 2014, Pages: 2703-2708
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Advances in Environmental Biology
Journal home page: http://www.aensiweb.com/AEB/
Effect of Glycerol and Kapok Husk Loading on Properties of Soy Protein Isolate/
Kapok Husk Biofilm
1P.
Ramyah Chelve, 2Salmah Husseinsyah, 3PL Teh, 4Marliza Mosthapa Zakaria, 5Hanafi Ismail
1,2,3,4
5
School of Material Engineering, University Malaysia Perlis, 02600,Arau, Perlis, Malaysia.
School of Materials and Mineral Resources Engineering, University Sains Malaysia, 14300, Nibong Tebal, Malaysia.
ARTICLE INFO
Article history:
Received 28 February 2014
Received in revised form 25 May 2014
Accepted 6 June 2014
Available online 20 June 2014
Keywords:
Soy protein isolate
Glycerol Kapok husk
Biofilm
ABSTRACT
Soy protein isolate(SPI) and Kapok husk(KH) biofilms were prepared by casting
method. The effect of glycerol and kapok husk loading on tensile properties and
morphology of biofilms were studied. It was found that the tensile strength of SPI/KH
biofilms decreased with inceasing of glycerol content. The addition of Kapok husk in
SPI improved the tensile strength of biofilms, at 30% of glycerol content had highest
tensile strength of biofilms. The elongation at break of biofilms decreased with
increasing KH loading. At 50%of glycerol contentshowedthehighest elongation at break
compared to 30 and 40%. The modulus of elasticity of biofilm increased as KH loading
increases. The lower content of glycerol indicates highest modulus of elasticity than 40
and 50% of glycerol content. Morphology study of biofilm showed that presence of KH
enhanced the interfacial interaction and adhesion between KH filler and SPI matrix.
This indicates that KH give reinforcement in SPI biofilms.
© 2014 AENSI Publisher All rights reserved.
To Cite This Article: P. Ramyah Chelve, Salmah Husseinsyah, PL Teh, Marliza Mosthapa Zakaria, Hanafi Ismail., Effect of Glycerol and
Kapok Husk Loading on Properties of Soy Protein Isolate/ Kapok Husk Biofilm. Adv. Environ. Biol., 8(8), 2703-2708, 2014
INTRODUCTION
Currently researchers interest in biopolymer films has been renewed due to their environmental friendly
nature and their potential use in the food and packaging industries [6]. Biopolymers from abundant of natural
resources such as protein, cellulose and starch have been considered attractive alternatives for nonbiodegradable
petrochemical based plastics.Generally, proteins are lead to polysaccharides in their ability to form films with
greater mechanical and barrier properties [2]. Moreover, proteins could be alternative resource to bioplastics in
packaging applications since they are renewable, abundant, renewable, environmental friendly and
biodegradable. However, biopolymers have some limitations in applications due to high sensitivity to moisture
and poor mechanical properties.
Proteins are always depending on their structures, origin and amino acid composition. Soy protein is
extracted from soybeans used to obtain soy oil. During this process, soy flour is obtained as a secondary product
and it can be purified to obtain soy protein isolate (SPI) and soy protein concentrate (SPC), which plays
important role in agricultural by-products. Soy proteins consist of albumins and globulins, it contains 90% of
storage proteins with globular structure, composed mainly in 7S (β conglycinin) and 11S (glycinin) globulins
[5]. Soy protein isolate (SPI) is an abundantly available biopolymer, that is often used to develop edible
materials for diverse applications. Oxygen permeability (OP) and water vapor permeability (WVP) are the
barrier properties that frequently determine the ability of an edible film to protect the food product from decay
due to exposure to environment. Mechanical properties are also useful in assessing the ability of the film and
coating to protect and maintain the food’s mechanical integrity [4,12,13].
Cellulose is the most abundant renewable bioplymer found in nature. Their amorphous region can be
dissolved away by controlling acid hydrolysis, while its water-insoluble highly crystalline region can be
converted into a stable suspension by mechanical shearing [3]. Filler reinforced composites will increase the use
of these materials and their application into various sector such as automotive and packaging products. Natural
fillers are an attractive research area because natural fillers are eco-friendly, low cost, low density and
sustainable with acceptable ease of separation, mechanical properties, biodegradibility and carbon dioxide
sequestration [10]. Natural fillers from grass, hemp and ramie have already been reported as reinforcement for
soy based matrices [7]. Improvement of the physical properties of these composites via surface treatments and
filler loading have been examined [8]. Kapok (Ceiba pentandra) is now seen throughout the tropics mainly
Corresponding Author: Salmah Husseinsyah, School of Material Engineering, University Malaysia Perlis, 02600,Arau,
Perlis, Malaysia.
Fax : 04–9798178; E-mail: [email protected].
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P. Ramyah Chelve et al, 2014
Advances in Environmental Biology, 8(8) 2014, Pages: 2703-2708
because it was extensively cultivated for the fibrous kapok found in mature fruit capsules. After removal of
kapok fiber, the residues such as leaves, pod, and seeds are left as part in the field. Kapok husk is a renewable
and biomass resource which has potential to be transformed into valuable bioproducts for industrial. Moreover,
utilization of kapok husk gives economic advantage as well as reduces the environment impact. Therefore,
kapok husk are considered as potential natural filler for biopolymer to produce biocomposites film.
Plasticizers were used to increase film flexibility due to their ability to reduce internal hydrogen bonding
between polymer chains while increasing molecular spacing [1]. Generally, most plasticizers will resemble in
structure the polymers they plasticize. Thus, protein film are best plasticized by hydroxyl compounds such as
glycerol, glycols and other hydroxyl compounds. Barrier and mechanical properties of films can be controlled
by changing the plasticizers and their concentrations [1].
The objective of this study was to evaluate the effect of glycerol and kapok husk loading on tensile and
morphology of Soy Protein Isolate/ Kapok husk biofilms.
MATERIALS AND METHODS
Materials:
Soy protein isolate (SPI) was supplied by Shandong Wonderful Industrial Group Co., Ltd., Dongying,
Shandong, China. The average particle size of SPIwas approximately 63μm.
The Kapok husk (KH) powder was obtained from villages around the Perlis. Kapok pod was cleaned,
crushed and grinded to become powder. The KH powder was dried at 80°C for 24hours. The dried KH powder
was sieved using 16μm size of siever to get fine particle size.
Glycerol was used as plasticizer for SPI/ KH biofilm which was supplied by HmbG® Reagent Chemical,
Selangor, Malaysia.
Film preparation:
Soy Protein Isolate/Kapok Husk biofilms were prepared by casting technique.Glycerol stirred in 100 ml of
distilled water about 2 minutes. Soy Protein Isolate solution was produced by dispersing 8g of soy protein
powder in that solution and stirred about 15minutes in a water bath at 90°C.After the soy protein dissolved
completely, Kapok husk was added and stirred for another 15minutes. Then, Soy Protein Isolate/Kapok Husk
solution was poured into mould and dried in the oven at 50°C for 24 hours. The formulations of SPI/KH
biofilms are listed in Table 2.1.
Table 2.1: Formulations of SPI/ KH biofilms.
Types of biofilm
1
2
3
SPI (wt%)
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
Materials
KH (wt%)
0
10
20
30
40
0
10
20
30
40
0
10
20
30
40
Glycerol (%)*
30
40
50
* based of SPI wt%
Tensiletest:
Tensile test was carried out according to ASTM D882. An Instron Universal Testing Machine model 5569
equipped with 50 kN capacity cell was used. The specimen samples with size (15 x 100 mm)and crosshead
speed of 10mm/s were used. At least five replicates were tested for each sample. Tensile strength elongation at
break and modulus of elasticity were recorded from software.
Morphology study:
Scanning Electron Microscopy (SEM), model JEOL JFC 6460LA was used to analyze the fracture surface,
filler dispersion and interfacial interaction between filler and matrix of biofilm. The samples are coated with a
thin layer of palladium for conductive purpose and voltage of 10 kV.
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Advances in Environmental Biology, 8(8) 2014, Pages: 2703-2708
RESULTS AND DISCUSSION
Stress (MPa)
Tensile test:
Figure 3.1 showed the stress-strain curve of SPI/KH biofilms at 30% of glycerol content with different KH
loading. The addition of KH reduced the ductility by increasing the strength of biofilms.
6
5
4
3
2
1
0
40% KH
20% KH
Control
0
50
100
150
Strain (%)
Fig. 3.1: Stress-strain curve of SPI/KH biofilms at different Kapok husk loading.
Figure 3.2 show the effect of glycerol content on tensile strength of SPI/KH biofilms at different KH
loading. From the graph shown, as the content of glycerol increases, tensile strength decreased due to the fact
that glycerol reduces the interactions between protein chains, thus increase the chain mobility. However, 30% of
glycerol content shows higher tensile strength compared to 40 and 50%. However, the addition of KH has
increased the tensile strength of biofilms. The increases in tensile strength of SPI/KH biofilms indicates that KH
acted as reinforcing filler, at higher amount of KH yield the strength of biofilms. The strengthening of tensile
strength of biofilm due to the formation of inter molecular hydrogen bonds between SPI matrix and KH filler.
Tensile strength (MPa)
6
5
4
3
30% glycerol
2
40% glycerol
1
50% glycerol
0
0
10
20
30
40
KH loading(wt%)
Fig. 3.2: Effect of glycerol content on tensile strength of SPI/KH biofilms at different KH loading.
The effect of glycerol content on elongation at break of SPI/KH biofilms at different KH loading is shown
in Figure 3.3. It can be seen that the elongation at break increased with increasing glycerol content. The higher
content of glycerol increased the ductility of biofilms. Whereas, the elongation at break of biofilms decreased
with the increasing KH loading. The KH filler reduced the chain mobility of biofilm and enhanced the rigidity
of biofilms. The improvement of tensile strength exhibits the lower elongation at break of biofilms. The similar
decreasingtrend of elongation at break study in characterization of phytagel modified soy protein resin and
undirectional flaxyarm reinforced green composites reported by Lodha et al., [9].
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Elongation at break(%)
Advances in Environmental Biology, 8(8) 2014, Pages: 2703-2708
160
140
120
100
80
60
40
20
0
30% glycerol
40% glycerol
50% glycerol
0
10
20
30
40
KH loading (wt%)
Fig. 3.3: Effect of glycerol content on elongation at break of SPI/KH biofilms at different KH loading.
Figure 3.4 illustrates the effect of glycerol content on modulus of elasticity of SPI/KH biofilms at different
KH loading. The results indicated the modulus of elasticity of SPI/KH biofilms decreased with glycerol content.
As KH loading increases in SPI/KH biofilms, the modulus of elasticity increased. The modulus of elasticity is
an indication of the relative stiffness of biofilms. In addition, the values of modulus of elasticity, also depends
on many factors such as the ratio of filler to matrix, the orientation of filler and the adhesion between matrix.
The increase in modulus of elasticity was expected due to the KH loading increase, the filler-filler interaction
become more pronounced than filler-matrix interaction. The increased of modulus of elasticity of blend films
with addition of cellulose derivatives/soy protein isolate also reported by Zhou et al., [15].
Modulus of elasticity (MPa)
120
100
80
60
30% glycerol
40
40% glycerol
20
50% glycerol
0
0
10
20
30
40
KH loading (wt%)
Fig. 3.4: Effect of glycerol content on modulus of elasticity of SPI/KH biofilms at different KH loading.
Morphology study:
Figures 3.5-3.7 show the SEM micrograph of the tensile fracture surface of pure SPI biofilm. It can be seen
the homogeneity and smooth surface of SPI films. Figure 3.6 represents the KH was dispersed in SPI matrix. It
shows that some KH detach from SPI matrix. While, Figure 3.7 exhibits micrograph of SPI/KH biofilms at 40
wt% of KH loading. The SEM indicates that the KH have greater dispersion and adhesion in SPI matrix. It also
shows less KH pull out and detachment from matrix. Thus, KH with 40 wt% have greater interfacial interaction
between KH filler and SPI matrix, which leads to higher tensile strength as discussed previously.
Conclusion:
Tensile properties of SPI based films have been improved by addition of KH, especially with 30% of
glycerol content. The tensile strength and modulus of elasticity decreases, while elongation at break increased
with increasing of glycerol content.The biofilms with 50% of glycerol contenthighly ductile behaviour.As the
KH loading increases, the tensile strength and modulus of elasticity increased, while elongation at break
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Advances in Environmental Biology, 8(8) 2014, Pages: 2703-2708
decreased. The increases in tensile strength and modulus of elasticity due to the better interfacial interaction and
dispersion of KH into SPI matrix was observed through SEM study.
Fig. 3.5: SEM micrograph of tensile fracture.
Fig. 3.6: SEM micrograph of tensile fracture surface of pure SPI films.of SPI/KH biofilms (at 20 wt% KH).
Fig. 3.7: SEM micrograph of tensile fracture surface of SPI/KH biofilms (at 40 wt% KH).
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