nanorod zinc oxide

International Journal of Biological Macromolecules 99 (2017) 1–7

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International Journal of Biological Macromolecules journal homepage: www.elsevier.com/locate/ijbiomac

Preparation and characterization of bionanocomposite film based on tapioca starch/bovine gelatin/nanorod zinc oxide Mohammad Mehdi Marvizadeh a , Nazila Oladzadabbasabadi b , Abdorreza Mohammadi Nafchi c,∗ , Maryam Jokar d a

Young Researchers and Elite Club, Damghan Branch, Islamic Azad University, Damghan, Semnan, Iran Department of Chemical Engineering, Shahrood Branch, Islamic Azad University, Shahrood, Iran c Food Biopolymer Research Group, Food Science and Technology Department, Damghan Branch, Islamic Azad University, Damghan, Semnan, Iran d Research Group for Nano-Bio Science, National Food Institute, Technical University of Denmark, Mørkhøj Bygade 19, 2860 Søborg, Denmark b

a r t i c l e

i n f o

Article history: Received 21 December 2016 Received in revised form 2 February 2017 Accepted 17 February 2017 Keywords: Tapioca starch ZnO nanorod Bovine gelatin

a b s t r a c t To exploring a nano-packaging materials for using as coating or edible films, tapioca starch/gelatin/nanorod ZnO (ZnO N) bionanocomposites were prepared via solution casting technique. The effects of nanofiller addition on the mechanical, physicochemical, and crystalline structures, as well as the barrier properties of bionanocomposite films were investigated. X-ray diffraction analysis showed that the bionanocomposite film incorporated with ZnO N at a concentration of 3.5% w/w exhibited high intensity peaks compared with control samples. Results of UV–vis spectra analysis showed that incorporation of ZnO N into the films can absorb the whole UV light. Tensile strength of the films was increased from 14 to 18 MPa whereas elongation at breaks decreased from 18 to 8 percent and oxygen permeability decreased from 151.03 to 91.52 cm3 ␮m/(m2 –day) by incorporation of 3.5% ZnO N into biopolymer matrix. In summary combined starch/gelatin films supported by ZnO N showed better properties compared to starch or gelatin alone. Thus, the bionanocomposite films can be used in food, medicine, and pharmaceutical packaging. © 2017 Elsevier B.V. All rights reserved.

1. Introduction The aim of food packaging is to increase food shelf life by avoiding bacterial contamination, spoilage, or the loss of food nutrient [1,2]. Petroleum-derived polymers that are currently used in food industries are from non-renewable resources and yield non-biodegradable plastic materials [3]. With advantages such as abundance, relatively low cost, biodegradability, and edibility, natural polymers, such as starch and gelatin, have been the focus of current research. Starch is a widely available renewable resource and can be obtained from different by-products of harvesting and raw material industrialization. The unique capacities of proteins to form network and induce plasticity and elasticity are beneficial in preparing biopolymer-based packaging materials. Hence, bovine gelatin can be used as a basic raw material for the development of food packaging films [4]. Coating and biodegradable films are used not only to protect food quality but also to enhance safety

∗ Corresponding author. E-mail addresses: [email protected], [email protected] (A. Mohammadi Nafchi). http://dx.doi.org/10.1016/j.ijbiomac.2017.02.067 0141-8130/© 2017 Elsevier B.V. All rights reserved.

and stability [5]. The properties of natural packaging may lead to the development of new products, such as individual packaging of particulate foods, nutrient supplements, and carriers for different additives [6,7]. The use of nanotechnology in food packaging has led to extended shelf life, better traceability of food products, healthier food, and safer packaging. The oxidation of fats and oils and the growth of microorganisms present a major problem owing to oxygen inside food packaging. In addition, oxygen accelerates the processes inside food packaging, leading to discoloration, changes in texture, rancidity and off-odor, and flavor problems [8]. Nanotechnology can effectively produce oxygen scavengers for sliced processed meat, nuts, beverages, cooked pastas, and ready-to-eat snacks, moisture absorber sheets for fresh meat, poultry, and fish, and ethylenescavenging bags for fruit and vegetable packaging [9]. There are many efforts to finding application of biocomposites in pharmaceutical and medical application by mixing different source of biopolymers [2,10]. The main limitation of biopolymer application in food and pharmaceutical application is hydrophilic nature of the biopolymers. Recent reports on nanoparticle application were showed that application of metal oxide nanoparticles can decrease hydrophilic nature of biopolymers and can improve

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60 ± 5 ◦ C for 60 min. Nano- solutions were exposed to ultrasound in an ultrasonic bath (Marconi model, Unique USC 45 kHz, Piracicaba, Brazil) for 30 min to obtain homogeneous mixture. Nano-film were fabricated according to the solution intercalation technique with formulation 4 g of starch and 3.6 of bovine gelatin. About 1.6 g of glycerol and sorbitol (1:3) was added to dispersion as plasticizer in accordance with Abdorreza et al. [23]. Solutions bionanocomposites were heated to 87 ◦ C for 45 min. Nano- dispersions were cooled to ambient temperature (37 ◦ C). Approximately 92 mL of the solution was cast on casting plates with special dimension (16 cm × 16 cm). The bionanocomposites films were dried in special condition in 30 ◦ C and 50% RH. Tapioca starch/bovine gelatin films were fabricated similarly but without the incorporation of nanoadditives. Edible films based on starch/gelatin were removed from solution casting plates and conditioned at approximately 28 ± 2 ◦ C and 50 ± 5% relative humidity (RH) in a desiccator using saturated magnesium nitrate. Manual micrometer was used for measurment thickness of different films 2.3. Characterization of starch/gelatin nanocomposite films Fig. 1. Environmental scanning electron microscopy micrograph of nanorod-rich ZnO.

UV-shielding of the respective packaging film materials [11–14]. Bionanocomposites are combinations of natural polymer and organic or inorganic nanofillers with particular geometry, surface chemistry and size, properties [15]. Bionanocomposites exhibit significant improvements in mechanical properties, solvent or gas resistance, and dimensional stability with respect to the pristine polymer [12,16,17]. ZnO, TiO2 , MgO, and CaO among inorganic materials are of particular interest owing to the safety of such materials for animals and humans, as well as the stability under harsh condition processes [18]. Several works have reported on biopolymer improvements by the incorporation of nanoparticles, such as nano-zinc oxide [4,19–21]. To the best of our knowledge there is no report on ZnO nanoparticle in a mixed biopolymeric system, so the purpose of this work was to evaluate ZnO N effects on XRD pattern, mechanical, physicochemical, opacity, oxygen permeability, and sorption isotherm properties of tapioca starch/bovine gelatin films.

2.3.1. Hydrophobicity measurements Hydrophobicity characterization of the starch/gelatin/ZnO N films was conducted by water contact-angle measurements according the method described by Nafchi et al. [24]. Static contact angle was performed on a contact-angle meter (CAM-PLUS, Tantec, Germany). Static contact angles on each sample surface were measured after the addition of 1 ␮L deionized water immediately using the Sessile Drop Half-AngleTM Tangent line method. Experiment was carried on eight independent determinations at different sites of the film samples. 2.3.2. Moisture sorption isotherm The moisture sorption isotherm of the film samples at room temperature was studied according to Bertuzzi et al. [25] with some modifications [26]. Moisture content equilibrium of bionanocomposite films (dried basis) was estimated in triplicate in each aw that equal to equilibrium relative humidity (ERH) that provided by saturated salts. A third-order polynomial equation for the sorption isotherm was also fitted to the practical data according Hazaveh et al. [27]: W = Ba3 w + Ca2 w + Daw

2. Materials and methods 2.1. Materials Tapioca starch was purchased from SIM Company Sdn. Bhd. (Penang, Malaysia), and bovine gelatin (Type B) was purchased from Sigma Chemical Co (St. Louis, MO, USA). Liquid sorbitol and glycerol were purchased from Liang Traco (Penang, Malaysia). All chemicals include chemicals that used in moisture sorption isotherm (LiCl (aw = 0.11), KC2 H3 O2 (aw = 0.22), MgCl2 (aw = 0.33), K2 CO3 (aw = 0.44), Mg(NO3 )2 (aw = 0.52), NaBr (aw = 0.58), NaCl (aw = 0.75), KCl (aw = 0.85), KNO3 (aw = 0.93), and dried P2 O5 (aw = 0.00)) were of analytical grade. Zinc oxide nanorod (ZnO N) was synthesized through the catalyst-free combustoxidized mesh (CFCOM) process [22]. The structure of ZnO N is illustrated in environmental scanning electron microscopy micrographs of Fig. 1. It reveals that ZnO N possesses dimensions lower than 100 nm.

where aw is water activity; B, C, and D are the constant factors of polynomial equation and W is the moisture content (dry basis). 2.3.3. Light absorbance All films were cut in equipment cell dimension and placed in the location of the sample without cells. Then, the light absorbance of the bionanocomposite films was measured at wavelengths between 190 and 1100 nm by using a UV–vis spectrophotometer model UV-1650PC (Shimadzu, Tokyo, Japan) with air as the reference [28]. 2.3.4. FTIR absorption spectra The functional groups of starch/gelatin based films blending of ZnO N were observed using an FTIR-attenuated total reflectance (ATR) spectrometer (Thermo Scientific, Madison, USA) [29]. Each thin film was applied onto the ZnSe ATR cell. The spectral range for each spectrum varied from 700 cm−1 to 4000 cm−1 with 32 consecutive points and a resolution of 4 cm−1 .

2.2. Bionanocomposite film preparation ZnO N was added to water at different concentrations (0.5%, 2%, and 3.5% w/w of total solid). The dispersion was stirred at

2.3.5. Color evaluation CIELAB color values (L*, a*, b*, c∗, and h) were measured using a colorimeter (Minolta CM-3500D; Minolta Co. Ltd., Osaka, Japan),

M.M. Marvizadeh et al. / International Journal of Biological Macromolecules 99 (2017) 1–7 Table 1 Effects of ZnO N on static contact angle and oxygen permeability of tapioca starch/bovine gelatin biocomposites. ZnO nanorod (%)

Contact Angle (◦ )

Oxygen Permeability [cm3 ␮m/(m2 –day)]

0.0 0.5 2.0 3.5

62.48 ± 0.87d 66.32 ± 1.19c 71.41 ± 0.45b 78.26 ± 1.05a

151.03 ± 3.49a 129.66 ± 4.27b 105.76 ± 2.16c 91.52 ± 1.73d

Values are mean (n = 3) ± SD. Different letters in moisture content, moisture uptake and solubility column values represent significant difference at 5% level of probability among tapioca starch/bovine gelatin films.

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2.4. Statistical analysis and curve fitting ANOVA and Tukey’s post hoc tests were used to compare the means of the physical, barrier, and mechanical properties of starch/gelatin films at 5% significance level. Statistical analyses were conducted using GraphPad Prism 5 (GraphPad Software Inc., La Jolla, USA). Curve fitting for the GAB sorption isotherm was evaluated by non-linear regression using the solver module in Microsoft Excel 2010. 3. Results and discussions 3.1. Appearance of bionanocomposites films

and color parameters were computerized in a system using Spectra Magic software version 2.11 (Minolta Cyberchrom Inc., Osaka, Japan). In this paper, both reflection and transmission colorimetry of duplicate film samples were obtained. The instrument was calibrated using a zero-transmittance calibration plate CM-A100, with air indicating full transmittance prior to use. A large size aperture was used [30]. L∗ represents the difference between light (L∗ = 100) and dark (L∗ = 0). The component a∗ represents the difference between green (− a*) and red (+ a*), component b∗ represents the difference between blue (− b*) and yellow (+ b*), and h is the hue angle expressed in degrees, with 0◦ being a location on the + a* axis, continuing to 90◦ for the + b* axis, 180◦ for − a*, 270◦ for − b*, and back to 360◦ = 0◦ . C* (sauternes) was computed using the following equation. C∗ =



a2 + b2

2.3.6. Oxygen permeability Permeability to oxygen gas (OP) evaluation was conducted based on ASTM standard D3985-05 with some modification [31]. Mocon Oxtran 2/21 (Minneapolis, USA) equipment was used to esti® mate the OP with a colometric sensor (Coulox ) and WinPermTM permeability software. The bionanocomposite film was placed on an aluminum foil mask (open area equal to 5 cm2 ) and was mounted in diffusion cells. All tests were carried out at atmospheric pressure, 25 ◦ C, and 50% RH using 21% oxygen as test gas. “Convergent by hour” mode of equipment was used to reach the steady state of oxygen transmission. The OP coefficients in cc-␮m/(m2 day atm) were calculated on the basis of films thickness.

2.3.7. Mechanical properties Mechanical tests were conducted on the films following the modified method of ASTM D882-10 [11,32]. The films were cut into 100 mm × 20 mm strips and conditioned for 48 h at 23 ◦ C and 53% relative humidity. The mechanical properties of the bionanocomposite films were measured by a texture analyzer instrument (TA.XT2, Stable Micro System, Surrey, UK). Bionanocomposite films were fixed between grips with an initial separation of 50 mm, and crosshead speed was set at 30 mm/min. Mechanical properties, such as elongation-at-break (%E) and tensile strength (TS), were calculated from the deformation and force data recorded by the software. Five replicates for every film were measured.

2.3.8. X-ray diffraction (XRD) The structure bionanocomposite films were characterized using XRD (D8-Advance Bruker AXS, USA) with Cu K␣ radiation (k = 0.154 nm) in a 2 range from 10◦ to 80◦ . XRD was used to assay the crystalline structures.

Edible films formulated without and with ZnO N easily and clearly peel off from the casting plate. As nanoparticle level increased, biodegradable films become less flexible and transparent but with a smooth surface without pores or cracks. The thickness of bionanocomposites films was approximately 0.08 mm. 3.2. Effects of ZnO N on hydrophobicity of starch/gelatin composite films The determination of the water contact angle on surfaces is one method to compare the hydrophobicity of a material. A low static contact angle represents lower hydrophobicity of the surface and high contact angle indicates higher hydrophobicity [4]. The contact angles of the films are shown in Table 1. Results show that increasing the ZnO N content of starch/gelatin biocomposites leads to increase contact angle from 62◦ to 78◦ . In other words increasing in contact angle is indicating that surfaces became more hydrophobic. Recent reports have demonstrated that ZnO could interact with water and/or ion-dipole type plasticizer. This interaction occurs between zinc atoms and the −OH groups from the water and plasticizer [33]. 3.3. Oxygen permeability The results of oxygen permeability (OP) are presented in Table 1. Oxygen permeability decreased from 151.03 cm3 ␮m/(m2 –day) for the control film to 91.52 cm3 ␮m/(m2 –day) for the bionanocomposite film containing 3.5% ZnO N. The significant decrease in oxygen permeability after the addition of nanostructure may be related to effects of nanoparticles on tortuous pathway. In other word, the phenomenon is related to the presence of nanoparticles in the matrix and tortuous pathway for oxygen gas molecules to pass through [34]. Decrease in oxygen permeability of bionanocomposites films can be explained based on model of tortuosity [35]. It illustrates that nano-filler is perpendicularly oriented to the diffusive pathway, showing that penetrating molecules should traveling in a longer diffusive pathway result in decreasing water vapour permeability [32]. Akbariazam et al. [21] reported a decrease in OP when ZnO nanoparticles increased in soluble soy protein isolate. Studies recently stated that the incorporation of nano-zinc oxide to polymer resulted in oxygen permeability decrease [31,36]. 3.4. Light absorbance and FTIR spectra The transmission of the starch/gelatin nanocomposites at wavelengths between 190 and 1100 nm is presented in Fig. 2(a). After the incorporation of ZnO N at a concentration of 2.0 and 3.5% w/w, the bionanocomposite film exhibited percent zero transmission (190–400 nm) in comparison with the control. Tapioca starch/bovine gelatin and bionanocomposite films (0.5%w/w ZnO N) in the UV range represented extremely high transmittance. The using of low level (2–3.5%) of nonoaditive decreased

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Fig. 2. (a) UV–vis transmission spectra for tapioca starch/bovin gelatin, (b) visible absorbance for starch/gelatin nanocomposite films.

Table 2 Colorimetric parameters of illuminants D of starch/gelatin nanocomposites. ZnO nanorod (%)

L*

a*

b*

c*

h

0.0 0.5 2.0 3.5

95.762 ± 0.014a 85.188 ± 0.009b 79.038 ± 0.004c 75.083 ± 0.009d

0.010 ± 0.003d 1.476 ± 0.002c 2.643 ± 0.01b 3.332 ± 0.001a

1.423 ± 0.006d 13.518 ± 0.021c 17.577 ± 0.006b 19.413 ± 0.002a

1.423 ± 0.006d 13.627 ± 0.021c 17.783 ± 0.005b 19.691 ± 0.002a

84.522 ± 0.010a 83.752 ± 0.016b 81.446 ± 0.032c 80.239 ± 0.001d

visible and IR transmission, showing that visible and IR light wɑs absorbed. These findings indicated that the bionanocomposite film can provide effective protection from UV-induced lipid oxidation in food systems. Yu et al. [34] stated that the incorporation of 4% nano-ZnO to a starch film resulted in the transmission of 3.4% UV light [34]. Different results in UV light absorption of nano-ZnO is mainly attributed to morphology of nanoparticles, which is due to optimum shape for light absorption [18]. Applerot et al. [37] studied the electromagnetic properties of ZnO nanocomposite glass; according to the group, pure glass in the UV and visible range showed extremely high transmittance. Then, the addition of nanoZnO to glass decreased UV and visible transmission. This difference in transmission is due to a large surface area of absorbing ZnO nanoparticles, that is, an increased surface area of nanoparticles and their uniform distribution on the glass surface, leading to increased UV absorption efficiency.

The results of ATR-FTIR spectra of tapioca starch/gelatin/ZnO N films revealed that there is no new band showed after the addition of nano-ZnO and showing that only physical interaction occurred between the nanofiller and the biopolymer occurs (Results not shown). Same results reported on interaction of other nanoparticles with biopolymer matrix [4,26,38]. 3.5. Absorbance colorimetric properties Fig. 2(b) represents the light absorbance of the tapioca starch/bovine gelatin bionanocomposite samples. Neat films based on starch/gelatin in the visible range (400–700 nm) exhibit extremely low absorbance. Results showed that the incorporation of nano-ZnO to biodegradable films reduced red light absorbance compared with green light. In this study, this phenomenon caused an increase in

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Fig. 3. Third-order polynomial sorption isotherm control films and 3.5% nano ZnO incorporated starch/gelatin films at 25 ◦ C.

Table 3 Colorimetric parameters of illuminants F of starch/gelatin nanocomposites. ZnO nanorod (%)

L*

a*

b*

C*

h

0.0 0.5 2.0 3.5

95.841 ± 0.001a 85.908 ± 0.012b 79.993 ± 0.003c 76.012 ± 0.012d

0.070 ± 0.011d 0.839 ± 0.001c 1.586 ± 0.012b 2.033 ± 0.007a

1.631 ± 0.017d 15.632 ± 0.027c 20.321 ± 0.011b 22.443 ± 0.001a

1.632 ± 0.016d 15.660 ± 0.027c 20.377 ± 0.010b 22.537 ± 0.001a

87.191 ± 0.409a 86.899 ± 0.041b 85.522 ± 0.035c 84.817 ± 0.018d

Table 4 Colorimetric parameters of illuminants A of starch/gelatin nanocomposites. ZnO nanorod (%)

L*

a*

b*

c*

h

0.0 0.5 2.0 3.5

95.878 ± 0.003a 86.246 ± 0.010b 80.464 ± 0.005c 76.672 ± 0.009d

0.503 ± 0.003d 4.602 ± 0.001c 6.444 ± 0.011b 7.388 ± 0.007a

1.512 ± 0.008d 14.254 ± 0.023c 18.663 ± 0.005b 20.659 ± 0.001a

1.592 ± 0.007d 14.968 ± 0.021c 19.749 ± 0.001b 21.954 ± 0.001a

71.528 ± 0.188b 72.104 ± 0.031a 70.943 ± 0.035c 70.301 ± 0.018d

Values are mean (n = 3) ± SD. Different letters in each column represent significant difference at 5% level of probability among starch/gelatin films.

a* value in bionanocomposite films. Moreover, the incorporation of nanoadditive to films increased the yellow light transmittance as compared with blue light, as the low absorbance of yellow light b* value increased in samples. The addition of the nanofiller to the composite film matrix increases the absorbance of the films. These results are consistent with the UV–vis spectra.

study are consistent with those of previous studies, as the addition of nanoparticles decreased the hydrophilic behavior of the biopolymer films [1,21,26,36]. The incorporation of ZnO N to composite biodegradable films decreases the free water content, consequently reducing the accessibility of water for enzymatic and chemical reaction and increasing food shelf life.

3.6. Sorption isotherm

3.7. Film color

The theoretical polynomial moisture sorption isotherm curves fitted to practical data for bionanocomposite films at 25 ◦ C are shown in Fig. 3. The well-fitting equation was achieved by fitting a third-order polynomial model (R2 > 0.99). Fig. 3 shows that, in the special range of 0.1 < aw < 0.9, the starch/gelatin films incorporated with ZnO N showed lower equilibrium moisture content compared with the tapioca starch/bovine gelatin films. The decrease in equilibrium moisture content of bionanocomposite films based on starch/gelatin is mainly attributed to the interaction between the plasticizer, ZnO N, and natural polymer matrix, leading to increased −OH bonds among natural macromolecules, plasticizer and nanofiller and decreasing monolayer water. Accordingly Muller et al. [33] have suggested that cation −dipole interactions occur among water, nanofiller, and/or plasticizer(sorbitol and glycerol); specifically between the zinc atom and the OH groups of the water and plasticizer [23]. The effects of nanoparticles on moisture sorption isotherm for the films in this

Colorimetric parameters of illuminants D of active films are shown in Table 2. Results indicate that the addition of nano-ZnO to active films reduced the L* parameter. Lightness of the films decreased from 95.76 to 75.08. A significant increase in a* and b* values of bionanocomposites films indicate coloration and, consequently, a significant decrease in the hue angle of active films from 84.52 to 80.24. Sauternes, which shows the range of purity of active films, significantly increased from 1.42 to 19.69.This finding showed that incorporation of the nanoparticle changed the color of films from bright white to dark yellow. The color values of illuminant F of films are shown in Table 3. The colorimetric parameters indicated that ZnO N altered the opacity properties of films significantly (P < 0.05). Samples without nanofillers were lighter (higher L* value). The L* values of the films significantly decreased, but a* and b* significantly increased, indicating the tendency toward redness and yellowness. In addition, hue angle (the indicator of leaning towards axis A) was observed

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Fig. 4. XRD patterns for the tapioca starch/bovin gelatin and bionanocomposite film (3.5%w/w ZnO N).

Table 5 Mechanical properties of tapioca starch/bovine gelatin nanocomposite films. Young modulus (MPa)

Elongation at break (%)

Tensile strength (MPa)

ZnO nano rod(%)

892 ± 48c 943 ± 62c 1169 ± 44b 1424 ± 118a

18.45 ± 1.17a 12.64 ± 0.68b 8.66 ± 0.67c 8.02 ± 0.88c

14.40 ± 0.32c 14.74 ± 0.34c 16.23 ± 0.34b 18.69 ± 0.24a

0 0.5 2 3.5

Values are mean (n = 5) ± SD. Different letters in each column represent significant difference at 5% level of probability among Tapioca starch/Bovin gelatin films.

to decrease from 87.19 to 84.82. The addition of the nanoparticle increased the magnitude of sauternes, and the increase was statistically significant. The color characteristic parameters of illuminants A for the control and ZnO N-incorporated starch/gelatin films are summarized in Table 4. With regard to L*, which shows lightness of film, nanofiller addition increased the darkness of active films. Moreover, statistically significant differences were observed among the lightness of the four films. With respect to a* and b*, which demonstrates the redness/greenness and yellowness/blueness, respectively, the addition of nano-ZnO caused a change in the parameters; however, the increase in nanofillers changed indicators once the color has changed. Regarding h and c*, which show the angle of tint and the range of purity, the bionanocomposite films changed from 71.53 to 70.30 and from 1.59 to 21.95, respectively.

nanoparticles, significant decrease was observed in E. In contrast, YM was increased by the addition of ZnO N [40]. E shows an opposite trend with tensile strength in most cases, and the YM is directly related to tensile strength. Changes in tensile strength and elongation-at-break of active films owing to the addition of ZnO N can be related to moisture content, as discussed in the preceding section. On one hand, water can perform a plasticizing function in the biopolymer matrix; on the other hand, decreasing the plasticizer content decreases the flexibility of the films, consequently increasing the TS and YM and decreasing the E [24,33]. In addition, studies have reported that the mechanical properties of the composite films is related to the interfacial interaction between the matrix and fillers [41]. As shown in previous works, nanoparticles significantly reduce E and increase TS and YM [34].

3.8. Mechanical properties 3.9. X-ray diffraction (XRD) The mechanical properties, including tensile strength (TS), elongation-at-break (E), and Young’s modulus (YM), of the bionanocomposite films are given in Table 5. Results show that incorporation of nanofillers significantly affects the tensile strength of tapioca starch/bovine gelatin films (P < 0.05). No significant difference was observed between the tensile strength of control films and active films containing 0.5 ZnO N (P > 0.05). According to Wu and others [39], the addition of nanoparticles to starch films increased the tensile strength of films. These results are attributed to the interaction between the nanofiller and the biopolymer because the nanoparticles could form hydrogen and covalent bonds with the hydroxyl groups of gelatin and starch, consequently, strengthening the molecular forces between the nanoparticles and the biopolymer. In recent studies on edible film reinforced by

The XRD patterns for the starch/gelatin films and bionanocomposite film (3.5% w/w ZnO N) are shown in Fig. 4. The introduction of nano-ZnO to the composite film matrix increases the peak intensity of the different films. The XRD patterns for control film in 2 = 28◦ shows a bend in comparison with that of the bionanocomposite film. The peak of 2 = 23◦ in edible film was related to the amorphous structure in tapioca starch. Anitha and others [42] studied the XRD patterns for cellulose acetate/zinc oxide nanoparticle; according to the group, the amorphous structure in cellulose acetate showed extremely high intensity at 2 = 23◦ . ¯ ¯ The XRD peaks were identified as (10 10), (0002), (10 11),− and ¯ reflections, respectively. The peaks can be indexed to the (11 20) rod zinc oxide phase [38].

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No major crystal indices appeared after the incorporation of nanofiller to tapioca starch/bovine gelatin films. 4. Conclusion The additions of ZnO N into the starch/gelatin films were investigated. The results clearly showed that incorporation of ZnO N effectively increased the hydrophobicity behavior of the biopolymer. Furthermore, significant decreases in the elongation–at-break and oxygen permeability of the film with the nanoparticle were found compared with the control film. The electromagnetic properties of edible films show that UV light is absorbed with the addition of small amounts of ZnO N to the biopolymer matrix. In comparison with effects of ZnO N on starch or gelatin alone effects of ZnO N is more pronounce on mixed starch/gelatin matrix. These characterizations show that the incorporation of ZnO N into starch/gelatin film is an ideal option for the development of nanopackaging for extending shelf life of foods or non-food materials. References [1] D.S. Chaudhary, J. Polym. Sci. B: Polym. Phys. 46 (2008) 979–987. [2] M.-H. Fakharian, N. Tamimi, H. Abbaspour, A. Mohammadi Nafchi, A.A. Karim, Carbohydr. Polym. 132 (2015) 156–163. [3] A. Heydari, I. Alemzadeh, M. Vossoughi, Mater. Des. 50 (2013) 954–961. [4] A. Mohammadi Nafchi, M. Moradpour, M. Saeidi, A.K. Alias, LWT—Food Sci. Technol. 58 (2014) 142–149. [5] P. Sobral, J.D. Alvarado, N.E. Zaritzky, J.B. Laurindo, C. Gómez-Guillén, M.C. ˜ P. Montero, G. Denavi, S.M. Ortíz, A. Mauri, A. Pinotti, M. García, M.N. Anón, Martino, R. Carvalho, Films based on biopolymer from conventional and non-conventional sources, in: G.F. Gutiérrez-López, G.V. Barbosa-Cánovas, J. Welti-Chanes, E. Parada-Arias (Eds.), Food Engineering: Integrated Approaches, Springer, New York, 2008, pp. 193–223. [6] L. Vermeiren, F. Devlieghere, M. van Beest, N. de Kruijf, J. Debevere, Trends Food Scie. Technol. 10 (1999) 77–86. [7] L. Nouri, A. Mohammadi Nafchi, A. Karim, Ind. Crops Prod. 62 (2014) 47–52. [8] A. Mohammadi Nafchi, R.H. Tabatabaei, B. Pashania, H.Z. Rajabi, A.A. Karim, Int. J. Biol. Macromol. 62 (2013) 397–404. [9] S. Neethirajan, D.S. Jayas, Food Bioprocess. Technol. 4 (2010) 39–47. [10] N. Oladzadabbasabadi, S. Ebadi, A. Mohammadi Nafchi, A.A. Karim, S.R. Kiahosseini, Carbohydr. Polym. 160 (2017) 43–51.

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