Ecofriendly and Biodegradable Soybean Protein Isolate Films

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Ecofriendly and Biodegradable Soybean Protein Isolate Films Incorporated with ZnO Nanoparticles for Food Packaging Siying Tang, Zhe Wang, Wan Li, Miao Li, Qiuhong Deng, Yi Wang, Chengyong Li, and Paul K Chu ACS Appl. Bio Mater., Just Accepted Manuscript • DOI: 10.1021/acsabm.9b00170 • Publication Date (Web): 08 Apr 2019 Downloaded from http://pubs.acs.org on April 11, 2019

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ACS Applied Bio Materials

Ecofriendly and Biodegradable Soybean Protein Isolate Films Incorporated with ZnO Nanoparticles for Food Packaging Siying Tang a, Zhe Wang b,c,*, Wan Li a, Miao Li b, Qiuhong Deng b, Yi Wang c, Chengyong Li d, Paul K. Chu a,* a

Department of Physics and Department of Materials Science and Engineering, City University

of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China b

Food Science and Processing Research Center, Shenzhen University, Shenzhen 518060

c

Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic

University, Kowloon, Hong Kong, China d

Shenzhen Institute of Guangdong Ocean University, Shenzhen 518108, China

*Corresponding Authors: Paul K. Chu ([email protected]); Zhe Wang ([email protected])

KEYWORDS: Soybean protein isolate; ZnONPs; food packaging; mechanical properties; thermal stability

ACS Paragon Plus Environment

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ABSTRACT

ZnO nanoparticles (ZnONPs) are synthesized and incorporated into soybean protein isolate (SPI) to obtain SPI/ZnONPs (SZ) films and the morphology, size distribution, and stability are determined. The effects of different contents of ZnONPs in the SZ films on the oxygen barrier, antibacterial activity, as well as thermal and mechanical properties are evaluated. A ZnONPs content of 0.2% in the SZ films improves the tensile strength and microbial inhibition by 231% and 16%, respectively. The thermal stability and oxygen barrier properties of the SZ films are also enhanced with addition of ZnONPs. The ZnONPs dispersed uniformly in the SPI film enhance the interactions between SPI molecules via hydrogen bonding and the results suggest potential application of ZnONPs in food packaging.

1. Introduction Recently, research of food packaging materials has focused more on renewable and biodegradable films composed of proteins, polysaccharides, lipids, or their combinations. These films are required to have not only good biodegradability/or edibility, but also physical protection under practical conditions as well as a satisfactory shelf life.1-2 Among the various types of natural materials, soybean protein isolate (SPI) has attracted much interest due to the low cost, film formability, emulsification properties, biocompatibility, and biodegradability. Nevertheless, it tends to have poor mechanical properties, water resistance, and heat toleration thereby stifling wider application in food packaging.3-4 Attempts have been made to improve the toughness of SPI film by cross-linking using heat, chemicals, enzymes, irradiation, and nanoparticles.5-6

In


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particular, addition of inorganic nanoparticles with a large specific surface area offers advantages such as the low cost, straightforward procedures, good antimicrobial activity, and chemical inertness. The incorporated nanofillers can enhance crystallization of the SPI matrix in addition to the thermal resistance, mechanical characteristics, and barrier properties of the films.7-9 Zinc oxide nanoparticles (ZnONPs) have low toxicity and are chemically inert as well as relatively inexpensive as coating agents. They also possess attractive catalytic properties, antimicrobial properties, and the capability to enhance the thermal, barrier, and mechanical properties of polymers.10-14 Hence, it has been used in cereal-based food fortification and listed as GRAS (Generally Recognized As Safe) materials (21CFR182.8991) by the United States Food and Drug Administration (USFDA) in 2014.14-15 However, having a large specific surface area and volume effects, bare ZnONPs can easy aggregate in the solution and lose the effectiveness. Therefore, immobilization of ZnONPs in films is crucial to maintaining the desirable properties. In this work, ZnONPs are synthesized and added to SPI to produce SZ films suitable for food packaging. The size distribution, morphology, and stability of the ZnONPs are determined and the mechanical, barrier, antimicrobial, and thermal properties of the SZ films are evaluated systematically.

2. Experimental Section Materials. The soybean protein isolate (SPI, protein ≥ 90%) was acquired from Beijing Solarbio Science &Technology Co., Ltd. and zinc acetate di-hydrate (AR), diethylene glycol, sodium hydroxide (AR), and Tween 80 were purchased from Shanghai Aladdin Bio-Chem Technology Co., Ltd.

E. coli and S. enteric were provided by Guangdong Institute of Microbiology


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(Guangzhou, China). All the chemicals were analytical grade and distilled water was used throughout sample preparation. Synthesis of ZnO nanoparticles (ZnONPs). The ZnONPs were produced by hydrolysis of zinc salts in polyol under alkaline conditions.16 In brief, 0.3 g of zinc acetate di-hydrate were mixed with 15 mL of diethylene glycol and 400 μL of NaOH (0.01M) under stirring. The mixture was transferred to an autoclave and heated to 180°C for 2 hrs. The milky white precipitate (ZnONPs) was collected, cleaned with methanol three times, and dried at 60 °C. SPI/ZnONPs (SZ) films preparation. The films were fabricated using a reported method with some modifications.1 The ZnONPs solutions with different concentrations of 0.01%, 0.05%, 0.1%, and 0.2% (w/v) were sonicated for 25 min and heated to 80 °C. The SPI (4%, w/v) powder was dispersed in the heated ZnONPs solution and stirred for 40 min followed by addition of glycerol (1.0 g) and Tween 80 (0.5 g). The solutions were labeled SZ1, SZ2, SZ3, and SZ4 and the solution without ZnONPs was the control. The solution (100 mL) was degassed in vacuum for 20 min before the casting process was conducted on square plastic dishes (20×20 cm2). To produce films with a uniform thickness, the dishes were put on a level surface and dried in a chamber at 60 °C for 6 hrs. Finally, the films were preconditioned in a constant temperature and humidity chamber (25 °C, 50% relative humidity) for at least 48 hrs to normalize the moisture content before further experiments. Characterization of ZnONPs. Transmission electron microscopy (TEM) was performed to examine the ZnONPs on the FEI Tecnai G2 F20 S-Twin instrument (FEI Company, Eindhoven, Netherlands) at 200 kV. The zeta potentials were determined on the Zetasizer Nano-ZS90 (Malvern Instruments, UK) to evaluate the particle stability in the suspension against


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agglomeration.

A folded capillary cell (DTS 1070, Malvern Instruments, UK) containing 0.5

mLof the ZnONPs suspension (0.5mL) was measured at room temperature and analyzed in triplicate. Characterization of SPI/ZnONPs (SZ) films. The surface and interior morphologies of the films were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The samples were cryo-fractured in liquid nitrogen to expose the crosssection of the film. The samples were mounted on a metal stub and coated with platinum for 15 s (Bio-Rad type SC 502, JEOL Ltd., Japan) prior to conducting SEM at 5 kV (FEI Nova NanoSEM450, FEI company, Eindhoven, Netherlands). The infrared (IR) spectra were recorded on an Attenuated Total Reflectance Fourier-transform infrared (ATR-FTIR) spectrometer (Nicolet Avatar 360, Thermo Nicolet Corporation, USA) from 400 to 4,000 cm-1 employing an attenuated total reflectance (ATR) accessory with a diamond ATR crystal. X-ray diffraction (XRD) was performed on the Bruker Advance D8 (Bruker, Germany) using Cu Kα radiation (λ = 1.5438 Å) with a step size of 2θ = 0.02°. The film thickness was determined on a micrometer (Mitutoyo Manufacturing, Tokyo, Japan) with a precision of 0.001 mm. Five random locations were measured on each sample and the average thickness was used to calculate the tensile strength. The testometric machine (PARAM XLW-B Auto Tensile Tester, Labthink, Jinan, China) was employed to measure the tensile strength (TS, MPa) and elongation at break (E, %) of the films. The test was conducted at 25 ± 1 °C following the ASTM standard method of D882-01. Briefly, 120 mm × 15 mm strips cut from the films were equilibrated in a humidity chamber at a constant temperature (25 °C, 50% relative humidity) before the analysis. The strips were fastened with an initial grip separation of 50 mm before stretching.


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In the process, the cross speed was 50 mm/min and data about the strength and elongation were collected by a microcomputer. At least five measurements were performed on each sample. To determine the oxygen permeability (OP), the films were cut into round specimens with a diameter of 97 mm before conditioning in the cell of a gas permeability tester G2/132 (Labthink, Jinan, China) for 0.5 hrs. The OP values of films were determined at 23 °C and 50% relative humidity. The antibacterial activity of the films was examined using E. coli and S. enterica by an inhibition zone method. Sequential 10-fold dilution with normal saline was first conducted to form the bacterial suspensions with concentrations between 105 and 106 CFU/mL. In the qualitative experiments for the antimicrobial activity, square films (1.0×1.0 cm) were obtained from punching and put onto a modified agar diffusion assay. 200 μL of 106 CFU/mL of the E. coli and S. enterica suspension were dispensed, respectively, onto two plastic plates containing count agar (PCA, Beijing Land Bridge Technology Co., Ltd.) and the films were placed directly on the agar plates. The clear zones on the plates after incubation (37 °C, 1 day) were recorded and the antimicrobial test was performed in triplicate. The thermal stability was assessed on a thermogravimetric analyzer (TGA/DSC1, Mettler Toledo, Switzerland) by thermal gravity analysis (TGA) and differential scanning calorimetry (DSC). Approximately 5-10 mg of each sample were put on a standard aluminum pan and heated to 600 °C under flowing nitrogen (50 cm3/min) at a rate of 10 °C/min. The central finite difference method was utilized to calculate the derivative of TGA and the char content of the samples at 600 °C was determined from the TGA curve. The DSC measurement was carried out at a heating rate of 10 °C/min in nitrogen between 20 and 300 °C. Statistical analysis. The data were calculated as the mean of triplicate measurements. SPSS 10.0


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for Windows (SPSS Inc., Chicago, IL, USA) was used to conduct the analysis of variance (ANOVA) and Duncan’s multiple range tests were adopted to determine the significant difference among the means. Statistical significance was defined as p < 0.05.

3. Results and discussion Morphology and size distribution of ZnONPs. The representative TEM micrograph in Figure 1a shows that the ZnONPs are porous spheres and distributed uniformly after the ultrasonic treatment. Figure 1c shows that the mean diameter of the ZnONPs particles determined by TEM is 91±11 nm. The average zeta potential of the ZnONPs is -31±1.5 mV indicating strong electrostatic repulsion among particles (Figure 1b). The stability of the nanoparticle dispersions depends on the interactions between the particles and solvent and the negative charges on the ZnONPs surface arise from zinc salt hydrolysis under alkaline conditions.17 The larger the zeta potential (absolute value), the stronger is the repulsion and more stable the system.18-19 Hence, the absolute zeta potential (above 30 mV) indicates high stability in the aqueous medium.


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Figure 1. Morphology and size distribution: (a) TEM image of ZnONPs; (b) Zeta potentials of ZnONPs; (c) Size distribution of ZnONPs; (d) Fabrication process of the SZ film (scale bars = 10 cm).

Surface and internal morphology of the film. Figure 2a shows that the SPI film has a compact, smooth, and continuous surface demonstrating the good film-forming ability. However, SZ3 has a relatively rough surface morphology and Figure 2b shows white aggregates on the surface. Nevertheless, the two sides of the SZ3 film (Figure 2b and 2c) show completely different morphologies. Figure 2b shows a relatively smooth surface with some substances in the SPI matrix. Furthermore, the upper layer in SZ3 consists of SPI and ZnONPs rather than pure SPI according to Figure 3. Figures 2c and d reveal surface globules due to phase segregation in the SZ films. Many ZnONPs are dispersed and aggregate on the globular surface (Figure 2e) and connections


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are observed between two globules (Figure 2f). This observation demonstrates uniform dispersion of ZnONPs in the SPI matrix and the agglomerates become more regular. Therefore, they are more prone to molecular interactions such as hydrogen bonding and electrostatic forces in the SPI matrix, resulting in improved mechanical and oxygen barrier properties.

Figure 2. SEM micrographs: (a) Surface morphology of the SPI film; (b) Upper layer in the SZ3 film; (c) Bottom layer in the SZ3 film; (d) Cross-section of the SZ3 film: (e) Globular structure (50k magnification); (f) Globular structure (30k magnification).


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Figure 3. EDS spectra of the upper layer in the SZ3 film.

Molecular interactions. Figure 4a shows the results of ATR-FTIR to investigate the interactions between ZnONPs and SPI matrix. All of the films show the major peak of amide-I at 1628 cm−1 as a result of coupled C=O stretching/hydrogen bonding with the COO group. The characteristic band of the plasticizer -OH group interplayed by SPI is around 1042 cm−1, which indicates the interaction between glycerol and SPI. With regard to amide-A in the films, a broad peak near 3,278 cm−1 representing N-H stretching coupled with hydrogen bonding is observed. As for amideB, the peak near 2,980 cm−1 arises from asymmetric stretching of CH and NH3+. The intensity of amide-A (the hydrogen bonded N-H stretching vibration) around 3,278 cm−1 increases after addition of ZnONPs. The intensity increase in the amide-A region demonstrates that hydrogen bonding is responsible for the interactions between the N-H groups of the SPI chain and ZnO NPs.


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Figure 4. (a) ATR-FTIR and (b) XRD spectra of the SPI-based films.

Crystalline Structure. XRD is carried out to determine the crystal structure as well as affinity between SPI and ZnONPs. The structure of the SZ films is presented in Figure 4b and the patterns of the SZ films are similar. The wide diffraction peak at 2θ = 20° belongs to the second aryconformation β-sheet of SPI20and those at 2θ = 32°, 36°, and 56°correspond to the wurtzite


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structure of ZnONPs (JCPDS file no. 36-1451) showing good compatibility between ZnONPs and SPI.14 Mechanical properties. As shown in Table 1, the thickness of SZ film is quite different (p < 0.05) from that of the SPI film and the thickness is altered by the composition of the ZnONPs. The tensile strength (TS) and elongation at break (E) of the SPI films are 1.42±0.07 MPa and 136.05±19.79 %, respectively, and in good agreement with previously reported values for SPI films.8, 21 The TS of the SZ3 film is twice that of SPI films and increases with increasing ZnONPs until 4.7 MPa, which is twice that of the original films. The strong interfacial interaction between the ZnONPs and SPI matrix may stem from this phenomenon. However, E decreases from 136.05% to 102% due to the increase in the crystallinity after addition of 0.2% ZnONPs to the SPI films. Typically, ZnONPs act as effective fillers in the matrix and establish strong interfacial interactions with the matrix because of the large surface area. It has been reported that the interfacial interaction between ZnONPs and starch, gelatin and chitosan can be enhanced.15, 22

Table 1. Mechanical properties and oxygen permeability of the SPI/ZnONPs films. Film

Thickness

TS (Mpa)

E (%)

OP (10-8cm3cm/cm2sPa)

(µm) SPI

62.2 ± 1.79b

1.42±0.07d

136.05± 19.79c

3.08± 1.47a

SZ1

79.91 ± 13.02a

2.34±0.12c

123.6± 7.75c

1.78± 1.09a

SZ2

63.36 ± 8.27a

2.99±0.25b

162.54± 2.29b

2.54± 0.43a

SZ3

63.14 ± 5.26a

2.74±0.17b

199.63± 7.95a

2.90± 0.34a

SZ4

58.48 ± 4.68a

4.7±0.52a

102± 9.89c,d

1.90± 0.78a


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a,b,c,d

In each measurement, the data marked by different letters in a column indicate a significant difference (p < 0.05) and the values are shown as mean ± SD.

Oxygen permeability. With regard to edible polymer films in food packaging, the gas permeability is an important property23-24 and influenced by various factors such as the path tortuosity in the polymer structure, polymer chain immobilization, crystallinity degree, dispersion, variety, content, add-in ratio and direction of the filler, as well as solvent retention and porosity.2527

The oxygen permeability (OP) values of the SZ films with various contents of ZnONPs are

presented in Table 1. The SPI film shows an OP of 3.08 ± 1.47 ×108cm3cm/cm2 s Pa and the SZ film has OP in the range between 1.78 ± 1.09 and 2.90 ± 0.34 ×10-8cm3cm/cm2 s Pa. The results indicate that addition of ZnONPs to the SPI film slightly promotes the oxygen barrier property probably due to the increasing tortuosity that obstructs diffusion of oxygen through the film. The water resistance is also a vital indicator in food packaging and the permeability tends to decrease with increasing ZnONPs amounts, but the difference is not significant (Table S1). Antimicrobial properties. E.coli and S. enteric, two representative food pollution microorganisms, are chosen to assess the antimicrobial activity of the SZ films in food packaging. The results are indicated by the size of the inhibition zone as shown in Figure 5. SPI, SZ1, and SZ2 do not show any antibacterial activity but on the contrary, the SZ3 and SZ4 films exhibit distinctive antimicrobial activity against both E.coli and S. enterica. Addition of ZnONPs enhances the antimicrobial activity of the SZ films perhaps due to the irregular and sharp morphology of the ZnONPs as well as oxygen vacancies on the polar facets of the ZnNPs. The sharp edges on ZnONPs help penetration into the bacteria cell walls while oxygen vacancies enable production of reactive oxygen species (ROS) to kill bacteria.28


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Besides the concentration dependence, the activity of the samples for the two microorganisms is quite different. The antimicrobial activity of the SZ films against E. coli (gram-negative bacteria) is superior to that against S. aureus (gram-positive bacteria) as indicated by that both SZ3 and SZ4 show larger microbial inhibition zones against E.coli than S. enterica.14, 29 This difference may be attributed to the cell wall structure. Gram-positive bacteria have a cell wall constructed with a thick but single peptidoglycan layer, which permits easier entry of ZnONPs into the cell.30-31

Figure 5. Antibacterial activity of the samples against (a) E. coli and (b) S. enterica.


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Thermal stability. Figures 6a and 6b present the TGA and DSC data. As shown in Figure 6a, the first stage from room temperature to 150 °C demonstrates loss of water and desorption of small molecules from the films. The second stage from 150 to 310°C is the result of glycerol evaporation and thermal decomposition of proteins is observed from the third stage from 310 to 500°C.32 In the DSC curves (Figure 6b), the recrystallization peak at around 110 °C is observed and at around 170 °C, melting occurs. The films with ZnONPs show better thermal stability than the SPI film because of the higher thermal stability of ZnONPs, as evidenced by less decomposition of the SZ films (Figure 6a). Stronger interfacial adhesion between the ZnONPs and SPI matrix leads to restricted motion of the SPI chains giving rise to higher thermal stability of the SZ films.

Figure 6. (a) TGA and (b) DSC curves of the SPI-based films and inset in 6(b) shows the temperature (Tp).

4. Conclusion


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SPI-based films containing different concentrations of ZnONPs are prepared and evaluated. Addition of ZnONPs improves the properties of the SPI films, especially the tensile strength (TS) and antimicrobial activity. TS increases by 231%, whereas E decreases by 25.03% compared to the pure SPI films. The SZ films have better oxygen barrier properties showing an increase of 42.3% compared to the control. Furthermore, addition of ZnONPs enhances the antimicrobial ability and the higher thermal stability of ZnONPs improves the thermal stability of the SZ films. Our results show that SZ films have high potential in food packaging.

ASSOCIATED CONTENT

Supporting Information

The Supporting Information is available free of charge on the ACS Publications website.

Details of Water Vapor Permeability (WVP) values for the films

AUTHOR INFORMATION Corresponding Authors * (P. K. C.) E-mail: [email protected], Tel: [852]-34427724 * (Z. W.) E-mail: [email protected], Tel: [86]-13048853377 Author Contributions The manuscript was written through contributions of all authors.


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Funding Sources The work was jointly supported by Shenzhen overseas special fund for high-level talents [No. KQJSCX2017033116171850] and Hong Kong Research Grants Council (RGC) General Research Funds (GRF) No. CityU 11205617. Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT We would like to thank Shenzhen overseas special fund for high-level talents [No. KQJSCX2017033116171850] and Hong Kong Research Grants Council (RGC) General Research Funds (GRF) No. CityU 11205617 for the financial support.

REFERENCES (1) Wang, Z.; Zhang, N.; Wang, H.-Y.; Sui, S.-Y.; Sun, X.-X.; Ma, Z.-S. The Effects of Ultrasonic/microwave Assisted Treatment on the Properties of Soy Protein Isolate/titanium Dioxide Films. LWT-Food Sci. Technol. 2014, 57, 548-555. (2) Jensen, A.; Lim, L.-T.; Barbut, S.; Marcone, M. Development and Characterization of Soy Protein Films Incorporated with Cellulose Fibers Using a Hot Surface Casting Technique. LWTFood Sci. Technol.2015, 60, 162-170. (3) Chen, L.; Remondetto, G.; Rouabhia, M.; Subirade, M. Kinetics of the Breakdown of Crosslinked Soy Protein Films for Drug Delivery. Biomaterials2008, 29, 3750-3756. (4) Song, F.; Tang, D.-L.; Wang, X.-L.; Wang, Y.-Z. Biodegradable Soy Protein Isolate-based Materials: a Review. Biomacromolecules2011, 12, 3369-3380.


17


Page 18 of 21

(5) Zhang, H.; Mittal, G. Biodegradable Protein-based Films from Plant Resources: aReview. Environ. Prog. Sustain.2010, 29, 203-220. (6) Su, J.-F.; Huang, Z.; Yuan, X.-Y.; Wang, X.-Y.; Li, M. Structure and Properties of Carboxymethyl Cellulose/soy Protein Isolate Blend Edible Films Crosslinked by Maillard Reactions. Carbohyd. Polym.2010, 79, 145-153. (7) Dave, R. K.; Rao, T. R.; Nandane, A. Improvement of Post-harvest Quality of Pear Fruit with Optimized Composite Edible Coating Formulations. J. Food Sci. Tech.2017, 54, 3917-3927. (8) Saba, M. K.; Amini, R. Nano-ZnO/carboxymethyl Cellulose-based Active Coating Impact on Ready-to-use Pomegranate during Cold Storage. FoodChem.2017, 232, 721-726. (9) González, A.; Strumia, M. C.; Igarzabal, C. I. A. Cross-linked Soy Protein as Material for Biodegradable Films: Synthesis, Characterization and Biodegradation. J Food Eng.2011, 106, 331-338. (10) Weiss, J.; Takhistov, P.; McClements, D. J. Functional Materials in Food Nanotechnology. J. Food Sci.2006, 71, R107-R116. (11) Souza, A.; Benze, R.; Ferrão, E.; Ditchfield, C.; Coelho, A.; Tadini, C. Cassava Starch Biodegradable Films: Influence of Glycerol and Clay Nanoparticles Content on Tensile and Barrier Properties and Glass Transition Temperature. LWT-Food Sci. Technol.2012, 46, 110-117. (12) Kadam, D. M.; Thunga, M.; Wang, S.; Kessler, M. R.; Grewell, D.; Lamsal, B.; Yu, C. Preparation and Characterization of Whey Protein Isolate Films Reinforced with Porous Silica Coated TitaniaNanoparticles. J. Food Eng.2013, 117, 133-140. (13) Mirmoghtadaie, L.; Aliabadi, S. S.; Hosseini, S. M. Recent Approaches in Physical Modification of Protein Functionality. Food Chem.2016, 199, 619-627. (14) Tang, S.; Wang, Z.; Li, P.; Li, W.; Li, C.; Wang, Y.; Chu, P. Degradable and Photocatalytic Antibacterial Au-TiO2/Sodium Alginate Nanocomposite Films for Active Food Packaging. Nanomaterials2018, 8, 930-941.


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Page 19 of 21 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(15) Shankar, S.; Teng, X.; Li, G.; Rhim, J.-W. Preparation, Characterization, and Antimicrobial Activity of Gelatin/ZnO Nanocomposite Films. Food Hydrocolloid.2015, 45, 264-271. (16) Kanmani, P.; Rhim, J.-W. Properties and Characterization of Bionanocomposite Films Prepared with Various Biopolymers and ZnO Nanoparticles. Carbohyd. Polym.2014, 106, 190199. (17) Ghosh, S.; Goudar, V.; Padmalekha, K.; Bhat, S.; Indi, S.; Vasan, H. ZnO/Ag Nanohybrid: Synthesis, Characterization, Synergistic AntibacterialActivity and Its Mechanism. RSC Adv.2012, 2, 930-940. (18) Arfat, Y. A.; Benjakul, S.; Prodpran, T.; Sumpavapol, P.; Songtipya, P. Properties and Antimicrobial Activity of Fish Protein Isolate/fish Skin Gelatin Film Containing Basil Leaf Essential Oil and Zinc Oxide Nanoparticles. Food Hydrocolloid.2014, 41, 265-273. (19) Jafarzadeh, S.; Alias, A.; Ariffin, F.; Mahmud, S. Characterization of Semolina Protein Film with Incorporated Zinc Oxide Nanorod Intended for Food Packaging. Pol. J. Food Nutr. Sci.2017, 67, 183-190. (20) Beak, S.; Kim, H.; Song, K. B. Characterization of an Olive Flounder Bone Gelatin‐Zinc Oxide Nanocomposite Film and Evaluation of Its Potential Application in Spinach Packaging. J. Food Sci.2017, 82, 2643-2649. (21) Tang, C.-H.; Ma, C.-Y. Effect of High Pressure Treatment on Aggregation and Structural Properties of Soy Protein Isolate. LWT-Food Sci. Technol.2009, 42, 606-611. (22) Rhim, J.-W.; Lee, J. H.; Ng, P. K. W. Mechanical and Barrier Properties of Biodegradable Soy Protein Isolate-based Films Coated with Polylactic Acid. LWT-Food Sci. Technol. 2007, 40, 232-238. (23) Oymaci, P.; Altinkaya, S. A. Improvement of Barrier and Mechanical properties of Whey Protein Isolate Based Food Packaging Films by Incorporation of Zein Nanoparticles as a Novel Bionanocomposite. Food Hydrocolloid.2016, 54, 1-9. (24) Miller, K. S.; Krochta, J. M. Oxygen and Aroma Barrier Properties of Edible Films: aReview. Trends Food Sci. Tech.1997, 8, 228-237.


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(25) Hartman, J.; Albertsson, A. C.; Lindblad, M. S.; Sjoberg, J. Oxygen Barrier Materials From Renewable Sources: Material Properties of Softwood Hemicellulose-based Films. J. Appl. Polym. Sci.2006, 100, 2985-2991. (26) Ayranci, E.; Tunc, S. A Method for the Measurement of the Oxygen Permeability and the Development of Edible Films to Reduce the Rate of Oxidative Reactions in Fresh Foods. Food Chem.2003, 80, 423-431. (27) Ou, S. Y.; Wang, Y.; Tang, S. Z.; Huang, C. H.; Jackson, M. G. Role of Ferulic Acid in Preparing Edible Films from Soy Protein Isolate. J. Food Eng.2005, 70, 205-210. (28) Perez-Gago, M. B.; Krochta, J. M. Denaturation Time and Temperature Effects on Solubility, Tensile Properties, and Oxygen Permeability of Whey Protein Edible Films. J. Food Sci.2001, 66, 705-710. (29) Sirelkhatim, A.; Mahmud, S.; Seeni, A.; Kaus, N. H. M.; Ann, L. C.; Bakhori, S. K. M.; Hasan, H.; Mohamad, D. Review on Zinc Oxide Nanoparticles: Antibacterial Activity and Toxicity Mechanism. Nano-Micro Lett.2015, 7, 219-242. (30) Singh, S.; Lee, M. H.; Park, I.; Shin, Y.; Lee, Y. S. Antimicrobial Seafood Packaging: a Review. J Food Sci. Tech -Mysore 2016, 53, 2505-2518. (31) Slavin, Y. N.; Asnis, J.; Häfeli, U. O.; Bach, H. Metal Nanoparticles: Understanding the Mechanisms behind Antibacterial Activity. J. Nanobiotechg.2017, 15, 65. (32) Lefatshe, K.; Muiva, C. M.; Kebaabetswe, L. P. Extraction of Nanocellulose and In-situ Casting of ZnO/cellulose Nanocomposite with Enhanced Photocatalytic and Antibacterial Activity. Carbohyd. Polym.2017, 164, 301-308. (33) Martelli-Tosi, M.; Assis, O. B.; Silva, N. C.; Esposto, B. S.; Martins, M. A.; Tapia-Blácido, D. R. Chemical Treatment and Characterization of Soybean Straw and Soybean Protein Isolate/straw Composite Films. Carbohyd. Polym.2017, 157, 512-520.


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Ecofriendly and Biodegradable Soybean Protein Isolate Films

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