Tensile, water vapor barrier and antimicrobial properties of PLA/nanoclay composite films

PLA-based composite films with different types of nanoclays, such as Cloisite Na⁺, Cloisite 30B and Cloisite 20A, were prepared using a solvent casting method and their tensile, water vapor barrier and antimicrobial properties were tested. Tensile strength (TS), elongation at break (E), and water vapor permeability (WVP) of control PLA film were 50.45 ± 0.75 MPa, 3.0 ± 0.1%, and 1.8 × 10⁻¹¹ g m/m² s Pa, respectively. TS and E of nanocomposite films prepared with 5 g of clay/100 g of PLA decreased 10-20% and 11-17%, respectively, depending on the clays used. On the contrary, WVP of the nanocomposite films decreased 6-33% through nanoclay compounding. Among the clay types used, Cloisite 20A was the most effective in improving the water vapor barrier property while sacrificing tensile properties the least. The effect of clay concentration tested using Cloisite 20A showed a significant decrease in TS and WVP, with increases in clay content. Among the PLA/clay composite films tested, only PLA/Cloisite 30B composite film showed a bacteriostatic function against Listeria monocytogenes.     

Physical‐Mechanical Properties of Agar/κ‐Carrageenan Blend Film and Derived Clay Nanocomposite Film

Abstract: Binary blend films with different mixing ratio of agar and κ‐carrageenan were prepared using a solution casting method with and without nanoclay and the effect of their composition on the mechanical, water vapor barrier, and water resistance properties was tested. The tensile strength (TS) of the κ‐carrageenan film was greater than that of agar film. The water vapor permeability (WVP) of the agar film was lower than that of κ‐carrageenan film, the swelling ratio (SR) and water solubility (WS) of κ‐carrageenan film were higher than those of agar film. Each property of the binary blend films varied proportionately depending on the mixing ratio of each component. The XRD result indicated that the nanocomposite with agar/κ‐carrageenan/clay (Cloisite^® Na⁺) was intercalated. Consequently, the mechanical strength, water vapor barrier properties, and water contact angle (CA) were significantly (P < 0.05) improved through nanocomposite formation.     

Effect of PLA lamination on performance characteristics of agar/κ-carrageenan/clay bio-nanocomposite film

Multilayer films composed of PLA and agar/κ-carrageenan/clay (Cloisite® Na⁺) nanocomposite films were prepared, and the effect of lamination of PLA layers on the performance properties such as optical, mechanical, gas barrier, water resistance, and thermal stability properties was determined. The tensile strength (TS) of the agar/κ-carrageenan/clay nanocomposite films (67.8 ± 2.1 MPa) was greater than that of PLA films (43.3 ± 3.6 MPa), and the water vapor permeability (WVP), water uptake ratio (WUR), and water solubility (WS) of the nanocomposite films were higher than those of PLA films. The film properties of the multilayer films exhibited better properties of the component film layers. Especially, the WVP and water resistance of the bionanocomposite film were improved significantly, while the OTR of the PLA film decreased profoundly after lamination with PLA layers. Thermal stability of the bionanocomposite also increased after lamination with PLA layers.     

Effects of nano‐clay type and content on the physical properties of sesame seed meal protein composite films

Sesame seed meal protein (SSMP)/nano‐clay composite films were prepared, and the physical properties of the films were determined. The SSMP film was prepared with 5 g of SSMP and 2 g of glycerol in 100 mL of film‐forming solution, and the tensile strength (TS), elongation (E) and water vapour permeability (WVP) of the SSMP film were 2.51 MP, 21.84% and 3.23 × 10^?9 g m m^?2s^?1 Pa^?1, respectively. Two types of nano‐clays were incorporated to enhance the physical properties of the SSMP film. The TSs of the SSMP film with 5% Cloisite Na⁺ and 7% Cloisite 10A were 6.32 and 5.76 MPa, respectively, and the WVPs of the SSMP nanocomposite films were 2.04 × 10^?9 g m m^?2s^?1 Pa^?1 compared with the SSMP film without nano‐clay, which was 3.23 × 10^?9 g m m^?2s^?1 Pa^?1. Therefore, these results indicate that the SSMP nanocomposite film can be applied in food packaging.     

Physical properties of a composite film containing sunflower seed meal protein and its application in packaging smoked duck meat

Sunflower seed meal protein (SP) films were prepared using various plasticizers, cross-linking agents, Cloisite Na⁺ or red algae, and their physical properties, such as tensile strength (TS), elongation at break (E), and water vapor permeability (WVP) were determined. The TS, E, and WVP of the SP film containing sucrose and fructose (2:1) as a plasticizer and cinnamaldehyde as a cross-linking agent were 3.05 MPa, 34.42%, and 2.25 × 10⁻⁹ g m/m² s Pa, respectively. The incorporation of Cloisite Na⁺ improved the physical properties of the SP film. The TS of the SP/Cloisite Na⁺ composite film containing 3% Cloisite Na⁺ increased by 2.19 MPa, and the WVP of the composite film decreased by 0.52 × 10⁻⁹ g m/m² s Pa compared to the SP film. The incorporation of red algae also improved the TS of the SP film. The TS of the SP composite film containing 1.2% red algae increased by 3.82 MPa compared to the SP film. In addition, an SP/red algae composite film containing grapefruit seed extract (GSE) was prepared and used in food packaging. After 12 days of storage, the population of Listeria monocytogenes inoculated on smoked duck meats packed with the SP/red algae composite film containing 1.2% GSE decreased by 1.31 log CFU/g compared to the control packaging. Therefore, these results suggest that SP composite films can be prepared by the addition of red algae to the SP film–forming solution and that the SP/red algae composite film containing GSE can be used as an antimicrobial food packaging material.     

Effects of plasticizers and nano-clay content on the physical properties of chicken feather protein composite films

To prepare chicken feather protein (CFP)/nano-clay composite films and to evaluate the effects of various plasticizers and nano-clay concentrations on the mechanical properties of the films, CFP composite films with various concentrations of Cloisite Na⁺ were prepared, and their physical properties such as tensile strength (TS), elongation at break (E), and water vapor permeability (WVP) were investigated. Optimal CFP films were formed with 5 g of CFP, 0.5 g of glycerol, and 1.5 g of sorbitol in 100 mL of film-forming solution; the TS, E, and WVP of the film were 4.74 MPa, 10.08%, and 3.11 × 10⁻⁹ g m/m² s Pa, respectively. After the nano-clay was incorporated into the CFP film-forming solution, scanning electron microscopy and X-ray diffraction studies were conducted to examine the structural characteristics of the CFP/nano-clay composite films. The incorporation of nano-clay improved the physical properties of the CFP films. The TS of the CFP/nano-clay composite film containing 7% Cloisite Na⁺ increased by 1.21 MPa, and the WVP of the composite film decreased by 1.15 × 10⁻⁹ g m/m² s Pa compared to the CFP film. Therefore, these results suggest that CFP composite films can be prepared with improved mechanical property by the addition of nano-clay and used as a food packaging material in the food industry.     

Effects of nanoclay type on the physical and antimicrobial properties of PVOH-based nanocomposite films

Polyvinyl alcohols-based nanocomposite films with four types of montmorillonite (MMT) nanoclay, including 18-amino stearic acid (I.24TL), methyl, bis hydroxyethyl, octadecyl ammonium (I.34TCN), di-methyl, di-hydrogenated tallow ammonium/siloxane (I.44PSS) organically modified MMT and a natural MMT (Na⁺-MMT) were fabricated by a solution-intercalation, film-casting method, and effects of the nanoclays were evaluated on physical properties, including transmittance, tensile strength (TS), elongation at break (E), water solubility (WS), swelling ratio (SR), water vapor uptake ratio (WVUR), and water vapor permeability (WVP), as well as antimicrobial activity of the polyvinyl alcohols-based films. Transmittance, WS, SR, WVUR, WVP of the nanocomposite films were significantly reduced by nano-composition compared to a pure polyvinyl alcohols film. The WVP decreased by 11.8–20.7%, and WS, SR and WVUR decreased by 19.9–41.8%, 9.1–26.4%, and 4.8–12.8%, respectively. The extent of changes was dependent on nanoclay type. X-ray diffraction patterns revealed that intercalation was formed in nanocomposite films. Overall among all the tested nanoclays, Na⁺-MMT showed more impact on physical properties of polyvinyl alcohols films, and the polyvinyl alcohols film compounded with quaternary ammonium group displayed remarkable antimicrobial activity against Gram-positive bacteria.     

Physical and antimicrobial properties of Gelidium corneum/nano-clay composite film containing grapefruit seed extract or thymol

To improve the physical properties of Gelidium corneum (GC) film, Cloisite Na⁺ and 30B were incorporated into the preparation of the film. X-ray diffraction patterns of the films indicated that a degree of exfoliation and intercalation are formed depending on the type of nano-clays and its concentration and the film structure affects the physical properties of the GC/nano-composite films. Tensile strength (TS) of the GC film was increased by the addition of nano-clays. GC film had a TS of 19.59 MPa for the control, while the GC film having 3% Cloisite Na⁺ or 30B had TS of 27.37 and 26.40 MPa, respectively. Elongation at break and water vapor permeability were also improved by the addition of 3% nano-clays. The physical properties of the film were not improved by the addition of GSE or thymol, but the additions did inhibit the growth of Escherichia coli O157:H7 and Listeria monocytogenes. The results suggest that the nano-composite films containing GSE or thymol may extend the shelf life of food.     

Physical properties of a barley protein/nano‐clay composite film containing grapefruit seed extract and antimicrobial benefits for packaging of Agaricus bisporus

Barley protein (BP) was extracted from barley flour, and a BP film was prepared. To improve the physical properties of the BP film, nano‐clay was incorporated. Among the films prepared, the composite film containing 4% BP/1% Cloisite Na⁺ had the best physical property. The composite film containing grapefruit seed extract (GSE) was prepared and used as a packaging film for the button mushroom. Packing of the mushroom with this film inhibited microbial growth during storage. After 7 days of storage, packaging of mushrooms with the film containing 0.7% GSE reduced the populations of total aerobic bacteria and yeast and moulds by 0.95 and 0.58 log CFU/g, respectively, compared with the control. These results suggest that the BP/Cloisite Na⁺ film containing GSE can be used as an environment‐friendly packaging for maintaining mushroom quality during storage.     

Effects of various plasticizers and nanoclays on the mechanical properties of red algae film

To manufacture red algae (RA) film, we used various plasticizers such as glycerol, sorbitol, sucrose, fructose, and polypropylene glycol (PPG), and then determined the mechanical properties of the RA films. The tensile strength (TS), elongation at break (E), and water vapor permeability (WVP) of the films containing various plasticizers ranged between 0.43 to 9.10 MPa, 10.93% to 47.17%, and 1.28 to 1.42 ng m/m2sPa, respectively. RA films containing fructose as a plasticizer had the best mechanical properties of all the films evaluated. Incorporation of nanoclay (Cloisite Na+ and 30B) improved the mechanical properties of the films. RA film with 3% Cloisite Na+ had a TS of 10.89, while RA film with 30B had a TS of 10.85 MPa; these films also had better E and WVP values than the other RA films evaluated. These results suggest that RA/nanoclay composite films are suitable for use as food packaging materials. PRACTICAL APPLICATION: Edible RE/nanoclay composite films prepared in the present investigation can be applied in food packaging.     

Properties of Bio-nanocomposite Films from Tilapia Skin Gelatin as Affected by Different Nanoclays and Homogenising Conditions

Fish gelatin films incorporated with hydrophilic and hydrophobic montmorillonite (mmt) nanoclays with the aid of homogenisation using different pressure levels (1,000 to 4,000 lb/in²) and passes (two and four) were characterised. Young’s Modulus, tensile strength and elongation at break of films decreased with increasing pressure levels and number of passes. High pressure homogenisation generally lowered the mechanical properties of nanocomposite films. Additionally, water vapour barrier property became poorer, when high pressure homogenisation was implemented. Films incorporated with hydrophobic nanoclay (Cloisite 20A) exhibited the lower water vapour permeability (WVP) than those with hydrophilic nanoclay (Cloisite Na⁺). Colour parameters (L*, a*, b* and ?E*) of nanocomposite films were affected to some degrees by homogenisation conditions. Transparency of films increased when homogenisation pressure and number of passes increased. As revealed by wide angle X-ray diffraction (WAXD) analysis, nanocomposite films prepared using homogenisation had exfoliated nanostructure, whilst those prepared without homogenisation exhibited intercalated nanostructure. Thermogravimetric (TGA) and differential scanning calorimetric (DSC) analyses indicated that thermal stability of nanocomposite films varied with homogenisation condition, being higher in these films than in those without nanoclay. Thus, homogenisation condition and hydrophobicity of nanoclay directly affected the properties of nanocomposite films from fish skin gelatin.     

Original article: Use of nano‐clay (Cloisite Na+) improves tensile strength and vapour permeability in agar rich red algae (Gelidium corneum)–gelatin composite films

In this study, we aimed to improve the physical properties of Gelidium corneum–gelatin (GCG) film by including nano‐clay in the film‐forming solution and tested the antimicrobial properties of the thymol‐containing composite film as a packaging material for chicken breast. Addition of nano‐clay improved the physical properties of GCG film. The tensile strength of the GCG film containing 1% Cloisite Na⁺ was 38.13 MPa, compared to the 26.65 MPa for the GCG film. The water vapour permeability of the GCG film was 3.56 ng m m^?2sPa, while that of the GCG film with 1% Cloisite Na⁺ was 3.24 ng m m^?2sPa. Incorporation of thymol into the film had its antimicrobial activities against Escherichia coli O157:H7 and Listeria monocytogenes. When used to pack chicken breast, the GCG/nano‐clay film containing thymol inhibited microbial growth during storage.     

Properties of low methoxyl pectin‐carboxymethyl cellulose based on montmorillonite nanocomposite films

In this study, the low methoxyl pectin‐carboxymethyl cellulose‐based montmorillonite (LMP‐CMC‐MMT, LCM) nanocomposite films with nine ratios of LMP:CMC (from 10:0 to 0:10) and different MMT contents (1–8 wt%) were prepared. The mechanical properties, colour, opacity and water vapour permeability (WVP) of composite films were investigated. The maximum of tensile strength (TS) of composite films was 39.85 ± 2.51 MPa at LMP:CMC ratio of 4:6 and 4 wt% MMT (LCM47), which indicated the formation of hydrogen bonds between MMT and LMP‐CMC. The reduction of WVP of the LCM47 composite film was 333% of that of the CMC film due to the tortuous path caused by MMT incorporation. LCM composite films had the higher b*‐ and ΔE*‐values and lower L*‐values in comparison with LMP‐CMC (LC) composite films. The LCM composite films showed a decrease in transparency as MMT content increased.     

Effect of structural characteristics of modified waxy corn starches on rheological properties,film‐forming solutions,and on water vapor permeability,solubility, and opacity of films

Waxy corn starch (amylopectin) and three of its chemical derivatives: acetylated cross‐linked (ACLS), oxidized (OS), and octenyl‐succinylated (OSA), were used together with additives such as Tween 80, sorbitol, and beeswax suspension or safflower oil to test their effect on film‐forming solutions (FFS) and films. The objectives of this study were the starch structure characterization, and its correlation with rheological properties of FFS and solubility, opacity, and water vapor permeability (WVP) of the produced films. Analysis of starch structure, rheological characterization, and films micrographs revealed that the starches contained predominantly low MW amylopectin molecules and film properties depended on their ability to reorganize. Additionally, the interaction among groups introduced in modified starches or with additive molecules can hinder or promote starch reorganization, resulting in films with increased or reduced WVP, solubility and transparency properties. Films were obtained by casting and showed a thickness less than 41 µm. Films prepared with OS and beeswax exhibited the best reorganizing capacity of FFS, resulting in less soluble (30.0 ± 1.6%), highly transparent (23.2 ± 3.3 UA × nm) and less permeable films (0.485 ± 0.016 g · mm · m⁻² · h⁻¹ · kPa⁻¹). On the other hand, ACLS showed an opposite trend which was attributed to a more open film structure. These results contribute to understand the molecular interactions of waxy starch molecules in FFS which may be useful to design tailored coatings.     

Effect of Type and Content of Modified Montmorillonite on the Structure and Properties of Bio-Nanocomposite Films Based on Soy Protein Isolate and Montmorillonite

Abstract: The nonbiodegradable and nonrenewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). Bio-nanocomposite films based on soy protein isolate (SPI) and modified montmorillonite (MMT) were prepared using melt extrusion. The effect of different type (Cloisite 20A and Cloisite 30B) and content (0% to 15%) of modified MMT on the structure (degree of intercalation and exfoliation) and properties (color, mechanical, dynamic mechanical, thermal stability, and water vapor permeability) of SPI-MMT bio-nanocomposite films were investigated. Extrusion of SPI and modified MMTs resulted in bio-nanocomposites with exfoliated structures at lower MMT content (5%). At higher MMT content (15%), the structure of bio-nanocomposites ranged from intercalated for Cloisite 20A to disordered intercalated for Cloisite 30B. At an MMT content of 5%, bio-nanocomposite films based on modified MMTs (Cloisite 20A and Cloisite 30B) had better mechanical (tensile strength and percent elongation at break), dynamic mechanical (glass transition temperature and storage modulus), and water barrier properties as compared to those based on natural MMT (Cloisite Na⁺). Bio-nanocomposite films based on 10% Cloisite 30B had mechanical properties comparable to those of some of the plastics that are currently used in food packaging applications. However, much higher WVP values of these films as compared to those of existing plastics might limit the application of these films to packaging of high moisture foods such as fresh fruits and vegetables.     

还原剂影响可食性大豆分离蛋白膜性能的研究

研究了还原剂对可食性大豆分离蛋白 (SPI)膜性能的影响。结果表明 ,还原剂可明显提高SPI膜的抗拉强度 (TS) ,降低水蒸气迁移系数 (WVP) ,但伸长率 (E)有所下降。添加还原剂的SPI膜在 pH 7时机械强度和阻隔性最好 ,其中添加半胱氨酸的SPI膜 TS最大 ,为14.4 8MPa ,WVP最小 ,为 4 .6 1g·mm/m2 ·d·kPa     

Effects of lipids on mechanical and moisture barrier properties of edible gellan film

Beeswax or a 1:1 blend of stearic–palmitic acids (S–P) were incorporated into gellan films through emulsification to form gellan/lipid composite films. The films, containing 0–25% lipid (dry film basis) were examined for mechanical properties, water vapor permeability (WVP) and opacity. Addition of the lipids to gellan films significantly improved the WVP (P<0.05), but lowered the mechanical properties and caused the films to become opaque. Beeswax was more effective than S–P acids in reducing the WVP, and films with beeswax showed better mechanical properties overall than those with S–P acids. The tensile properties of gellan films containing 14.3% beeswax were evaluated as a function of water activity (a_w) of the film. Increasing the a_w decreased the tensile strength (TS) and elastic modulus but tensile elongation was not affected. The extent of the decreases in TS for the composite film was less pronounced than that for a similar film without lipids, suggesting that lipids help to alleviate moisture sensitivity of gellan films.     

Physicochemical and Engineering Properties of Nanocomposite Films Based on Chitosan and Pseudoboehmite Alumina

Chitosan-based nanocomposite plastic films were developed by adding 0, 1, 3, and 5 % boehmite alumina (BAH) nanoparticles as a percentage of chitosan powder weight. The films were cast via solution. The effect of BAH content on the physicochemical and engineering properties of the resultant films were determined. The swelling, water vapor adsorption capacity, and transparency were significantly reduced with increased BAH content. The stability of the films against microbial degradation under high relative humidity also increased with BAH content. The water vapor permeability (WVP) reduced with increased temperature giving rise to negative activation energy values, which ranged between 2.08 and 3.36 kJ/mol. However, at constant temperature, inclusion of BAH did not have significant effect on water vapor permeability (WVP). WVP was predicted to high accuracy (r ²?=?0.984) using a full quadratic regression model. All the films had similar tensile and thermal behaviors. The implications of the findings are discussed based on prospective applications of the biodegradable film especially for fresh produce packaging.     

Preparation and characterization of kafirin‐quercetin film for packaging cod during cold storage

This study mainly evaluated the physical properties of kafirin‐quercetin (KQ) edible films and their application on the quality of cod fillets during cold storage. The results showed that the addition of quercetin significantly increased mechanical properties of KQ films, while decreased water vapor permeability, water solubility, and transparency. As quercetin was 0.4% (wt/vol), the film had the highest tensile strength (4.96 ± 1.23 MPa), the lowest water vapor permeability (1.08 ± 0.09 g·mm·m^?2·h·KPa^?1) and water solubility (22.02 ± 0.45%). Moreover, compared with the pure kafirin and polythylene films, KQ films could effectively inhibit the cod meat deterioration by restraining the growth of microorganisms and decreasing TVB‐N and TBARs. The KQ_0.4% film was the best to prolong the shelf life of cod fillets during cold storage. Therefore, KQ edible films could be used as a potential food packaging material to protect and retain the quality of aquatic products.     

Edible Films and Coatings from Soy Protein

A method was developed by which films could be prepared from commercial isolated soy protein (ISP). ISP was treated with alkali (ATISP) to alter film orooerties. Water vapor oermeability (WVP). oxygen‘permeability (O₂P), tensile strength (TS), percent elongatidn (%E), and appearance of ISP and ATISP were compared. Alkali treatment had no effect on WVP. O₂P, and TS, gave hieher %E, and improved film appearance. Films properties were also compared at pH 6, 8, 10, and 12. In general, pH 6 gave higher WVP and O₂P and lower TS and %E; while higher pH gave lower WVP and O₂P and higher TS and %E. ATISP films could not be produced at pH 6. Film appearance generally improved with increased pH.