Evaluation of Edible, Bilayer Films for Use as Moisture Barriers for Food

Two edible, bilayer films, consisting of methylcellulose (MC) and polyethylene glycol 400 in the hydrocolloid layer, and beeswax, either applied molten (Wax-M film) or from an ethanol solution (Wax-S film), in the lipid layer, were evaluated as barriers to water vapor (WV) after abusive tests. The Wax-M film maintained its WV barrier properties better than the Wax-S film after mechanical abuse. The Wax-M film was also evaluated as a moisture barrier when formed-in-place on the surface of brownies. When brownies were stored at 100% relative humidity and 25°C, the Wax-M film significantly (P < 0.05) decreased moisture absorption as compared to that of control samples.     

Preparation and characterization of agar/clay nanocomposite films: the effect of clay type

Abstract: Agar‐based nanocomposite 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 agar film were 29.7 ± 1.7 MPa, 45.3 ± 9.6%, and (2.22 ± 0.19) × 10^?9 g·m/m²·s·Pa, respectively. All the film properties tested, including transmittance, tensile properties, WVP, and X‐ray diffraction patterns, indicated that Cloisite Na⁺ was the most compatible with agar matrix. TS of the nanocomposite films prepared with 5% Cloisite Na⁺ increased by 18%, while WVP of the nanocomposite films decreased by 24% through nanoclay compounding. Among the agar/clay nanocomposite films tested, only agar/Cloisite 30B nanocomposite film showed a bacteriostatic function against Listeria monocytogenes.     

Preparation of biopolymer film from chitosan modified with lipid fraction

Films formed from polysaccharides, as chitosan, present a high permeability in water vapour. In order to increase resistance to water vapour for chitosan‐based films, different lipid fractions were incorporated into a filmogenic matrix: fish and vegetable oils, stearic and oleic acids. The chitosan showed a molecular weight of 150 kDa and a deacetylation degree of 86 ± 1%. Results showed that incorporation of different lipid fractions decreased the water vapour permeability (WVP) (1.3–1.8 g mm m^?2 day^?1 kPa^?1) as compared with pure chitosan film (3.8 g mm m^?2 day^?1 kPa^?1). A higher reduction in WVP (65%) was found with the addition of refined fish oil to the continuous matrix of the films than with the addition of refined rice oil, oleic or stearic acid (50–60%). However, pure chitosan films showed better tensile strength (TS = 33 MPa) and elongation percentage (E = 18%) than lipids fraction–chitosan films (7–19 MPa and 7–13%, respectively).     

Water barrier and physical properties of starch/decolorized hsian-tsao leaf gum films: Impact of surfactant lamination

The moisture barrier and physical properties of bilayer films prepared by lamination of starch/decolorized hsian-tsao leaf gum (dHG) and surfactant layers were investigated. It was found that the water vapor permeability (WVP) of tapioca starch/dHG film (1.31 × 10^?10 g/m s Pa) pronouncedly decreased by the aid of a surfactant layer lamination (1.36–5.25 × 10^?12 g/m s Pa). The WVP of bilayer film increased with increasing the concentration of starch/dHG in the surfactant layer, but was not significantly influenced when it was thickened. The sorption isotherms of both monolayer and bilayer films made from starch/dHG showed typical behavior of water-vapor-sensitive hydrophilic biopolymers. However, the equilibrium moisture content of the monolayer film was significantly higher than that of bilayer films when water activity (a_w) reaches 0.33. Both the tensile and puncture force of starch/dHG films did not vary significantly by laminating a surfactant layer, indicating the mechanical strength of surfactant layer is relatively weak, and this surfactant layer mainly served as a barrier for moisture. When compared to emulsion-based starch/dHG films with surfactant, the surfactant laminated starch/dHG films showed higher water barrier property, mechanical strength, and transparency.     

Mechanical and Barrier Properties of Edible Chitosan Films as affected by Composition and Storage

Oxygen permeability coefficients (OP), water vapor permeability coefficients (WVP), ethylene permeability coefficients (EP), tensile strength (TS) and percent elongation (%E) at break values were determined for chitosan films plasticized with glycerin at two concentrations (0.25 and 0.50 mL/g chitosan). Film samples were tested after 0, 2, 4, 8 and 12 wk of storage. After an initial drop in permeability during the first 2 wk of storage, mean OP (4.6 × 10^?5 cc/m-day-atm) and mean EP (2.3 × 10^?4 cc./m.day.atm) remained constant while mean WVP (2.2 × 10^?1 g/m-day-atm) decreased with respect to storage time. TS values (15–30 MPa) decreased and %E values (25%–45%) increased with respect to storage time. The stability of OP and EP values with storage was not expected, while the change in mechanical properties was as expected.     

Liquid and vapour water transfer through whey protein/lipid emulsion films

BACKGROUND: Edible films and coatings based on protein/lipid combinations are among the new products being developed in order to reduce the use of plastic packaging polymers for food applications. This study was conducted to determine the effect of rapeseed oil on selected physicochemical properties of cast whey protein films. RESULTS: Films were cast from heated (80 °C for 30 min) aqueous solutions of whey protein isolate (WPI, 100 g kg^?1 of water) containing glycerol (50 g kg^?1 of WPI) as a plasticiser and different levels of added rapeseed oil (0, 1, 2, 3 and 4% w/w of WPI). Measurements of film microstructure, laser light‐scattering granulometry, differential scanning calorimetry, wetting properties and water vapour permeability (WVP) were made. The emulsion structure in the film suspension changed significantly during drying, with oil creaming and coalescence occurring. Increasing oil concentration led to a 2.5‐fold increase in surface hydrophobicity and decreases in WVP and denaturation temperature (T_max). CONCLUSION: Film structure and surface properties explain the moisture absorption and film swelling as a function of moisture level and time and consequently the WVP behaviour. Small amounts of rapeseed oil favourably affect the WVP of WPI films, particularly at higher humidities. Copyright © 2010 Society of Chemical Industry     

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.     

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.     

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.     

Effects of glycerol,sorbitol, xylitol and fructose plasticisers on mechanical and moisture barrier properties of pullulan–alginate–carboxymethylcellulose blend films

The effects of glycerol, sorbitol, xylitol and fructose plasticisers on water sorption, mechanical properties, water vapour permeability (WVP) and microstructure of pullulan–alginate–carboxymethycellulose (PAC) blend films were investigated. At low plasticiser concentrations (below 7% w/w dry basis), antiplasticisation effect was observed, causing an increase in tensile strength (TS) but a decrease in the equilibrium moisture content. As glycerol concentration increased from 0% to 7%, TS increased from 68.1 to 69.6 MPa, whereas equilibrium moisture contents at 0.84 a_w decreased from 0.37 to 0.3 g H₂O g^?1 dry basis. At higher plasticiser concentrations (14–25% w/w), an opposite trend was observed on the PAC films, resulting in the reduction of TS and elevation of moisture content. Among the four plasticisers tested, the fructose‐plasticised films were the most brittle, showing the highest TS, but had the lowest elongation at break (EAB), WVP and equilibrium moisture content values than films plasticised with other polyols. On the other hand, glycerol resulted in the most flexible film structure, exhibiting opposite materials' properties as compared with the fructose‐plasticised films. For instance, at 25% (w/w) plasticiser concentration, EAB and WVP values of fructose‐plasticised films were 33.5% and 3.48 × 10^?6 g m Pa^?1 h^?1 m^?2, which were significantly lower than that of glycerol‐plasticised films (58.6% and 4.86 × 10^?6 g m Pa^?1 h^?1 m^?2, respectively). Scanning electron microscopy showed that the plasticised PCA films were less homogeneous and more porous than the unplasticised counterparts, indicating that plasticisers had an effect on the microstructural morphology of the film matrix.     

Water Vapor Permeability of an Edible, Fatty Acid, Bilayer Film

A bilayer film consisting of stearic and palmitic acids as one layer and hydroxypropyl methylcellulose as the other was prepared. The permeability of this film to water vapor was tested under a variety of conditions involving film composition, temperature and relative humidity. This film exhibited permeability values (g · mil w m⁻²· day⁻¹· mm Hg⁻¹) of 0.5 at 40°C 0.3 at 25°C 1.7 at 5°C, and 6.0 at −19°C. This film would be expected to perform well at relative humidities below 90% and temperatures within the range of 40°C to -19°C.     

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 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.     

Properties of MTGase treated gluten film

Water barrier and mechanical properties of gluten film affected by the treatment of microbial transglutaminase (MTGase) were evaluated with the water vapor permeability (WVP), magnetic resonance imaging (MRI) T₂ map and mechanical properties of gluten films. The water barrier ability of gluten films was superior to the no film but inferior to the Parafilm^® investigated by MRI T₂ maps in a two-gelatin-gel system. The WVP of gluten film increased, while the tensile force decreased, with increasing in the dosage of MTGase treated. The gluten films were also dyed with Acid Fuchsin and observed by a confocal laser scanning microscopy (CLSM) to localize the proteins in the film. The micrographs showed many pores and inhomogenous gluten network in MTGase treated gluten films. High WVP and weak mechanical properties of MTGase treated gluten films were attributed to the cross-link bonds formation, which created pores and inhomogenous gluten matrix as evidenced by CLSM.     

Effect of temperature,pH and film thickness on nisin release from antimicrobial whey protein isolate edible films

BACKGROUND: An active packaging film based on whey protein isolate (WPI) was developed by incorporating nisin to promote microbial food safety. The effect of temperature and pH on the release of nisin from edible films of different thickness was investigated. The film mechanical properties and inhibitory effect were also evaluated. RESULTS: Nisin release was significantly favoured by low pH, with the highest release after 24 h (1325 IU), which was not significantly affected by temperature (5 or 10 °C). Thickness significantly affected film elongation, with thicker films showing the highest elongation (54.3 ± 2.7%). Water vapour permeability (0.15 ± 0.4 g mm m^?2 kPa^?1 h^?1) and elastic modulus were not significantly affected by thickness. The highest nisin effective diffusivity (5.88 × 10^?14 m² s^?1) was obtained using a solution at pH 4, 112 µm film thickness and a temperature of 5 °C. More than four log cycles of Brochotrix thermosphacta were reduced from the surface of a ham sample after 8 days of incubation at 4 °C by the active WPI film containing 473 IU cm^?2 nisin. CONCLUSION: Nisin diffusivity from WPI edible films was favoured at lower pH and film thickness. This active packaging film may be used to preserve the quality and safety of meat products. Copyright © 2009 Society of Chemical Industry     

Physicochemical,Antioxidant, In Vitro Release,and Heat Sealing Properties of Fish Gelatin Films Incorporated with β-Cyclodextrin/Curcumin Complexes for Apple Juice Preservation

The antioxidant activity of gelatin film is poor. Curcumin is a natural antioxidant, but its main disadvantage is low aqueous solubility. In this study, curcumin was encapsulated by β-cyclodextrin to prepare βCD/CUR complex. Gelatin films incorporated with βCD/CUR complexes (GL-βCD-CUR films) were fabricated. The effects of curcumin content on their properties were investigated. Results showed that the water solubility of curcumin was improved in βCD/CUR complex. The βCD/CUR complex containing 2.5 mg curcumin had smaller size and more homogeneous distribution. The thicknesses of all films were about 87 μm and there were no significant differences (p > 0.05). The optimal tensile strength (TS) and elongation at break (EAB) of GL-βCD-CUR films were observed at the curcumin content of 2.5 mg. With the increase of curcumin concentration, water vapor permeability (WVP) of gelatin-based films decreased from 2.88 to 2.38 × 10^?10 g m^?1 Pa^?1 s^?1 and water content (WC) decreased from 34.64 to 24.72%, but water solubility (WS) increased from 21.22 to 59.75%. GL-βCD-CUR films exhibited lower light transmission in UV light compared with GL-βCD film. SEM provided that there was a good compatibility between gelatin molecules and βCD/CUR complexes. FTIR proved that no functional groups appeared or disappeared. A significant increase in antioxidant activity and the stability of this activity along with a lower release rate of curcumin in food simulant were observed in gelatin films incorporated with βCD/CUR complexes. The heat sealing property of GL-βCD-CUR films containing 1 or 2.5 mg curcumin was better than that of film containing 5 mg curcumin. The L values of red Fuji (Malus pumila mill) apple juice packed by GL-βCD-CUR films reduced slowly. The slowest decline in total polyphenol content was found in GL-βCD-2.5CUR group. Our results indicated that the incorporation of βCD/CUR complex significantly enhanced the antioxidant activity of gelatin film, and the GL-βCD-CUR film can be used in apple juice preservation.     

Effect of plasticizer content on the functional properties of extruded gelatin-based composite films

Beef gelatin, in combination with varying levels of glycerol, was used to manufacture films by extrusion. A twin-screw co-rotating extruder was employed to produce the films and the mechanical and barrier properties of the films were investigated. Increasing the plasticizer content increased (P < 0.05) elongation at break (EAB) values but decreased (P < 0.05) tensile strength (TS) values. Oxygen permeability (OP) values for gelatin-based composite films increased (P < 0.05) as the concentration of glycerol increased. Additionally, the solubility of films in water and seal strength increased as glycerol content increased. FTIR results indicated that increasing glycerol concentration increased and displaced the peak situated around 1032 cm⁻¹, which corresponded to glycerol. Gelatin-based composite films with a concentration of 0.2% glycerol possessed the lowest water vapor permeability (WVP) and OP values. From the data generated in this study, it is clear that the use of a plasticizing agent in film formulations should be carefully considered because of the negative effects that the plasticizing agent could have on extruded film barrier properties.     

The Evaluation of Mechanical,Thermal, Optical and Microstructural Properties of Edible Films with Solid Lipid Nanoparticles-Xanthan Gum Stored at Different Temperatures and Relative Humidities

Solid lipid nanoparticles (SLN) were obtained using the hot homogenization method and incorporated into a xanthan gum matrix (XG) to prepare edible films. The effects of SLN content (60, 65, 70, and 75 g/L) on the mechanical, color, thermal and microstructural properties, and water vapor permeability (WVP) were studied. The SLN film-forming systems remained stable for 7 weeks. Particle size was in the range of 222–257 nm. The mechanical properties of the films improved significantly when the SLN were introduced into the polymeric network to provide greater strength and flexibility with elongation at breaking of 2–9 %, affected by temperature (4–25 °C), SLN concentration (60–75 g/L), and relative humidity (60–90 %). WVP was lower when edible films based on XG were incorporated with SLN at values of 0.50–0.70 g m-2 h-1 kPa^?1. The distribution of the SLN in the XG matrix was observed under scanning electron microscopy and showed changes in the arrangement as a function of SLN concentration. This explains the positive effect on the properties of the film of SLN-XG at 60 and 65 g/L. Total color difference (ΔE) increased with SLN content at values of 3.5–14. Thermal analysis showed that higher SLN content increased the melting temperature, while the plasticizer reduced it.     

Mechanical properties and water vapour permeability of hydrolysed collagen–cocoa butter edible films plasticised with sucrose

The aim of this study was to develop and characterise edible films produced from hydrolysed collagen and cocoa butter and plasticised with sucrose. The mechanical properties, water vapour permeability, opacity and morphology of the films were characterised. The film composition that yielded the best results was used to produce a coating for application in chocolate panned products. A water-based coating with desirable barrier properties that could replace shellac is important for the environment as well as health, and also because chocolate products have great appeal among children. The films obtained were easily manageable and flexible. Sucrose reduced tensile strength (TS), while hydrolysed collagen at concentrations above 15% increased it. Cocoa butter resulted in less-resistant films. The elongation at break values (EAB%) were higher for films containing higher sucrose concentrations. The water vapour permeability (WVP) ranged from 0.32 to 0.63 g mm m⁻² h⁻¹ kPa⁻¹. For the same concentration of cocoa butter, the WVP was directly affected by the thickness of the film, i.e., the greater the thickness, the higher the WVP. Cocoa butter increased film opacity, while sucrose decreased it, particularly at concentrations above 17.5%. High concentrations of hydrolysed collagen produced films with more homogeneous surfaces. The brightness of the product with the coating developed in this study was attractive; however the brightness of the product with shellac was considered more intense. The properties of these films indicate that they are promising systems for coating chocolate panned products.     

Development and characterization of cassava starch and soy protein concentrate based edible films

The sensory attributes, mechanical, water vapour permeability (WVP) and solubility properties of cassava starch and soy protein concentrate (SPC)‐based edible films of varying levels of glycerol were studied. Addition of SPC and glycerol up to 30% and 20%, respectively, reduced stickiness and improved colour and appearance of the films. Tensile strength (TS), elastic modulus (EM) and elongation at break (EAB) of films increased, while film solubility (FS) and WVP decreased with SPC and glycerol up to 50% and 20% level, respectively, ranging from 20.33 to 26.94 MPa (TS), 41.33 to 72.76 MPa (EM), 7.90 to 12.28 MPa (EAB), 15.07 to 31.90% (FS) and 2.62 to 4.13 g H₂O mm m^?2 day kPa (WVP). The TS, EAB and WVP were higher for the biofilms than for low‐density polyethylene and cellophane films.