Mechanical and barrier properties of biodegradable soy protein isolate-based films coated with polylactic acid

Polylactic acid (PLA)-coated soy protein isolate (SPI) films were prepared by dipping SPI film into PLA solution. The effects of coating on improvements in mechanical and water barrier properties of the film were tested by measuring selected film properties such as tensile strength (TS), elongation at break (E), water vapor permeability (WVP), and water solubility (WS). TS of SPI films increased from 2.8±0.3 up to 17.4±2.1 MPa, depending on the PLA concentration of the coating solution, without sacrificing the film's extensibility. In contrast, the extensibility of SPI film coated with solution containing more than 2 g PLA/100 ml solvent, increased. WVP of PLA-coated SPI films decreased from 20 to 60 fold, depending on the concentration of PLA coating solution. Water resistance of SPI films was greatly improved as demonstrated by the dramatic decrease in WS for PLA-coated films. The improvement in water barrier properties was mainly attributed to the hydrophobicity of PLA.     

Tensile and water vapour properties of calcium‐crosslinked alginate‐cashew tree gum films

In this study, sodium alginate films were blended with cashew tree gum (CTG) and immersed in CaCl₂ solution. The influence of CTG concentration and immersion time in CaCl₂ on tensile properties, water vapour permeability and water solubility (WS) of alginate films was evaluated. Glycerol‐plasticized alginate/CTG films were cast on glass plates, which were then immersed in a 2% CaCl₂ solution to crosslink alginate. CTG concentration in the film solution and immersion time in CaCl₂ bath were varied according to a central composite design. Tensile strength, Young′s modulus, WS and water vapour barrier of the films were favoured by higher immersion times in CaCl₂ and lower CTG concentrations. The negative CTG effects on such properties have been attributed to competition between the polysaccharides for interactions with calcium ions, reducing crosslinking density and loosening the film structure. On the other hand, this loosening effect resulted in higher film flexibility at higher CTG concentrations.     

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.     

Influence of CaCl2 on the water vapor permeability and the surface morphology of mesquite gum based edible films

Oil-in-water (O/W) emulsions with a dispersed phase mass fraction (φ_m) of 0.175 were prepared by dispersing a blend of candelilla wax/mineral oil (2:1 ratio) in 10 g of mesquite gum per 100 g of water containing either CaCl₂ (0.0, 0.1, 0.2, 0.3, 0.4 or 0.5 g) alone or combined with 1.5 g of glycerol. The mean volumetric droplet size (d_3,0), the rate of droplet coalescence (C) and the viscosity-shear rate behavior of the emulsions were affected by the addition of CaCl₂ alone or combined with glycerol. The Carreau-Yasuda model fitted best the viscosity-shear rate data of all the emulsions. The surface morphology of the edible films, analyzed by Atomic Force Microscopy (AFM), exhibited a strong dependence on the CaCl₂ concentration. Maximum roughness occurred with a CaCl₂ concentration of 0.3 g per 100 g. Films with glycerol showed significantly higher roughness than those with only CaCl₂. Water vapor permeability (WVP) was significantly lowered as the concentration of CaCl₂ increased from 0.1 to 0.3 g per 100 g in the coatings, but increased again at CaCl₂ concentrations of 0.4-0.5 g per 100 g. Coatings containing glycerol displayed significant higher WVP.     

Heat Curing of Soy Protein Films at Selected Temperatures and Pressures

Vacuum and temperature effects on moisture content, water vapor permeability (WVP), color (L, a, b, and ΔE), tensile strength (TS), elongation (E), and total soluble matter (TSM) of soy protein isolate (SPI) films were examined. SPI films were cured at 60, 72.5, or 85 °C and at 101.3, 81.32, or 61.32 kPa for 24 h. As a result of heat-curing moisture content, WVP, E, and TSM decreased, and total color difference and TS increased. Pressure, individually and interactively with temperature, significantly affected film moisture content, TS, and TSM.     

Development and characterization of a novel biodegradable edible film obtained from psyllium seed (Plantago ovata Forsk)

In this study, the physical, thermal and mechanical properties of a novel edible film based on psyllium hydrocolloid (PH) were investigated. PH films were prepared by incorporation of three levels of glycerol (15%, 25%, and 35% w/w). As glycerol concentration increased, water vapor permeability (WVP), percent of elongation (E%) and water solubility of PH films increased whilst, tensile strength (TS), surface hydrophobicity and glass transition point (T_g) decreased significantly. At the level of 15% (W/W) of glycerol, PH films showed the lowest WVP values (1.16 × 10⁻¹⁰ g H₂O m⁻² s⁻¹ MPa⁻¹), E% (24.57%) and water solubility (47.69%) and the highest values for TS (14.31 MPa), water contact angle (84.47°) and T_g (175.2 °C). By increasing glycerol concentration, PH films became slightly greenish and yellowish in color but still transparent in appearance. This study revealed that the psyllium hydrocolloid had a good potential to be used in producing edible films with interesting specifications.     

Migration analysis,antioxidant, and mechanical characterization of polypropylene-based active food packaging films loaded with BHA,BHT, and TBHQ

Polypropylene (PP) based active composite films were prepared by adding butylated hydroxy anisole (BHA), butylated hydroxytoluene (BHT), and tertiary butylated hydroquinone (TBHQ) antioxidants using the extrusion molding process. All concentrations of BHT, 2% to 3% BHA, and 3% TBHQ significantly increased the tensile strength (TS) of the composite films compared with control films. Increasing antioxidant concentration decreased TS values for BHT films, whereas an opposite trend was observed for BHA and TBHQ films. BHA at < 2%, BHT at > 2%, and TBHQ at all added concentrations significantly reduced elongation at break (E_b) of the composite films compared to control films. Water vapor permeability (WVP) of 1% BHT film was not significantly different from control. However, other antioxidants especially at increased concentrations significantly increased WVP values. TBHQ films with 300% to 662% increase had the highest WVP and BHT films with 5% to 81% increase had the lowest WVP among composite films. All three antioxidants had a negative effect on the transparency of the films; however the effect of BHA at higher concentrations was greater. The antioxidants did not change the color attributes of the films. Films containing all antioxidants showed 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity, which increased with increase in their concentration, especially for those containing 3 wt.% BHT and TBHQ. Overall, incorporating BHA and BHT into a PP matrix improved mechanical, barrier, antioxidant properties, and film appearance and consequently were proposed for the development of antioxidant active PP films. TBHQ film is not recommended for food packaging because of its weak mechanical properties (lower E_b and TS values, higher WVP, and greater migration).     

Properties of triticale flour protein based films

Triticale flour proteins based films were developed. Solubility in water, water vapor permeability (WVP), and mechanical properties of triticale films are presented. The effects of thermal treatments and glycerol concentration were also evaluated. WVP values were in the range 0.10-4.22 × 10⁻¹⁰ g m⁻¹ s⁻¹ Pa⁻¹. Tensile strength (TS) and percentage of elongation (%E) were in the range 2.9-0.20 MPa and 250-110% respectively. Total soluble matter (TSM), WVP, and %E decreased with the increase in the curing temperature. More plasticized films presented greater TSM, WVP, %E and lower values of TS. At a giving temperature (T) and glycerol concentration, an increase in relative humidity (RH) resulted in higher values of TSM, WVP, %E and lower TS values. It was observed that in films with the same treatments and conditioning, WVP increased with the increase in measurement temperature. Triticale proteins showed suitable film-forming capacity for the formulation of biodegradable films.     

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.     

Water resistance and mechanical properties of biopolymer (alginate and soy protein) coated paperboards

The effect of biopolymer coating on the water barrier and mechanical properties of paperboards used as corrugated fiberboard box liners was studied under several conditions. Paperboards were coated with selected biopolymers, such as alginate and soy protein isolate (SPI) and studied with or without further treatment, such as cross-linking through CaCl₂ or formaldehyde treatment and compositing with organically modified montmorillonite (OMMT). Biopolymer coating increased the thickness of paperboards from 9% to 16%, depending on the coating materials and treatment methods, and resulted in a smoother and more homogeneous surface. Though the tensile strength (TS) of the coated paperboards decreased from 12.5% to 37.5% of the uncoated paperboards by coating, ring crush strength was not decreased. Wetting properties, such as contact angle of water drop, dynamic change in contact angle, water vapor permeability (WVP), and water absorptivity were also affected by biopolymer coating, but the degree of change was dependent on the coating materials as well as treatment methods. For example, the rate of change in contact angle of water on paperboards decreased dramatically from 1.4 to 3.8 times depending on the coating materials as well as treatment methods. Generally, SPI-coated paperboards were more water-resistant than alginate coated ones. However, water resistance of the alginate-coated paperboards post-treated with the CaCl₂ solution was comparable to the SPI coated ones.     

大豆分离蛋白膜研究

以大豆分离蛋白(SPI)和甘油为成膜基质,研究多聚磷酸钠、羧甲基纤维素钠(CMC–Na)、微波及磷酸化对大豆分离蛋白膜性质影响。结果表明,多聚磷酸钠可显著提高膜的水溶性(ρ0.01)和抗拉伸强度(ρ0.05),显著降低膜的氧气透过性(ρ0.01)和水蒸气透过性(ρ0.05);CMC–Na能显著提高膜抗拉伸强度(ρ0.01)和氧气透过性(ρ0.05),显著降低膜的水溶性、透光率及水蒸气透过性(ρ0.01);微波处理可显著提高膜的抗拉伸强度(ρ0.05),降低膜的水溶性(ρ0.05);磷酸化可显著降低膜的氧气透过性(ρ0.05)、透光率及抗拉伸强度(ρ0.01)。     

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.     

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.     

The effect of fatty acid content on water vapour and carbon dioxide transmissions of cellulose-based edible films

Water vapour and CO₂ transmissions of methyl cellulose (MC)-based edible films with varying amounts of the fatty acids, stearic acid (SA), palmitic acid (PA) and lauric acid (LA) were studied and the results were compared with those obtained for a film without added fatty acid. Water vapour transmission rate (WVTR), water vapour permeance (WVPN) and water vapour permeability (WVP) values of films were determined by measuring the amounts of water vapour transmitted through the film and then adsorbed on anhydrous CaCl₂ as a function of time, using a static method. A recently-developed static method which utilises ascarite to adsorb carbon dioxide transmitted through the film was employed for the determination of carbon dioxide transmission rate (CO₂TR), carbon dioxide permeance (CO₂PN) and carbon dioxide permeability (CO₂P) of films. Among the three fatty acids studied, SA was found to be the most effective in decreasing both the water vapour and the CO₂ transmissions of films. In general, it was observed that WVTR, WVPN and WVP values of films decreased with increasing fatty acid content in the film composition. CO₂ transmission parameters also decreased with increasing SA and PA contents but increased with increasing LA content of films.     

Alginate-calcium films: Water vapor permeability and mechanical properties as affected by plasticizer and relative humidity

Alginate films containing dissimilar amounts of guluronate (G) and mannuronate (M): M/G∼0.45 and M/G∼1.5, soaked in a calcium chloride solution up to 20 min were evaluated for water vapor permeability (WVP). M/G∼0.45 films proved to be better moisture barriers at all calcium immersion times compared to M/G∼1.5. WVP of M/G∼0.45 and M/G∼1.5 films decreased as time of immersion in calcium increased; after 3 min, a decrease in WVP was observed. M/G∼0.45 films soaked for 1 min in calcium were further analyzed to determine the effect of plasticizer and relative humidity (RH) on their mechanical properties and WVP, using fructose, glycerol, sorbitol, and polyethylene glycol (PEG-8000). Films without plasticizer showed a lower capacity to adsorb water compared to those with plasticizer. As RH increased, tensile strength (TS) decreased and elongation (E) increased for all films. This effect was more pronounced on films containing plasticizer, which had lower TS at all RHs. Plasticizer did not increase E at 58% RH. At 78% and 98% RH, glycerol, sorbitol and fructose showed a significant increase in E compared to PEG-8000 and no-plasticizer. PEG-8000 provided lower TS and E, while glycerol showed the highest among all plasticizers. There was no difference on WVP between no-plasticizer and glycerol. Fructose and sorbitol showed the lowest WVP while PEG-8000 showed the highest.     

Mechanical and water vapor barrier properties of extruded and heat-pressed gelatin films

Gelatin-based edible films were produced by extruding hot melt of gelatin-based resins through a die with slot orifice and followed by heat-pressed method. The resins were plasticized with glycerol, sorbitol and the mixture of glycerol and sorbitol (MGS). The effect of type of plasticizer on extruded and heat-pressed (EHP) film-forming capacity was studied, and the mechanical and water barrier properties of resulting EHP gelatin films were compared with those of gelatin films prepared by solution casting method. Stretchable films were formed when glycerol or MGS were used as plasticizer, whereas resins plasticized with sorbitol were extruded in non-stretchable sheets. Glycerol plasticized gelatin film showed the highest flexibility and transparency among the EHP films tested. Tensile strength (TS), elongation (E) and water vapor permeability (WVP) of glycerol plasticized EHP gelatin films were 17.3 MPa, 215.9% and 2.46 ng m/m² s Pa, respectively, and EHP gelatin films had higher E values, lower TS values and higher WVP values compared to the glycerol plasticized cast gelatin films.     

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.     

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 partial hydrolysis and plasticizer content on the properties of film from cuttlefish (Sepia pharaonis) skin gelatin

Properties of film from cuttlefish (Sepia pharaonis) ventral skin gelatin with different degree of hydrolysis (DH: 0.40, 0.80 and 1.20%) added with glycerol as plasticizer at various levels (10, 15 and 20%, based on protein) were investigated. Films prepared from gelatin with all DH had the lower tensile strength (TS) and elongation at break (EAB) but higher water vapor permeability (WVP), compared with the control film (without hydrolysis) (p < 0.05). At the same glycerol content, both TS and EAB decreased, while WVP increased (p < 0.05) with increasing %DH. At the same DH, TS generally decreased as glycerol content increased (p < 0.05), however glycerol content had no effect on EAB when gelatins with 0.80 and 1.20% DH were used (p > 0.05). DH and glycerol content had no marked impact on color and the difference in color (ΔE^∗) of resulting films. Electrophoretic study revealed that degradation of gelatin and their corresponding films was more pronounced with increased %DH, resulting in the lower mechanical properties of films. Based on FTIR spectra, with the increasing %DH as well as glycerol content, higher amplitudes for amide-A and amide-B peaks were observed, compared with film from gelatin without hydrolysis (control film) due to the increased –NH₂ group caused by hydrolysis and the lower interaction of –NH₂ group in the presence of higher glycerol. Thermo-gravimetric analysis indicated that film prepared from gelatin with 1.20% DH exhibited the higher heat susceptibility and weight loss in the temperature range of 50–600 °C, compared with control film. Thus, both chain length of gelatin and glycerol content directly affected the properties of cuttlefish skin gelatin films.     

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.