Effect of clay content, homogenization RPM, pH, and ultrasonication on mechanical and barrier properties of fish gelatin/montmorillonite nanocomposite films

The effect of clay content, homogenization RPM, and pH on the mechanical and barrier properties of fish gelatin/nanoclay composite films was investigated. The addition of 5% nanoclay (w/w) increased the tensile strength from 30.31 ± 2.37 MPa to 40.71 ± 3.30 MPa. The 9 g clay/100 g gelatin film exhibited the largest improvements in oxygen and water barrier properties. Oxygen permeability decreased from 402.8 × 10⁻⁶ ± 0.7 × 10⁻⁶ g m/m² day atm to 114.4 × 10⁻⁶ ± 16.2 × 10⁻⁶ g m/m² day atm and the water vapor permeability decreased from 31.2 × 10⁻³ ± 1.6 × 10⁻³ ng m/m² s Pa to 8.1 × 10⁻³ ± 0.1 × 10⁻³ ng m/m² s Pa. The XRD and TEM observation suggested that the ultrasonication treatment (30 min at 40% output) resulted in exfoliation of the silicates.     

Film and pharmaceutical hard capsule formation properties of mungbean,waterchestnut, and sweet potato starches

Biodegradable films were developed using mungbean, waterchestnut and sweet potato starches as base raw materials. The physical and mechanical properties of the films were compared with gelatin and HPMC films. The same starches were used to develop hard capsules for utilization in the pharmaceutical industry as a substitute for gelatin or animal based products. Starches with high amylose content had excellent film and hard capsule forming abilities and properties compared to the starches with low amylase content. The starch films also had excellent oxygen barrier properties (0.048 ± 0.008 to 0.070 ± 0.009 fl m/m² s Pa), but water barrier properties (1.1 ± 0.5 to 1.8 ± 0.4 ng m/m² s Pa) were higher than LDPE (0.00064 ng m/m² s Pa) synthetic polymer films. The tensile strength values of starch films (12.1 ± 0.7 to 19.0 ± 2.2 MPa) were not significantly different from gelatin (19.5 ± 1.6 MPa) and HPMC (19.9 ± 1.2 MPa) films. In the case of elongation properties, starch films had lower values (42.2 ± 7.7 to 79.4 ± 9.2%) than gelatin film (122.0 ± 14.6%), but higher than HPMC film (13.8 ± 4.2%). Molecular (SEC-MALLS) and physical (viscosity) characterization of vegetable starches, indicated that the starches with high amylose content produced better biopolymer films and capsules compared to the starches with low amylose and high amylopectin content. Biodegradable films and hard capsules for pharmaceutical applications could be developed from vegetable starches with similar physical and mechanical properties as synthetic and gelatin products.     

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.     

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.     

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.     

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.     

Development and Characterization of Soy Protein Isolate Emulsion-Based Edible Films with Added Coconut Oil for Olive Oil Packaging: Barrier,Mechanical, and Thermal Properties

Emulsion-based edible films made of soy protein isolate (SPI), virgin coconut oil (VCO), and soy lecithin (SL) and plasticized with glycerol were prepared using the casting method. The effect of VCO and SL concentrations in SPI films and their in-between interaction were studied through the evaluation of physical (moisture and opacity), mechanical (elongation and tensile strength), water vapor permeability, and thermal properties. The response surface methodology was used to identify the most significant factors in the properties studied. The applicability of SPI emulsion-based films was evaluated as a package for olive oil to be used in small portions. The oxidative stability of the packaged olive oil was monitored by peroxide analyses during 28 days. The incorporation of VCO and SL decreased the moisture content and increased the elongation of the SPI emulsion-based films when compared to the SPI film without these components (control). The opacity of the films increased with the addition of VCO into the protein-based films, but not with the addition of SL or a combination of both constituents. By the other hand, the water vapor permeability was not improved by the incorporation of VCO, SL, or a combination of both. The peroxide value of the olive oil stored in SPI emulsion-based film sachets increased rapidly during the seven first days of storage. After this period, the peroxides increased relatively slow up to 28 days of storage. The peroxide values of the packaged olive oil did not reach the maximum limit recommended by the Codex Alimentarius. Based on these results, this work may be useful for the technological enhancement of emulsion-based films or for food packaging applications.     

Effect of the ripening time under vacuum and packaging film permeability on processing and quality characteristics of low-fat fermented sausages

The effect of vacuum ripening of low-fat fermented sausages packaged in films with different permeabilities on their microbiological, physicochemical and sensorial characteristics was studied. High-fat control sausages were produced with 30% initial fat and low-fat sausages with 10% initial fat. The low-fat sausages were separated into: (a) non-packaged (control) and (b) packaged under vacuum on 7th, 12th and 17th day of processing, remaining under vacuum during the ripening period for 21, 16 and 11 days, respectively, in three different oxygen (100, 38 and ? 5 cm³/m²/24 h/1 atm) and water vapour (4.5, <2.5 and 1 g/m² 24 h) permeability plastic bags. Vacuum packaging reduced (p < 0.05) the weight loss, the hardness and extent of lipid oxidation in the sausages, increased (p < 0.05) their lightness, but had no effect (p > 0.05) on the redness, compared to the control sausages. Packaging low-fat fermented sausages under vacuum for the last 11 days of ripening in packaging film with high permeability increased (p < 0.05) the lactic acid bacteria count. The same product packaged in film with medium permeability had a higher (p < 0.05) Micrococcaceae count and the same (p > 0.05) hardness and overall acceptability as the high-fat control sausages. A ripening time of 11 days and the medium packaging film permeability were the most appropriate conditions for the vacuum packaging of low-fat fermented sausages.     

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.     

Preparation and Characterization of an Olive Flounder (Paralichthys olivaceus) Skin Gelatin and Polylactic Acid Bilayer Film

Olive flounder skin gelatin (OSG) was used as a film base material. A bilayer film of OSG and polylactic acid (PLA) was prepared using solvent casting method to enhance the film properties. Physical properties of the OSG–PLA film were increased compared with the nonaugmented OSG film. In particular, the PLA lamination decreased water vapor permeability from 2.17 to 0.92 × 10^?9 g·m/m²·s·Pa, as well as of the water solubility from 16.62% to 9.27%, in the bilayer film relative to the OSG film. The oxygen permeability of the OSG–PLA bilayer film was held low by the OSG film, compensating for the high oxygen permeability of the PLA layer. Therefore, the OSG–PLA bilayer film with its enhanced physical properties and high water and oxygen barrier properties can be applied as a food packaging material.     

Mechanical properties and water vapor permeability of edible films made from fractionated soy proteins with ultrafiltration

Soy protein isolates (SPI) were fractionated by ultrafiltration unit equipped with 100 and 300 kDa cutoff size membranes. Glycerol-plasticized fractionated soy protein films were developed by casting methods. Mechanical, moisture barrier and physical properties of films, as affected by molecular weight of soy protein fraction, were investigated. Tensile strength and percent elongation at break of films increased with molecular weight of soy proteins. However, molecular weight variation did not influence the water vapor barrier properties of films. Protein solubilities of fractionated films were in the range of 3.5-4.6 g/100 g of dry film, whereas 11.9 g of proteins were solubilized from 100 g of dry SPI film. Hunter b value of fractionated protein films decreased with molecular weight of soy protein.     

Physical assessment of composite biodegradable films manufactured using whey protein isolate,gelatin and sodium alginate

Composite films were manufactured using whey protein isolate (WPI), gelatin (G) and sodium alginate (SA) using a simplex centroid design. Tensile strength (TS), puncture strength (PT), percentage elongation at break point (E), tear strength (TT), water vapour permeability (WVP) and oxygen permeability (OP) of films were evaluated. The interactions between biopolymers showed quadratic effects (P < 0.01) on TS, E, PT, TT and WVP values. Scanning electron microscopy (SEM) was performed to investigate the microstructures of composite films. The proportion of ingredients required to produce the optimum composite films was determined to be: WPI (g):G (g):SA (g) = 8.0:12.0:5.0. Overall, films (WPIGSA-9) produced using the combination of WPI (g):G (g):SA (g) = 10.0:16.0:14.0 demonstrated the best barrier to oxygen (8.00 cm³ μm/m² d kPa); while films (WPIGSA-1) showed the best barrier to water vapour (48.04 g mm/kPa d m²); films (WPIGSA-6) using the combination of WPI (g):G (g):SA (g) = 10.0:17.5:22.5 had the best mechanical properties of all of the experimental composite films tested.     

Study of the retention and release of n-hexanal incorporated into soy protein isolate–lipid composite films

This work deals with the study of the kinetic of aroma release, which had been previously incorporated into soy protein isolate (SPI)–lipid composite films. The aim was to determine the influence of type and amount of lipidic material on aroma (n-hexanal) release and retention, as well as the apparent diffusion coefficients. To carry out this study it have been employed SPI-based films containing two SPI:LIPID ratios (1:0.25 and 1:0.5), and two types of lipids, oleic acid (OA) and beeswax (BW), in OA:BW ratios 100:0, 70:30, 50:50, 30:70 and 0:100. The measurements were performed by a gas chromatography technique. The films that showed more retention were SPI:LIPID 1:0.5 100% BW and control film. Concerning release rate, films containing BW as unique lipid material gave the lowest aroma release rate. Apparent diffusion coefficients (D_app) of all films are in the same order of magnitude (10⁻¹⁵ m² s⁻¹). D_app decreases when BW increases in the film matrix and when oleic acid amount decreases. In conclusion, for encapsulating n-hexanal, SPI-BW films demonstrated the best performances, followed by control film (without lipids).     

Effect of chemical and physical pretreatments on the convective drying of cape gooseberry fruits (Physalis peruviana)

Drying of cape gooseberry fruits is a slow process because of the low permeability to moisture of the fruit’s waxy skin. In this work, the effect of chemical pretreatments (sunflower oil/K₂CO₃ or olive oil/K₂CO₃ at 28 °C, and NaOH/olive oil at 96 °C) and physical pretreatments (blanching) to break down the waxy surface and accelerate moisture diffusion during drying, was assessed. Drying was carried out at 60 °C and 2 m/s air velocity for 10 h. The lowest moisture content (0.27 kg water/kg db), the highest vitamin C content (0.36 mg/g), and the greatest rehydration capacity (1.89) were obtained in fruits pretreated with olive oil (9.48%) and K₂CO₃ (4.74%). However, the greatest changes in color (ΔE^* = 15.05) and chroma (ΔC^* = 9.03) were also associated to fruits pretreated with olive oil and K₂CO₃. The effective diffusivity of water during drying was 7.37 × 10⁻¹¹ m²/s in pretreated samples compared with 6.61×10⁻¹¹ m²/s for untreated samples.     

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.     

Preparation and properties of dialdehyde carboxymethyl cellulose crosslinked gelatin edible films

Glycerol-plasticized gelatin edible films with a new kind of dialdehyde polysaccharide, dialdehyde carboxymethyl cellulose (DCMC) as crosslinking agent are successful prepared using casting techniques. The mechanical properties, thermal stability, light barrier properties, swelling behavior as well as water vapor permeability (WVP) of the gelatin-DCMC films are investigated. The results indicate that the addition of DCMC causes tensile strength (TS) and thermal stability to increase and elongation at break (EB) to decrease, suggesting the occurrence of crosslinking between gelatin and DCMC. The light barrier measurements present high values of transparency at 280 nm and low values of transparency at 600 nm of the gelatin-DCMC films, indicating that gelatin-DCMC films are very transparent (lower in transparency value) while they have excellent barrier properties against UV light. Moreover, the values of transparency at 280 nm increase with the increased DCMC and glycerol content, suggesting the potential preventive effect of gelatin-DCMC films on the retardation of product oxidation induced by UV light. Furthermore, the addition of DCMC can greatly decrease the water vapor permeability (WVP) and equilibrium swelling ratio (ESR) down to values about 1.5 × 10⁻¹⁰ g m/m² s Pa and 150%, revealing the potential of DCMC in reducing the water sensitivity of gelatin-based films. In common for hygroscopic plasticizer in edible films, the addition of glycerol gives increase of EB and WVP and decrease of thermal stabilities and ESR of the gelatin-DCMC films.     

Physico-chemical properties,morphology and antioxidant activity of film from fish skin gelatin incorporated with root essential oils

The influences of three root essential oils (ginger, turmeric and plai) at different levels (25%, 50% and 100%, based on protein content) on properties and antioxidative activity of fish skin gelatin-based film were investigated. Films incorporated with all essential oils showed the lower tensile strength (TS) but higher elongation at break (EAB) with increasing amount of essential oils, compared with the control film (without oil incorporated), regardless of types of essential oil (p < 0.05). Water vapor permeability (WVP) of films containing essential oils decreased as the amount of essential oils increased (p < 0.05). Decreases in L^*-value and increases in b^*-, ΔE^*- and transparency value were observed with increasing amount of essential oils incorporated (p < 0.05). FTIR spectra indicated that films added with essential oils, especially from plai root, exhibited higher hydrophobicity than the control film, as evidenced by higher amplitude at wavenunber of 2877–2922 cm⁻¹ and 1732 cm⁻¹. Lower degradation temperature was obtained in films containing essential oils. Microstructural study revealed that bilayer films could be formed when essential oils at level above 50% were incorporated. Film incorporated with plai and turmeric essential oils showed the higher DPPH and ABTS radical scavenging activity, respectively, (p < 0.05), compared with the control film and ginger essential oil added film. Thus, the incorporation of root essential oils directly affected properties of fish skin gelatin-based film, depending on types and levels incorporated.     

Rinse Treatment and Oxygen Barrier Properties of Films for Improving Quality Retention in Vacuum-Skin Packaged Fresh Chicken

Fresh chicken drumsticks rinsed with water or salt solution (28% NaCl) were vacuum‐skin packaged in films differing in oxygen transmission rate (OTR) (< 10, 3000, ≥ 7000 cm³/m²/24 h). Salt rinsing decreased surface lightness (CIE L*). Higher OTR films maintained surface redness (CIE a*) better than oxygen barrier film. Neither rinse nor film OTR had any effect on yellowness (CIE b*). Salt rinsing drumsticks also reduced drip loss. Counts of aerobic and coliform bacteria increased during storage for product in all films. Within each film, salt‐rinsed drumsticks had lower counts at 3 and 6 d of storage (through 12 d) for total aerobic and coliform bacteria, respectively. Product in low OTR (barrier) film generally had lower bacteria counts than product in higher OTR films.     

Structure-modifying alkaline and acidic pH-shifting processes promote film formation of soy proteins

The effect of pH-shifting, a process that induces the molten globule state in proteins, on the film-forming potential of soy protein isolate (SPI) at different temperatures was investigated. Partial unfolding at pH 1.5 or 12, followed by refolding at pH 7.0, was performed to alter the protein structure. Glycerin-plasticised films were prepared from pH-treated SPI at ambient temperature (20 °C), or by heating at 50, 60, 70, or 80 °C (30 min). Tensile strength (TS), elongation at break (EAB), water vapour permeability (WVP), protein solubility (pH 3–7), and non-participating proteins of films were analysed, and the film microstructures were examined. The pH₁₂-treated SPI spontaneously formed a transparent, slightly yellowish film at 20 °C, which had the greatest EAB, while pH_1.5-treated and native SPIs required preheating at 50 and 70 °C, respectively, to form a film. Heating generally decreased solubility and WVP but increased TS. Films formed from both pH₁₂- and pH_1.5-treated SPIs were more elastic (up to 2-fold greater in EAB, P < 0.05) than the film formed from untreated SPI despite slightly reduced TS and WVP. Electrophoresis revealed disulphide bonds between A and B subunits of glycinin being a dominant force in pH₁₂- and pH_1.5-treated SPI films, while noncovalent forces were abundant in untreated SPI films. The pH₁₂-treated SPI film consisted of more interactive protein strands than other SPI films, which seemed to explain its superior elastic properties.     

Biodegradable three-layer film derived from bovine gelatin

Biodegradable three-layer gelatin film was obtained by heat – compression of piled dialdehyde starch (DAS) – cross-linked and plasticized-gelatin films (Ge-10DAS) outer layers and sodium montmorillonite (MMt) – plasticized – gelatin film (Ge-5MMt) inner layer. Multilayer film displayed a compact and uniform microstructure due to the highly compatible individual layers which could interact by strong hydrogen bonding. Lamination reduced moisture absorption and total soluble matter compared to the single layers while keeping transparency. Tensile strength and elastic modulus of the multilayer were 8.0 ± 1.3 MPa and 14.7 ± 2.4 MPa, which were significantly higher than values obtained for Ge-10DAS due to the contribution of the of the bio-nanocomposite inner layer. Elongation at break was not affected by lamination meanwhile it had a beneficial effect on barrier properties. Water vapor permeability (WVP) of the multilayer was 0.8 ± 0.1 × 10⁻¹³ kg m Pa⁻¹ s⁻¹ m⁻² which was lower than those of the individual components whereas oxygen permeability was similar to that of Ge-5MMt (10.5 ± 0.4 cm³(O₂) mm m⁻² day⁻¹) and lower than that of Ge-10DAS film.