Whey protein active films incorporated with a blend of essential oils: Characterization and effectiveness

Whey protein concentrate (WPC) films incorporated with a blend of Cinnamomum cassia, Cinnamomum zeylanicum, and Rosmarinus officinalis essential oils were characterized and evaluated for their effectiveness as an antioxidant for food applications. The effect of the incorporation of essential oils (EOs) at different concentrations (1, 2, 2.7, and 5% w/w) in WPC were studied by measuring their physical, optical, mechanical, and microstructural properties, in order to evaluate their behavior as a food packaging. The effectiveness of these active WPC films as a packaged was evaluated using a fatty food model (salami). The state of the salami oxidation was measured by the TBARs and hexanal assays during 180 days of storage. A yellowish characteristic color and opacity of WPC‐based films tend to increase with the increase of the EO concentration in the film formulation. While films containing 1 and 2% of EOs showed to be the most hydrophobic and present the lowest moisture content and solubility in water, films with higher EOs % (2, 2.7, and 5%, w/w) presented the highest water vapor transmission rate. The developed WPC active films showed to be heterogeneous, presenting cracks and pores due to the weakening of the polymer chain interaction forces by the EOs, which affected their mechanical behavior. WPC films incorporated with EOs may retard lipid oxidation induced by UV light in food. Besides, they showed to be very effective in the reduction of lipid oxidation in a previous assay with salami, with a longer storage time.     

Surface evaluation of whey protein films by atomic force microscopy and water vapour permeability analysis

The atomic force microscopy (AFM) technique is a powerful tool for studying surfaces and has been used to provide qualitative and quantitative information about nanometer‐scale matter properties that are often inaccessible by any other experimental technique. In this work AFM was used to evaluate the surfaces of edible films produced with whey protein concentrate (WPC). The morphology and the roughness of the films were analysed. The effects of WPC and plasticizer concentration were characterized in terms of water vapour permeability (WVP) and roughness parameters. Roughness was calculated through the images captured with AFM. AFM can be useful to identify structural changes of the film resulting from sample preparation. The results showed a relation between water vapour permeability and area roughness, through different sample preparation. The analyses of topography through roughness obtained with AFM, demonstrated the correlation between the morphology of the film, obtained with nanometer resolution and WVP. Copyright © 2004 John Wiley & Sons, Ltd.     

谷氨酰胺转氨酶改性蛋白类生物包装膜研究进展

谷氨酰胺转氨酶(TG)来源广泛,微生物、动物、植物体内都存在TG,其广泛应用于食品、纺织、医药、皮革等领域。综述了谷氨酰胺转氨酶对大豆分离蛋白膜、谷朊粉膜、花生分离蛋白膜、玉米蛋白膜等植物蛋白类生物包装膜和明胶膜、乳清蛋白膜等动物蛋白类生物包装膜性能的影响。蛋白类生物包装膜和其他材料的复合研究,将是未来可降解性膜的研究趋势之一。     

Grease Penetration and Browning Resistance of Pulpboard and Paperboard Coated with Whey Protein

Whey protein concentrate (WPC) was explored alone and in combination with sucrose (Suc) plasticizer as a grease‐barrier coating for bulrush pulpboard and solid bleached sulfate paperboard used in food packaging. WPC‐coated and WPC : Suc‐coated pulpboards showed better oil‐barrier properties compared with untreated, water‐treated or Suc‐coated pulpboards. Coating formulations with 10% WPC, without and with Suc, resulted in oil barriers comparable with commercial fluorinated hydrocarbon for pulpboard. When pulpboard trays containing cheesy pasta were microwave‐heated, 10% WPC : 20% Suc solution‐coated trays showed grease barrier property comparable with fluorinated hydrocarbon‐treated trays. Caramelization and Maillard browning of WPC and WPC : Suc coatings were initiated at 300°F, but microwave‐heated foods do not normally reach this high temperature. Paperboard with 10% WPC : 20% Suc solution coating had oil barrier comparable with polyethylene‐coated paperboards. WPC : Suc solution mixture at 2.5% : 5% and 3.3% : 7% were determined as the solution concentration minima for 4 and 24 h tests, respectively. HunterLab colorimeter L and b values indicated slight colour change of the paperboard coated with the higher WPC concentration solutions. Coating resulted in thicker paperboards but not in a linear manner. The 10% WPC : 20% Suc solution‐coated solid bleached sulfate paperboards on which slabs of butter sat in a refrigerator did not show any butterfat penetration, comparable with polyethylene‐coated paperboards and unlike uncoated paperboards that showed poor butterfat‐barrier properties. WPC : Suc coating was shown in this study to have potential to replace synthetic materials as a grease barrier. Copyright © 2011 John Wiley & Sons, Ltd.     

大豆分离蛋白与明胶蛋白复合膜的制备与性能研究

以大豆分离蛋白为基质,添加明胶蛋白,用溶液铸膜法制备复合膜.研究了成膜液的溶液性能;复合膜的各种性能,包括表观性能、力学性能、阻隔性能.通过扫描电子显微镜观察了膜的微观结构.结果表明,当明胶含量为30%(质量分数)左右,两种蛋白的相容性最佳,复合膜的各项性能达到较佳值,拉伸强度达到31.59MPa,断裂伸长率达到65.96%,并且对氧气和水都有良好的阻隔性.     

Characterization of antimicrobial films containing basil extracts

The properties of low‐density polyethylene (LDPE)‐based films containing either linalool or methylchavicol as antimicrobial (AM) additives were evaluated. Slight decreases in transparency, water vapour and oxygen transmission rates were found in the extruded films containing 0.34% w/w linalool or methylchavicol. The infrared (IR) spectra of the AM films were similar to that of additive‐free LDPE film. However, carbonyl peaks could also be observed in the spectra of the AM films. There was no significant difference in the degree of crystallinity and the melting temperature range of the different films. Derivative thermogravimetry mass‐loss curves showed that the thermal decomposition temperatures of the AM films were marginally lower than that of LDPE film. Electron micrographs indicated that AM LDPE‐based films exhibited no evidence of changes in microstructure to suggest that linalool and methylchavicol were not evenly distributed in the film. Copyright © 2006 John Wiley & Sons, Ltd.     

A Nanoporous Cytochrome c Film with Highly Ordered Porous Structure for Sensing of Toxic Vapors

Creating well‐ordered nanoporosity in biomolecules promises stability and activity, offering access to an even wider range of application possibilities. Here, the preparation of nanoporous protein films containing cytochrome c protein molecules is reported through a soft‐templating strategy using polystyrene (PS) spheres of different sizes as templates. The stability of the cytochrome c film is demonstrated through electrochemistry studies to show a reusable nature of these films over a long period of time. The size of the PS spheres is varied to tune the pore diameter and the thickness of the cytochrome c films, which are quite stable and highly selective for sensing toxic acidic vapors. The fusion of the templating strategy and the self‐assembly of biomolecules may offer various possibilities by generating a new series of porous biomolecules including enzymes with different molecular weights and diameters, peptides, antibodies, and DNA with interesting catalytic, adsorption, sensing, and electronic properties.     

Barrier and mechanical properties of methylcellulose–whey protein films

Water vapour permeability (WVP) and mechanical properties were assessed in edible films prepared from methylcellulose (MC) and MC–whey protein isolate (WPI) or MC–whey protein concentrate (WPC). Glycerol (Gly) was used as the plasticizer. Two MC–WP films were formulated. For Group I films, the mass ratio of WP : Gly was constant, whereas for Group II films the mass ratio of polymer (MC + WP) : Gly was constant. The WVP of MC–Gly film decreased with increasing MC concentration, while the tensile strength (TS) and percent elongation (E) increased. The WVP of Group I and Group II films decreased erratically and TS increased when the MC concentration was increased. Group I films had higher TS values than Group II films at the same MC : WP ratios. E of both groups increased with increasing MC concentration (p < 0.05), excluding the films with the highest MC : WP ratio tested (0.8) in Group I films. Group I films had lower E values than Group II films at the same MC : WP ratios. MC effectively governed WVP, TS and E of the WP films. Generally, MC–WP films of this work showed lower WVP than that of MC‐ and WP‐based edible films in the literature. This can potentially make MC–WP films a suitable film material for moisture‐sensitive food products. Copyright © 2005 John Wiley & Sons, Ltd.     

Comparison of flat film to total package water vapour transmission rates for several commercial food wraps

The barrier properties of a package are the sum of material and seal permeations. Although addressed for hermetically sealed and modified atmosphere packages, little consideration of total package permeation has been given to commercial food wraps. Standard protocols were used to compare the water vapour transmission rates (WVTRs) of materials and packages for seven commercial food wraps: aluminum foil; poly(vinylidene chloride) (PVdC) film; three poly(ethylene) (PE) films; an adhesive‐modified PE film; and plasticized poly(vinyl chloride) (PVC) film. Water ingress for a complete package was compared to calculated material permeation based on film WVTRs. Film‐to‐glass adhesion strength was also measured. Model systems (desiccant) were compared to foods at ambient and refrigeration temperatures. Aluminum foil had the lowest material WVTR (0.10 g/h/m²), closely followed by PVdC (0.13 g/h/m²). These WVTRs were approximately five‐fold lower than the PEs (～0.65 g/h/m²), which were nearly 10‐fold lower than PVC (4.9 g/h/m²). The adhesive‐modified PE film had the lowest difference between material and package transmission rates (0.7 E‐03 g/h), approximately half that of the PVdC film (1.1 E‐03 g/h), which was significantly lower than the remaining films (2.3 E‐03 –3.9 E‐03 g/h). The adhesive PE film had the strongest film–glass adhesion. Ambient food product test results were similar to model system (desiccant) results, but refrigerated trials showed significantly different relative package transmission rates. This was attributed to the reduced adhesion of most wraps at refrigeration temperatures. Copyright © 2002 John Wiley & Sons, Ltd.     

Evaluation of retail fresh meat packagings covered with stretch films of plasticized PVC and non‐PVC alternatives

The characteristics and performance of several non‐PVC stretch films were compared to those of plasticized PVC. Initially the main polymer components of the film were identified by infrared spectrometry and differential scanning calorimetry. The differences between films in mechanical properties, such as puncture resistance and tensile strength, varied about a factor of two, while the differences in elongation at break were considerably higher. Plasticized PVC showed properties somewhere in the middle. The water vapour transmission was highest for PVC, while its permeability to oxygen was the lowest. The potential for overall migration was assessed by substitute testing, using 95% ethanol and isooctane as test media, and the migration from PVC was found to be the highest. However, after use of the appropriate reduction factor of four, as allowed for fresh meat, the PVC film also proved to conform to legislation. The potential for specific migration was investigated by solvent extraction followed by gas chromatography. Twenty‐four components were identified, of which 11 could be compared to relevant migration limits based on evaluations of the EU Scientific Committee for Food. The release of solvents was estimated by direct thermal desorption at 100°C. Four films of different composition were used in a storage experiment with fresh beef. The meat quality was followed by measurements of colour, microbiological quality (total colony forming units and lactic acid bacteria) and lipid oxidation (thiobarbituric acid reactive substances) through a prolonged shelf‐life test. No differences in meat quality during normal shelf‐life were seen as a function of the film used. Copyright © 2004 John Wiley & Sons, Ltd.     

Effects of glycerol and sorbitol on optical,mechanical, and gas barrier properties of potato peel‐based films

Potato peel is a by‐product of potato‐based food production and seen as a zero‐ or negative‐value waste of which millions of tons are produced every year. Previous studies showed that potato peel is a potential material for film development when plasticized with 10% to 50% glycerol (w/w potato peel). To further investigate potato peel as a film‐forming material, potato peel‐based films containing the plasticizer sorbitol were prepared and investigated on their physicochemical properties in addition to films containing glycerol. Due to sufficient producibility and handling of casted films in preliminary trials, potato peel‐based films containing 50%, 60%, or 70% glycerol (w/w potato peel) and films containing 90%, 100%, or 110% sorbitol (w/w potato peel) were prepared in this study. Generally, with increasing plasticizer concentration, water vapor and oxygen permeability of the films increased. Films containing glycerol showed higher water vapor and oxygen permeabilities than films containing sorbitol. Young's modulus, tensile strength, and elongation at break decreased with increasing sorbitol concentration, whereas no significant effect of plasticizer content on elongation at break was shown in films containing glycerol. Due to crystallization of films containing sorbitol as a plasticizer, potato peel‐based films containing 50% glycerol (w/w) were identified as the most promising films, characterized by a water vapor transmission rate of 268 g 100 μm m^?2 d^?1 and an oxygen permeability of 4 cm³ 100 μm m^?2 d^?1 bar^?1. Therefore, potato peel‐based cast films in this study showed comparable tensile properties with those of potato starch‐based films, comparable water vapor barrier with those of whey protein‐based films, and comparable oxygen barrier with those of polyamide films.     

Evaluation of Antifungal Activity of Antimicrobial Agents on Cheddar Cheese

The antifungal activity against Aspergillus niger of the antimicrobial (AM) agents linalool, carvacrol and thymol incorporated in the coatings of starch‐based films was investigated. The activity was initially determined on a solid medium using the modified microatmosphere method and then examined on Cheddar cheese. On the solid media, all the AM films demonstrated a significant inhibitory effect against A. niger growth. The inhibitory effect of the AM films containing 2.38% (w/w) AM agents is reflected by the colony diameters that were 29.3, 25.4 and 21.3 mm for linalool, carvacrol and thymol, respectively, at 25°C after 7 days incubation compared with the control sample where the colony diameter was 85.3 mm. The AM films containing 2.38% (w/w) linalool, carvacrol or thymol reduced the population of A. niger on the surface of Cheddar cheese by 1.8, 2.0 and 2.2 log CFU/g, respectively, after 35 days of storage at 15°C. The results suggest that starch‐based film coated with an AM agent has the potential for being used as a fungicidal packaging system. Copyright © 2012 John Wiley & Sons, Ltd.     

High Dielectric Performances of Flexible and Transparent Cellulose Hybrid Films Controlled by Multidimensional Metal Nanostructures

Various wearable electronic devices have been developed for extensive outdoor activities. The key metrics for these wearable devices are high touch sensitivity and good mechanical and thermal stability of the flexible touchscreen panels (TSPs). Their dielectric constants (k) are important for high touch sensitivities. Thus, studies on flexible and transparent cover layers that have high k with outstanding mechanical and thermal reliabilities are essential. Herein, an unconventional approach for forming flexible and transparent cellulose nanofiber (CNF) films is reported. These films are used to embed ultralong metal nanofibers that serve as nanofillers to increase k significantly (above 9.2 with high transmittance of 90%). Also, by controlling the dimensions and aspect ratios of these fillers, the effects of their nanostructures and contents on the optical and dielectric properties of the films have been studied. The length of the nanofibers can be controlled using a stretching method to break the highly aligned, ultralong nanofibers. These nanofiber‐embedded, high‐k films are mechanically and thermally stable, and they have better Young's modulus and tensile strength with lower thermal expansion than commercial transparent plastics. The demonstration of highly sensitive TSPs using high‐k CNF film for smartphones suggests that this film has significant potential for next‐generation, portable electronic devices.     

Influence of co‐monomer structure on properties of co‐polyamide packaging films

In this work a series of co‐polyamides were prepared by random polymerization of ?‐caprolactam in presence of four different co‐monomers at a percentage of 5% w/w, with the aim of verifying their suitability as film‐forming materials. The effects of structural changes induced in the ?‐caprolactam homopolymer by co‐monomers were evaluated in both molten and solid states. Rheological tests in shear and elongational flow were performed to evaluate the processability of co‐polyamides. Cast films were obtained and their thermal, mechanical and transport properties were evaluated to establish the performances of the co‐polyamides in view of packaging applications. The results indicate that co‐polyamide films having a partially aromatic structure display the best mechanical performances and show a significant improvement in barrier properties to gases compared to the homopolymer. Copyright © 2002 John Wiley & Sons, Ltd.     

Molecular beam epitaxial growth of high-Tc Bi-Sr-Ca-Cu-O Films

Molecular beam epitaxy (MBE) has been used to grow high-temperature superconducting Bi-Sr-Ca-Cu-O films with adequate control over growth of number of unit layers. Oxide sources of Sr and Ca used for electron beam evaporation have been found to be useful for epitaxial growth of films. Deposited films show superconducting properties comparable to films deposited by using pure metals with a complicatedin situ oxidation technique. Optimum deposition and annealing conditions have been obtained to growc-axis-oriented 2212 phase BSCCO film.In situ reflection high-energy electron diffraction (RHEED) study of the films has revealed the growth of epitaxial films with atomically smooth surfaces.     

The properties of gelatin film‐neem extract and its effectiveness for preserving minced beef

The properties of gelatin films developed from neem extract (NE; Azadirachta indica) were determined. Moreover, the developed films were applied to minced beef to test its effectiveness for preserving the meat. The quality attributes of the minced beef wrapped with the developed film were monitored over a 7‐day period in refrigerated storage (4 ± 1°C) and were compared to a control commercial wrap film (polyvinyl chloride). The addition of NE improved the elongation at break, solubility, and antioxidant activity of the gelatin films. After 7 days of storage, the minced beef wrapped with the experimental film showed the highest a* and weight loss values. Gradually, changes in TBARS were more pronounced in the experimental sample. It was concluded that gelatin film containing NE is a potentially promising film that could help delay oxidative reactions. However, some characteristics of the film (eg, mechanical properties and water vapor permeability) need to be improved before putting them to commercial use.     

Ultraflexible Transparent Bio‐Based Polymer Conductive Films Based on Ag Nanowires

The unstable mechanical properties of flexible transparent conductive films (TCFs) make it difficult for them to meet the requirements for displays or wearable devices. Here, the relationship between the mechanism behind the bending behavior and the electrical properties, which is important for improving the mechanical stability of flexible TCFs, is explored. Flexible TCFs are reported based on silver nanowires (AgNWs) and bio‐based poly(ethylene‐co‐1,4‐cyclohexanedimethylene 2,5‐furandicarboxylate)s (PECFs), with a low sheet resistance (23.8 Ω sq^?1 at 84.6% transmittance) and superior mechanical properties. The electrical properties of the AgNW/PECFs composite film show almost no change after bending for 2000 times.     

Evaluation of a bio‐coating as a solution to improve barrier,friction and optical properties of plastic films

The present research dealt with evaluating barrier, friction and optical properties of three different plastic films after deposition of a gelatin‐based bio‐coating. The composite films showed improved barrier properties against oxygen and UV radiation. The oxygen transmission rate decreased in the order of 73% for oriented polypropylene (OPP), 56% for low‐density polyethylene (LDPE) and 40% for polyethylene terephthalate (PET). The increased UV barrier characteristics ranged from 20% for OPP to 12% for both LDPE and PET. Static and kinetic coefficients of friction significantly decreased both in the film‐to‐film and in the film‐to‐metal tests, leading to a desirable value for many applications. However, bio‐coated films showed lower optical performances in terms of transparency and haze. Transparency decreased mainly for LDPE (36%), whereas the haze index increased especially for OPP (85%). Non‐significant differences were observed as far as the water vapour permeability was concerned, except for a slight reduction for PET (from 15.78 to 13.53 cm³/m²/day at 23°C and 90% of relative humidity), suggesting that non‐meaningful effects arose from the addition of a hydrophobic component in the original formulation. Finally, the solubility of the coating in water was around 25% for all the three plastic substrates. The obtained data suggest that the lipid protein coating tested in this study, in spite of its great potential for enhancing some characteristics of plastic packaging films, still exhibits negative aspects which necessitate further improvement. Copyright © 2008 John Wiley & Sons, Ltd.     

Mineral Oil Barrier Testing of Cellulose‐Based and Polypropylene‐Based Films

Recycled cardboard has been identified as a major source of mineral oil hydrocarbon (MOH) contamination of foods. Identifying and using appropriate functional barriers is a mechanism through which this problem can be addressed. A number of cellulose‐based and biaxially oriented polypropylene (BOPP) films were evaluated as potential functional MOH barriers. The films were tested using a donor material, a paper containing MOH placed on one side of the film barrier and a paper which acted as the receptor on the other. Testing was performed at accelerated conditions of 60°C, the receptor analysed periodically for MOH. The results demonstrated that the cellulose‐based film types provided an MOH barrier of >3.5 years. This contrasted with the BOPP selected films, for which only the proprietary acrylic‐coated BOPP film provided an effective barrier to MOH migration. Further investigation of the MOH barrier properties of the proprietary acrylic‐coated BOPP film was undertaken. Various coating strategies were employed including increasing the coating application weight, increasing the number of coating lay downs and coating one or both surfaces of the film. It was found that an MOH barrier of 1.5 years when tested at 40°C could be achieved for the proprietary acrylic‐coated BOPP film; however, barrier effectiveness was dependent on the coating integrity of the film. Further work with a vertical form filler packaging machine and the use of a staining technique with transmission microscopy proved effective at highlighting and assessing the coating integrity of packets during a typical packaging operation. Copyright © 2014 John Wiley & Sons, Ltd.     

Fabrication and Properties of Antioxidant Polyethylene‐based Films Containing Marigold (Tagetes erecta) Extract and Application on Soybean Oil Stability

Four films were extruded in a pilot‐plant scale blown extrusion machine: a monolayer low‐density polyethylene (LDPE) film added with 2.90% of marigold (Tagetes erecta) extract, a two‐layer high‐density polyethylene/LDPE film added with 3.59% of the extract in the LDPE layer and the corresponding two control films without addition of the extract. More than 64% of astaxanthin contained in the extract was lost during the extrusion process. Spectroscopic, optical and mechanical properties of the films were affected by the addition of the marigold extract. The films showed to be light sensitive when exposed to commercial light at 25 °C; however, bags made of the films showed a positive effect on soybean oil stability when used as packaging. Copyright © 2012 John Wiley & Sons, Ltd.