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.     

Development and characterization of PET/Fish Gelatin–nanoclay composite/LDPE laminate

A three‐layer laminate film was developed with the following structure: polyethylene terephthalate (PET)/fish gelatin (FG)–nanoclay composite/low‐density polyethylene (LDPE). The FG–nanoclay composite material functioned as the oxygen barrier layer and demonstrated comparable oxygen barrier properties when compared with a similar laminate utilizing ethylene vinyl alcohol as the barrier layer at a relative humidity (RH) of up to 50%. The introduction of nanometer‐sized filler clay into the FG matrix lowered the oxygen permeability (OP) because of the tortuosity effect of the clay particles. In addition, the FG–nanoclay composite film exhibited bond strengths similar to both LDPE and PET. The hydrophilic nature of FG significantly increases OP under high (>50%) RH conditions. However, this new FG laminate film could be a possible alternative for packaging designers desiring a more sustainable packaging material for low‐RH (<50%) applications. Copyright © 2009 John Wiley & Sons, Ltd.     

Technofunctional Properties of Films Made From Ethylene Vinyl Acetate/Whey Protein Isolate Compounds

One challenge faced by the plastics industry is that crude oil will become scarcer and more expensive in the future. Furthermore, an increase in plastic waste is leading to a strongly growing demand for sustainable alternatives to traditional, crude oil‐based polymers in the packaging sector. The aim of this study was to investigate the influence of the incorporation of whey protein isolates (WPIs) on the technofunctional properties of ethylene vinyl acetate (EVA) films. The compounding EVA with WPI was conducted in a co‐rotating twin‐screw extruder at varying processing temperatures. WPI and hydrolysed WPI with a degree of hydrolysis of 10% were used up to 35% (w/w) as filler. The tensile strength and elongation at break of the resulting EVA‐based films decreased significantly with increasing filler content. Because of the hydrophilicity of WPI, the water vapour permeability of the films increased. Advantageously, the oxygen barrier was enhanced by 50–80% compared with that of pure EVA films, which offered the potential of using whey proteins as a filler in compounds for packaging materials for their oxygen barrier properties. In addition, this study provides a promising perspective on the thermoplastic processing of whey protein formulations in the future. Copyright © 2013 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.     

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.     

Effects on Oxygen‐barrier Properties of Pretreating Paperboard with a Starch–Poly(Vinyl Alcohol) Blend before Polyethylene Extrusion

Polyethylene (PE) extrusion coating was performed on paperboard pre‐coated with water‐borne barrier coatings based on starch–poly(vinyl) (PVOH)–plasticizer blends in order to investigate that how the addition of a plasticizer to the pre‐coating affects the oxygen‐barrier properties of the board after PE extrusion coating. The plasticizers used were glycerol, polyethylene glycol (PEG) and citric acid (CA). Photomicrographs showed that the barrier coating layers were rather smooth, but defects were observed in the starch–PVOH layers when a plasticizer was added. Starch–PVOH layers had oxygen‐barrier properties similar to those of pure PVOH without plasticizers. When a sufficient number of layers (four layers) were applied to cover defects, the starch–PVOH layers containing CA showed oxygen transmission rate (OTR) values similar to those of starch–PVOH layers without plasticizer. The adhesion of PE to pre‐coated paperboard decreased when a plasticizer was added to the pre‐coating recipes. PE extrusion coating resulted in a reduction in the OTR in the case of pre‐coating formulations containing plasticizers. A lower OTR after polyethylene extrusion was observed with PEG as plasticizer than with CA as plasticizer. This could be explained by the increase in brittleness due to cross‐linking under the high temperature load during the extrusion process. Dynamic mechanical analysis of the films showed a substantial increase in storage modulus between 100°C and 200°C for CA‐containing starch–PVOH films. The contact angle of diiodomethane on the pre‐coating layer decreased when a plasticizer was added to the coating recipe indicating an increase in wetting of the PE melt. Addition of PEG to the pre‐coating led to a greater wetting than the addition of CA, and this may have sealed some defects in the pre‐coating leading to lower OTR values.     

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.     

乳清蛋白添加量对交联羧甲基玉米淀粉可食膜阻隔性能的影响

以交联羧甲基玉米淀粉(CCMS)为原料,辅以增强剂、增塑剂、脱泡剂及脱膜剂等,通过流延方法制备了交联羧甲基玉米淀粉/乳清蛋白可食性复合包装膜。实验考察了乳清蛋白粉的添加量对交联羧甲基玉米淀粉可食性膜阻隔性能的影响。结果表明:乳清蛋白添加量为15%(质量分数)时,可食性复合膜的阻隔性最好,其透氧系数为0.312×10-15cm3.cm/(m2.s.Pa),水蒸气透过系数为2.89 g.mm/(m2.d.kPa),吸水稳定性好。     

Packaging‐related properties of protein‐ and chitosan‐coated paper

The mechanical and gas‐barrier properties of paper and paperboard coated with chitosan–acetic acid salt (chitosan), whey protein isolate, whey protein concentrate and wheat gluten protein were studied. Paper sheets were solution‐coated using a hand applicator. In addition, bi‐layer composites of wheat gluten and paper or paperboard were produced by compression moulding, and the chitosan solution was also applied on paperboard using curtain coating. Young's modulus, fracture stress, fracture strain, tearing strength, air permeance and oxygen permeability were assessed. The mechanical and air permeance measurements of solution‐coated paper showed that chitosan was the most effective coating on a coat weight basis. This was due to its high viscosity, which limited the degree of penetration into the paper. The proteins, however, also enhanced the strength and toughness of the paper. Compression‐moulded wheat gluten/paper or paperboard, as well as curtain‐coated chitosan paperboard laminates, showed oxygen barrier properties comparable to those of paper and paperboard coated with commercial barrier materials. None of the composites could be delaminated without fibre rupture, indicating good adhesion between the coatings and the substrates. Copyright © 2005 John Wiley & Sons, Ltd.     

Properties of polysaccharide‐coated polypropylene films as affected by biopolymer and plasticizer types

Plasticized polysaccharide coatings on polypropylene (PP) film were prepared to evaluate the optical and tensile properties of the resulting coated films, as affected by biopolymer and plasticizer types, in order to develop a novel film structure of biopolymer coatings on common plastics intended for food packaging applications. Composite structures of PP film coated with several kinds of polysaccharides (MC, HPMC, chitosan, κ ‐carrageenan, dextrin) and plasticizers (PG, glycerol, PEG, sucrose, sorbitol) were obtained through a simple casting method. High glossy surfaces were observed on the coated films with chitosan and κ ‐carrageenan, with the sucrose‐plasticized chitosan coating giving the highest gloss of 142.7 GU. Biopolymers, but no plasticizers, exerted noticeable influence on the colour of the coated films. Chitosan‐ and κ ‐carrageenan‐coated PP films also showed greater transparency, tensile strength and elongation than the other coated films. Nisin‐incorporated κ ‐carrageenan coatings on PP film exhibited significant bacterial growth inhibition against Lactobacillus plantarum . The results suggest that coatings based on chitosan and κ ‐carrageenan with proper plasticizers possess excellent visual and mechanical characteristics and have great potential for acting efficiently as antimicrobial agent carriers in active packaging systems. Copyright © 2004 John Wiley & Sons, Ltd.     

Development of multilayer films with improved aroma barrier properties for durian packaging application

The symmetrical A/B/A structure of multilayer blown films was fabricated in this study. The immiscible low‐density polyethylene/polylactic acid (LDPE/PLA) blend was set as a core (B) layer and LDPE was used as skin (A) layers. The compositions of PLA in the core layer were varied from 20 to 50 wt%. The thickness of each layer was 10 μm (total film thickness of ~ 30 μm). In a blown film co‐extrusion process, the morphology of the fiber/ribbon‐like structures of LDPE/PLA blend was developed. Such structures had interesting effects on gas permeability and aroma barrier properties of the films. For instance, multilayer LDPE films containing 40 and 50 wt% PLA (P40 and P50) showed the reduction of oxygen permeability (PO₂) approximately 20% and 43%, respectively, compared with the neat LDPE film. A long tortuous path for gas and aroma transportation through film thickness was created from the developed ribbon‐like structures of the PLA minor phase. For durian packaging application, fresh‐cut durian of 300 g was packed in the developed multilayer films, LDPE, and HDPE (Control), stored at 4°C for 7 days. Results demonstrated that the steady‐state condition of 10% to 13% O₂ and 8% to 10% CO₂ was achieved in all packages except in the HDPE. Moreover, the P40 and P50 films exhibited an outstanding aroma barrier property for three major durian volatiles : diethyl sulfide, ethyl propanoate, and 2‐ethyl‐1‐hexanol. Overall results clearly indicated that the multilayer LDPE films containing PLA exhibited a significantly improved aroma barrier performance with optimum gas permeability desirable for modified atmosphere packaging to retain quality of fresh‐cut durian throughout the storage period.     

Effect of UV‐Radiation on the Packaging‐Related Properties of Whey Protein Isolate Based Films and Coatings

The high oxygen barrier properties of whey protein based films and coatings means these materials are of great interest to the food and packaging industry. However, these materials have poor mechanical properties such as the tensile strength, Young's modulus and elongation at break. Up until now, the influence of ultraviolet (UV) radiation on whey protein films has not been reported in the literature. This study thus investigates the influence of UV‐radiation on the properties of whey protein based films. UV‐irradiated films showed increased tensile strength and a yellowing that was dependent on the radiation time. After irradiation, the films showed no significant change in the barrier properties, Young's modulus or elongation at break. In addition, a protein solubility study was undertaken to characterize and quantify changes in structure‐property relationships. The significant decrease in protein solubility in buffer systems which break disulfide and non‐covalent bonds indicates that additional molecular interactions arise with increasing radiation dose. This study provides new data for researchers and material developers to tailor the characteristics of whey protein based films according to their intended application and processing. Copyright © 2015 John Wiley & Sons, Ltd.     

壳聚糖和乳清分离蛋白在食品包装中的应用

综述了壳聚糖和乳清分离蛋白最新研究进展.壳聚糖薄膜是优良的抗菌性包装材料,乳清分离蛋白薄膜对氧气、芳香类和脂类物质的阻隔性非常好.壳聚糖涂层复合薄膜用于活性包装具有巨大的潜力.乳清分离蛋白涂层复合薄膜具有取代日前阻氧性合成包装材料的潜力.     

Microperforation of Three Common Plastic Films by Laser and Their Enhanced Oxygen Transmission for Fresh Produce Packaging

Three different plastic films of biaxially oriented polypropylene (BOPP), biaxially oriented polyethylene terephthalate (BOPET) and low‐density polyethylene (LDPE) were perforated using Nd‐YAG laser. Effects of laser pulse energy were examined by varying energies from 50 to 250 mJ where the pulse duration and pulse repetition were kept constant at 10 ns and 1 Hz, respectively. It was found that perforation diameters of all films increased with increasing pulse energies. Observed perforations were different among the three film types. Explanation was contributed to material inherent property and its interaction with laser. Incorporation of an inorganic filler (i.e. silica based anti‐blocking agent used in packaging film) of 0.5 wt% into the LDPE films (0.5Si‐LDPE) could improve perforation performance for LDPE. This was attributed to an increased thermal diffusivity of the 0.5Si‐LDPE film. Commercial BOPET and BOPP films containing 97 microholes/m² (hole diameter of ~100 µm) showed an improvement in oxygen transmission rates (OTR) of 18 and 5 times that of the neat films without perforation. In the case of perforated 0.5Si‐LDPE films having similar perforations of 97 microholes/m² and perforation diameter of 100 µm, a two‐fold increase of OTR was obtained. Gas transmission rates of the microperforated films were measured based on the static method. Measured OTR and CO₂TR values of the three films with varying perforation diameters in a range of ~40–300 µm were compared and discussed. Overall results clearly indicate that perforation by laser is an effective process in developing breathable films with tailored oxygen transmission property for fresh produce packaging. Copyright © 2014 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。     

Influence of sorbed vegetable oil and relative humidity on the oxygen transmission rate through various polymer packaging films

In this study, the effect of a vegetable oil on the oxygen barrier properties of different polymer packaging materials [i.e. amorphous polyethylene terephtalate (APET), polypropylene (PP) and high density polyethylene (HDPE)] was investigated. The influence of both relative humidity and the combination of relative humidity and sorbed oil on the oxygen transmission rate (OTR) was studied. Regardless of the relative humidity, the APET film remained an excellent oxygen barrier even after storage in rapeseed oil for 40 days. An increased OTR was observed in both the PP and HDPE films stored for 40 days in rapeseed oil. The OTR of the HDPE films was altered to a much greater extent than the OTR of the PP film. The OTR of the HDPE film was also significantly increased for films stored for 20 days in rapeseed oil. The increase in OTR of an HDPE film stored for 40 days in rapeseed oil was between 36 and 44%, depending on the relative humidity, compared to the OTR through the virginal polymer. The amount of oil sorbed by the polymer films used decreased in the following order: HDPE ? APET > PP.     

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.     

Numerical simulation of permeation through vacuum‐coated laminate films

The material usage in the packaging market of Germany has decreased over the last few years. This trend results from the substitution of heavy packages with light‐weight, flexible materials. In this context, aluminium foil‐based multilayer films have been partly replaced by metallized laminates in food packaging technology. Other coating materials, such as Al₂O₃ or SiO_x, are used where transparent films are desired. The disadvantage of these vacuum‐coated layers is the existence of pinholes which allow diffusion processes, in contrast to aluminium foil‐based multilayer films. In this study the barrier behaviour of vacuum coated laminate films was predicted by numerical simulation. The results are presented in terms of dimensionless parameters so that they may be transferred to analogous problems. This model provides a method to calculate the oxygen permeation through coated laminates. However, it is invalid for condensable gases such as water vapour. The simulation is suited for characterizing the influence of the compound structure on the barrier properties of vacuum coated laminate films. The results are verified by comparing the calculated with measured values. Copyright © 2002 John Wiley & Sons, Ltd.     

Study of mechanical properties,oxygen permeability and AFM topography of zein films plasticized by polyols

The use of plastic for packaging has grown extensively in recent years. In this context, biodegradable films can be a source of energy saving and an important issue for environmental protection. Zein protein (prolamin of corn) is one of the best biopolymers for edible film making and polyols are convenient plasticizers for biopolymers. Polyols (sorbitol, glycerol and mannitol) at three levels (0.5, 0.7 and 1g/g zein) were used as plasticizers and the tensile properties, oxygen permeability (OP) and AFM topography of zein films were studied. Films plasticized by sorbitol had a relatively higher ultimate tensile strength (UTS) than films containing glycerol and mannitol at low levels of plasticizers (0.25, 0.7g/g zein). There was no significant difference between the strain at break values (SB) of films plasticized by sorbitol and glycerol at low levels of plasticizers, while films plasticized by sorbitol had higher SB than the films containing glycerol and mannitol at a high level of plasticizer (1g/g zein). Pure zein films had low oxygen permeability (OP), and increasing the plasticizer level to 0.5g/g zein decreased OP values in films containing sorbitol and glycerol. Films containing sorbitol and mannitol had the lowest and highest OP values, respectively. AFM images were used to evaluate the surface morphology (qualitative parameter) and roughness (quantitative parameter) of zein films. Films plasticized by glycerol had smoother surfaces and a lower roughness parameter (Rq). No relationship between OP values and the roughness of the zein films was observed. Copyright © 2006 John Wiley & Sons, Ltd.     

大豆分离蛋白膜制备及改性研究的现状和应用

目的整理和归纳目前国内外关于大豆分离蛋白(Soy Protein Isolate,SPI)膜的制备方法及改性研究的最新研究成果,为将来制备高性能的该系列材料提供依据。方法归纳整理国内外文献,从文献中归纳SPI膜的基本性能和目前SPI膜的3种主流制备方法,并从力学性能、防潮性能、抑菌性能、阻氧阻湿性能等4个方面介绍SPI膜的改性研究现状,最后对SPI膜的应用情况进行归纳。结果 SPI具有来源广泛、价格低廉、环境友好等诸多优点。在对其进行改性后,由SPI制备薄膜的成膜性能、力学性能、防潮性能、抑菌性能、阻氧阻湿性能均有显著提高。结论对SPI膜进行有效改性后,其在保鲜包装、环保包装、可食用包装、风味食品包装等领域具有广泛且良好的发展前景。