Permeation of Mineral Oil Components from Cardboard Packaging Materials through Polymer Films

Mineral oil migration from cardboard packaging into foodstuffs is recognized as a serious problem for the consumers. Within this study, a fast automated method for the determination of mineral oil permeation through barrier films was developed. The method is using 15 defined standard substances representing mineral oil chemistry instead of complex mineral oil mixtures. The developed method can be used for the evaluation of the barrier properties for polymer films regarding mineral oil components from paper and cardboard packaging materials. For all investigated permeants and polymer films, the logarithm of the permeation rates and the logarithm of the vapour pressure result in a linear correlation. The correlation can be used to compare the permeation properties of different barrier films. From the results of this study, it can be concluded that 12 µm oriented polyethylene terephthalate or 15 µm oriented polyamide are effective barriers towards mineral oil components. The barrier effect of pure polyolefin films is negligibly poor because the permeation is too fast and the lag time is in the range of a few hours at 40°C. As a consequence, the migration of mineral oil components from cardboard can be significantly reduced if inner layers of good barrier materials such as polyethylene terephthalate or polyamide are used. Copyright © 2012 John Wiley & Sons, Ltd.     

Antioxidant Properties of Selected Plant Extracts and Application in Packaging as Antioxidant Cellulose‐Based Films for Vegetable Oil

Selected plant extracts including cinnamon, clove, ginger, green tea and thyme were investigated for their antioxidant activity by using both β‐carotene‐linoleate bleaching agar well diffusion and β‐carotene‐linoleate bleaching broth assays, and for radical scavenging activity against free radicals using a 2,2‐diphenyl‐1‐picrylhydrazyl assay. Undiluted plant extracts (except ginger oil) showed a yellow zone of β‐carotene ranging from 15.3 to 38.2 mm in diameter. At a concentration of 50 μL mL^‐1, thyme yielded the highest antioxidant activity (260%), followed by ginger (254%), cinnamon (108%), clove (106%) and green tea (101%), respectively. Conversely, at a plant extract concentration of 0.39 μL mL^‐1 solution in ethanol, green tea yielded the highest radical scavenging activity (94.3%), followed by clove (93.4%), cinnamon (91.1%), thyme (30.4%) and ginger (8.29%), respectively. The minimum oxidative bleaching inhibitory concentrations (MOBICs) of these plant extracts were determined using a β‐carotene‐linoleate bleaching broth dilution assay ranging from 0.195 to 50 μL mL^‐1. The MOBICs of plant extracts in a range of 0.195–1.56 μL mL^‐1 could reveal an ability to inhibit the oxidation of β‐carotene‐linoleate broth. Cellulose‐based film containing cinnamon, clove or green tea showed positive activity against β‐carotene‐linoleate oxidation and 2,2‐diphenyl‐1‐picrylhydrazyl radicals. Protective effects of plant extracts incorporated in cellulose‐based pouches in stabilizing soybean oil were tested by measuring their peroxide values and free fatty acid contents during accelerated storage. Green tea‐incorporated cellulose‐based pouches exhibited stronger antioxidant properties in soybean oil than do butylated hydroxyanisole‐incorporated cellulose‐based pouches. This study showed the potential use of plant extracts as antioxidants for food packaging application. Copyright © 2011 John Wiley & Sons, Ltd.     

Novel Test Approach for Evaluating and Modelling Barrier Properties of Food Contact Materials Against Mineral Oil Contaminants

A method for testing the mineral oil barrier properties of packaging materials has been developed as a response for the concerns on contamination of food by mineral oil compounds. The aim was to provide an efficient tool to evaluate packaging materials with respect to this. The method is a modification of the so‐called cup test using model compounds comparable with mineral oil components with different length and configuration of the hydrocarbon chain. The model compounds are introduced in the gas phase as penetrants. The absorbed amounts, which have migrated through the barrier, are analysed from a food simulant or powdered sugar. The method has been validated for coated and non‐coated boards. Compared with folding boxboard without polymer coating, polyethylene terephthalate‐coated board reduces the amount of the C16 compound in food simulant after 7‐day tests by a factor of 30. An extended migration model describing sorption mechanisms to both food simulant and fibres in the packing material has been developed. The model simulations for folding boxboard indicate that fibres absorb a significant proportion of the compounds when molecular weight increases. This retards the migration significantly compared with the speed expected by diffusion mechanism only. Copyright © 2016 John Wiley & Sons, Ltd.     

Antimicrobial Activity of Cinnamaldehyde and Eugenol and Their Activity after Incorporation into Cellulose‐based Packaging Films

Cinnamaldehyde and eugenol were investigated for their antimicrobial activity against 10 pathogenic and spoilage bacteria and three strains of yeast, using an agar‐well diffusion assay. The minimum inhibitory concentrations (MICs) of these compounds were determined using an agar dilution method. Finally, cinnamaldehyde‐incorporated and eugenol‐incorporated methyl cellulose films were prepared to obtain active antimicrobial packaging materials. These antimicrobial cellulose‐based packaging films were investigated for antimicrobial activity against target microorganisms using both an agar‐disc diffusion technique and a vapour diffusion technique. At a concentration of 50 µl/ml, cinnamaldehyde and eugenol revealed antimicrobial activity against all test strains. They showed zones of inhibition, ranging from 8.7 to 30.1 mm in diameter. Eugenol and cinnamaldehyde possessed ‘moderate?strong inhibitory’ and ‘strong?highly strong inhibitory’ characteristics, respectively. With MICs of 0.78?50 µl/ml, cinnamaldehyde and eugenol also inhibited the growth of all test microorganisms. Among the test microorganisms, Aeromonas hydrophila and Enterococcus faecalis were the most sensitive to cinnamaldehyde and eugenol. Cinnamaldehyde showed lower MICs against all test strains than those of eugenol. In an agar‐disc diffusion assay, cellulose‐based film containing cinnamaldehyde or eugenol totally failed to exhibit a clear inhibitory zone. However, it showed positive activity against all selected test strains in terms of size and enumeration of microbial colonies in a vapour diffusion assay. This study shows the potential use of cinnamaldehyde and eugenol for application in antimicrobial packaging film or coating. Copyright © 2011 John Wiley & Sons, Ltd.     

Barriers against the Migration of Mineral Oil from Paperboard Food Packaging: Experimental Determination of Breakthrough Periods

A method is described for determining the breakthrough periods through various types of potential functional barriers. A donor pack with a sheet of paper containing the test migrant(s) was tightly fixed to one side of the barrier. It included a blank sheet of paper as a spacer to rule out wetting contact between the donor and the barrier. A polyethylene film acted as a receptor on the other side. Periodically, a piece of the receptor film was analysed for the test migrants broken through the barrier. As benchmarks, periods were extrapolated for 1% and 10% breakthrough compared with equilibration. Tests were performed at 60°C, 40°C and ambient temperature. Acceleration by increased temperature gave reasonably adequate results for polyethylene but too short breakthrough periods for polypropylene, owing to structural changes in the polymer. The donor pack also included Sudan red 2, which is of sufficient volatility to migrate through the gas phase. It enabled visual control for gaps and holes in the barrier layers or cracks, e.g. from manipulation (such as bends or scratches), by red spots in the tested material behind the barrier or in the receptor film. Breakthrough data for mineral oil of the type typically used in cold‐set offset printing inks are provided for a selection of materials. Polyethylene terephthalate and polyamide showed no breakthrough for a period corresponding to 6.9 years. Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

Visual Appearance of Chiral Nematic Cellulose‐Based Photonic Films: Angular and Polarization Independent Color Response with a Twist

Hydroxypropyl cellulose (HPC) is a biocompatible cellulose derivative capable of self‐assembling into a lyotropic chiral nematic phase in aqueous solution. This liquid crystalline phase reflects right‐handed circular polarized light of a specific color as a function of the HPC weight fraction. Here, it is demonstrated that, by introducing a crosslinking agent, it is possible to drastically alter the visual appearance of the HPC mesophase in terms of the reflected color, the scattering distribution, and the polarization response, resulting in an exceptional matte appearance in solid‐state films. By exploiting the interplay between order and disorder, a robust and simple methodology toward the preparation of polarization and angular independent color is developed, which constitutes an important step toward the development of real‐world photonic colorants.     

Synthesis of 2D Metal Chalcogenide Thin Films through the Process Involving Solution‐Phase Deposition

2D metal chalcogenide thin films have recently attracted considerable attention owing to their unique physicochemical properties and great potential in a variety of applications. Synthesis of large‐area 2D metal chalcogenide thin films in controllable ways remains a key challenge in this research field. Recently, the solution‐based synthesis of 2D metal chalcogenide thin films has emerged as an alternative approach to vacuum‐based synthesis because it is relatively simple and easy to scale up for high‐throughput production. In addition, solution‐based thin films open new opportunities that cannot be achieved from vacuum‐based thin films. Here, a comprehensive summary regarding the basic structures and properties of different types of 2D metal chalcogenides, the mechanistic details of the chemical reactions in the synthesis of the metal chalcogenide thin films, recent successes in the synthesis by different reaction approaches, and the applications and potential uses is provided. In the last perspective section, the technical challenges to be overcome and the future research directions in the solution‐based synthesis of 2D metal chalcogenides are discussed.     

Bounds for quantities of interest and adaptivity in the element‐free Galerkin method

A novel approach to implicit residual‐type error estimation in mesh‐free methods and an adaptive refinement strategy are presented. This allows computing upper and lower bounds of the error in energy norm with the ultimate goal of obtaining bounds for outputs of interest. The proposed approach precludes the main drawbacks of standard residual‐type estimators circumventing the need of flux‐equilibration and resulting in a simple implementation that avoids integrals on edges/sides of a domain decomposition (mesh). This is especially interesting for mesh‐free methods. The adaptive strategy proposed leads to a fast convergence of the bounds to the desired precision. Copyright © 2008 John Wiley & Sons, Ltd.     

Mechanical,Barrier, Optical Properties and Antimicrobial Activity of Edible Films Prepared from Silver Carp Surimi Incorporated with ε‐Polylysine

The effects of incorporating ε‐polylysine (ε‐PL) on mechanical, barrier, optical properties and the antimicrobial activity of edible films from silver carp surimi were investigated. The mechanical properties of surimi films could be improved using ε‐PL below the level of 0.15% in surimi film‐forming solutions, whereas these slightly declined with increasing addition of ε‐PL. However, accelerated polymerization of surimi myosin heavy chain by the addition of ε‐PL was too low to be observed from sodium dodecyl sulfate polyacrylamide gel electrophoresis patterns. It is of interest to notice that surimi films containing ε‐PL revealed a wide range of antimicrobial activity, especially against gram‐positive bacteria. For preservation of fresh fish meats with the help of edible films, the increase of total viable counts and total volatile basic nitrogen values was suppressed during storage at 4°C, indicating that the application of surimi films containing ε‐PL could prolong the shelf life of fresh fish meats. Copyright © 2012 John Wiley & Sons, Ltd.     

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.