Oxygen Transmission Rate Research Articles

Hybrid organic-inorganic coating with enhanced oxygen- and UV-barrier performance: Polyelectrolyte complex based on sodium alginate, poly (vinyl alcohol), and reconstructed layered double hydroxide

Organic-inorganic hybrid materials with high oxygen- and UV-barrier properties were developed using a polyelectrolyte complex comprising sodium alginate (SA), poly (vinyl alcohol) (PVA), and reconstructed layered double hydroxide (RLDH). These materials were applied to poly (ethylene terephthalate) (PET) as a barrier coating layer at a harsh drying temperature of 120 °C, similar to environments for the industrial coating process. The RLDH nanoplatelets within the coating matrix restricted the polymer chain mobility, elevating the glass transition temperature to 105.222–159.114 °C. Below RLDH 0.2 %, the apparent coating density significantly increased to 0.93–0.94 g/cm3. The embedded RLDH gave a tortuosity within the matrix, as evidenced by an intensified (003) diffraction peak in the XRD analysis. These structural alterations contributed to high oxygen- and UV-barrier performance. Notably, the PET/SA1.0PVA0.5RLDH0.2 film exhibited an extremely low oxygen transmission rate of <0.005 cm3/m2·day, with effectively blocking UV-A (62.41 %), -B (92.45 %), and -C light (100 %). Moreover, the susceptibility of the coated film to water vapor was mitigated by laminating cast polypropylene, achieving a water vapor transmission rate of 1.17 g/m2·day. Overall, the packaging materials with advanced oxygen-, water vapor-, and UV-barrier properties show great potential for practical applications in various sectors, including food packaging and medical/electrical devices.

Substrate Modifications for Stability Improvements of Flexible Perovskite Solar Cells

Flexible perovskite solar cells (fPSCs) prepared on flexible plastic substrates exhibit poor stability under illumination in ambient, due to inferior gas barrier properties of plastic substrates. Herein, we investigated effect of different modifications of the back surface of the substrate to improve stability under illumination in ambient. T80 under simulated solar illumination at maximum power point in ambient (ISOS‐L‐1) can be increased from 80 h to over 350 h with the deposition of a single layer (by spin‐coating or by atomic layer deposition (ALD)). While ALD layers resulted in the best T80 value and significant reduction of the oxygen transmission rate compared to other modifications even for very low film thickness (≈10 nm), a simple solution‐processed spin‐on‐glass barrier layer also enables significant (more than 4 times) improvement in device stability. This work illustrates the importance of barrier layers for decreasing the ingress of oxygen and moisture into fPSCs through the plastic substrate.

Impact of mutations in starch synthesis genes on morphological, compositional, molecular structure, and functional properties of potato starch.

Morphology, composition and molecular structure of starch directly affect the functional properties. This study investigated the morphological, compositional, and molecular structure properties of starch from starch branching enzyme gene (SBE) and granule-bound starch synthase gene (GBSS) mutated potato, and their associations with thermal, pasting, and film-making properties. SBE mutations were induced in native variety Desiree while GBSS mutations were herestacked to a selected SBE mutated parental line. Mutations in SBE resulted in smaller starch granules and higher amylose content, while GBSS mutations in the SBE background reduced amylose content. Mutations in SBE, particularly with GBSS mutations, significantly increased total phosphorus content. 31P NMR spectroscopy revealed higher proportions of C6-bound phosphate than of C3-bound phosphate in all studied lines. Amylopectin unit chain and internal chain distributions showed higher proportions of long chains in mutated lines compared with Desiree. These amylopectin long-chains were positively correlated with gelatinizationand, pasting temperatures, and temperature at peak viscosity. Short amylopectin chains showed positive correlations with breakdown viscosity, but negative correlations with the crystal melting temperature of retrograded starch. Total phosphorus content was positively correlated with the crystal melting temperature of retrograded starch. Starch from different lines was used to produce a series of potato starch films that differed in morphology and functional properties. A negative correlation was observed between Young's modulus of films and the long amylopectin-chain fraction. Thermal gravimetric analysis revealed highest thermal stability of Desiree starch films, followed by films from SBE-mutated high-amylose lines. Oxygen transmission rate and oxygen permeability analyses showed that films made with starch from selected GBSS and SBEs mutated line maintained comparable oxygen barrier properties to Desiree film. These insights on the impact of genetic mutations on starch properties indicate potential applications of in-planta starch modification for specific end-uses including packaging.

Physicochemical properties and pork preservation effects of lotus seed drill core powder starch-based active packaging films

Lotus seed drill core powder starch (LCPS)-based active packaging films incorporated with cellulose nanocrystals (CNC) and grapefruit essential oil-corn nanostarch Pickering emulsion (ECPE) were characterized, and their pork preservation effects were investigated in this study. In contrast with corn, potato and rice starches, LCPS showed higher amylose content, elliptical and circular shape with more uniform size distribution. Furthermore, LCPS film exhibited lower light transmittance, stronger tensile strength, and smaller elongation at break compared to the other starch films. Then, the LCPS film containing 4 % CNC and 9 % ECPE was fabricated which had stronger mechanical properties, lower water vapor permeability and oxygen transmission rate, and denser network structure. FTIR and XRD analyses also confirmed that CNC and ECPE were successfully implanted into the LCPS matrix without damaging the crystalline structure of LCPS. Herein, the LCPS/CNC/ECPE film exerted potential antibacterial activity against Escherichia coli and Staphylococcus aureus. Besides, packaging with this composite film significantly preserved the pork during cold storage via decreasing its juice loss rate, pH value, total number of colonies, total volatile base nitrogen and thiobarbituric acid reactive substance values. The present study will provide a theoretical basis for the application of LCPS as new biodegradable active films.

Evaluation limit of O2 permeability in barrier films by electrolytic oxygen pump

Packaging foods, medicines, and electronic devices and shielding them with barrier films to protect them from oxidation and degradation are crucial technologies for their long-term preservation. In this paper, a new evaluation device and the evaluation limit of oxygen transmission rate (OTR) in barrier films were described. The device was based on an O2 pump, consisting of the cathode reaction of a fuel cell (absorbing O2) and the anode reaction of water electrolysis (generating O2). By shielding the cathode with barrier films, the reaction current was strictly determined by the permeated O2 through the barrier film. OTRs in typical polymer films such as silicon rubber, polyethylene, and polyester were evaluated to confirm the method was consistent with conventional methods. The detection limit for high barrier films was examined and found to be approximately 10 cc/m2/day/atm at the present stage. The strategies to improve the detection limit were discussed.

Fabrication of biodegradable and cold-water-soluble starch/polyvinyl alcohol films as inner packaging materials of pesticides: Enhanced emulsification, dispersibility, and efficacy

Developing environmentally friendly film materials for packaging pesticides is significant yet challenging. The use of native starch for preparing inner packaging materials of pesticides is limited by its physicochemical properties. In this study, a novel strategy of synergetic mechanical activation (MA)-enhanced solid-phase esterification of starch and cooperative combination of starch and polyvinyl alcohol (PVA) was proposed to fabricate biodegradable and cold-water-soluble starch (St)/PVA films. The appropriate esterification of starch and favorable compatibility between starch and PVA contributed to the production of St/PVA films by the extrusion-blowing method. The as-prepared film with St/PVA ratio of 4:6 exhibited outstanding mechanical properties (tensile strengths of 21.0 MPa; elongation at break of 213.9 %), cold-water solubility (dissolution time of 90 s), and oxygen barrier performance (oxygen transmission rate of 1.41 cm3/(m2·day·bar)). The dissolved St/PVA films with amphiphilic groups were conducive to the emulsification of butachlor (a fat-soluble liquid pesticide) and the dispersibility of oxyfluorfen (a fat-soluble solid pesticide). Furthermore, a mechanism of the interaction between pesticides and the surface of weed leaves was proposed to reveal the enhanced efficacy of St/PVA films-packaged pesticides. The strategy based on MA-enhanced esterification and PVA blending is efficient to produce starch-based films suitable for inner packaging materials of pesticides.

Extending the Shelf Life of Atlantic Salmon (Salmo salar) with Sub-Chilled Storage and Modified Atmosphere Packaging in Recyclable Mono-Material Trays.

This study investigated the effect of sub-chilling whole gutted salmon and sub-chilled storage at -1 °C in modified-atmosphere packaging in two recyclable mono-material trays (CPET, HDPE). Quality parameters were measured, including water-holding properties, salt content, color, texture, lipid oxidation, and sensory and microbiological shelf life. The oxygen transmission rate was measured for the packages. Compared to traditional fish storage on ice, sub-chilling gave a 0.4% weight gain, better water-holding capacity, and higher salt content. The sub-chilled fish gave a significantly better sensory quality and microbiological shelf life of up to 49 days. Photobacterium was the dominating bacteria during storage. Salmon packaged in CPET trays had a higher drip loss than HDPE trays, but a lower rate of lipid oxidation (1-penten-3-ol). Our results showed the feasibility of significantly extending shelf life with sub-chilling, removing the need for ice. Moreover, using recyclable trays for packaging contributes to a circular economy without compromising food quality.

Dual Clay Nanobrick Wall Thin Films with High Oxygen Barrier at High Humidity

AbstractThin polymer‐based coatings with high oxygen barrier at elevated humidity are needed for the protection of food and organic electronic devices. Polyelectrolyte‐based thin films (deposited via layer‐by‐layer assembly) perform well at ambient humidity, but their performance typically dwindles as humidity increases due to their hydrophilic nature. Retention of their high barrier can be achieved through the addition of chemical crosslinkers or the introduction of inorganic platelets that create a nanobrick wall structure. In this study, a nanobrick wall barrier prepared with two types of clay, with a thickness less than 200 nm, is shown to reduce the oxygen transmission rate (OTR) of 179 µm polyethylene terephthalate to less than 0.016 cm3 m−2 day−1 atm−1. At 90% relative humidity (RH), a quadlayer barrier consisting of polyethylenimine, boehmite clay, poly(acrylic acid), and vermiculite clay maintains nearly 90% of its barrier performance at 0% RH (OTR = 0.019 cm3 m−2 day−1 atm−1). This study demonstrates the potential of dual clay thin film nanocomposites to protect various consumer goods at high humidity.

Pilot Scale Assessment of High-Pressure Processing (HPP) to Enhance Microbiological Quality and Shelf Life of Fresh Ready-to-Eat (RTE) Blue Crab Meat.

Blue crab (Callinectes sapidus) is a highly valuable wild fishery species of crab native to the waters of the western Atlantic Ocean and the Gulf of Mexico. The annual commercial production of live blue crabs is approximately 50,000 metric tons with a dockside value of USD 200 million. Presently the US blue crab processing industry sells crab meat in three basic forms: fresh crab meat, pasteurized crab meat, and frozen crab meat. By far "Fresh" is the most desirable form of crab meat. However, fresh crab meat has a limited shelf life. This study evaluated the effects of high-pressure processing (HPP) on enhancing the microbiological quality and shelf life of blue crab meat. Live blue crabs were pressure-cooked in a retort (≥115 °C for 4-6 min). The crab meat was handpicked, packed in plastic containers with seals, subjected to HPP treatment, and stored at 4 °C. Container integrity and water leakage issues were examined by observation in addition to weight comparison before and after HPP treatment; the shelf life of crab meat with and without HPP treatments was examined via microbiological tests and sensory evaluations. Results show that polypropylene containers sealed with 10K OTR (oxygen transmission rate) film could withstand high pressure without water leakage issues; HPP treatment at 600 MPa for 3 min could extend the shelf life of fresh, cooked, and handpicked crab meat from 6 days to 18 days based on the strictest APC (aerobic plate account) limit (APC ≤ 100,000 CFU/g). The sensory quality of the HPP-treated crab meat was well accepted throughout the 3-week storage period. The results support the use of HPP as an effective non-thermal processing technology to enhance the microbiological quality and extend the shelf life of fresh RTE blue crab meat.

Bio-inspired seaweed-based nanocomposite materials with excellent degradability and multifunctional barrier properties for green packaging

The widespread use of petroleum-based plastics brings potential hazards to the ecological environment. In order to solve this issue, the development of biodegradable materials with both high mechanical, barrier performances and food safety is imminent. In this work, a natural nacre-inspired seaweed-based nanocomposite material with the structure of “brick and mortar” is synthesized by rational assembling mica nanosheets in a mixture of glycerol and sodium alginate. The resultant SA/nano-mica film (1 wt% of phlogopite powder) shows high thermal stability (>180 °C) and exhibits great tensile strength of ∼ 16 MPa at ambient condition, surpassing some other reported nanocomposite materials (1.9–14.74 MPa). Meanwhile, the composite can be easily processed into different shapes for packaging applications, which could long-term preserve the freshness of foods owing to their strong ultraviolet (UV) shielding and gas barrier properties (UV transmittance of ∼ 4 % and oxygen transmission rates (100 µm) of ∼ 18.52 cc m−2 day−1 bar−1). Importantly, the material could completely degrade in soil within 15 days. These results indicate the great application prospect of seaweed-based nanocomposite materials in food packaging.

Bioactive Cellulose Nanopapers Impregnated with Cinnamon Essential Oil for Sustainable Antibacterial Packaging and Extended Shelf Life of Coriander Leaves

AbstractThis study introduces a novel approach by developing cellulose nanopapers derived from pineapple pomace and impregnated with cinnamon essential oil (CEO) in the range of 1–5 wt.%. This innovative material aims to enhance the shelf life of coriander leaves through antibacterial packaging. Comparative analyses encompassed structural, crystalline, morphological, physico‐mechanical, water barrier, permeability, and antibacterial properties against control samples. Incorporating CEO yielded a reduction in crystallinity index and tensile strength, attributed to a plasticizing effect. The addition of 5 wt.% CEO led to a remarkable 46% increase in elongation at break. Enhanced thermal stability, with a Tmax rise of 26 °C, is attributed to hydrogen bonding between CEO and cellulose molecules. The nanopapers exhibited notable reductions in oxygen and water vapor transmission rates (24% and 32% respectively) compared to control nanopapers. Impressive antibacterial activity against S. aureus and E. coli is observed. These developed nanopapers are applied as active packaging for coriander leaves, extending their shelf life by up to 3 and 15 days without and with refrigeration. Moreover, chlorophyll, carotenoid, and moisture content in coriander leaves stored with CEO‐loaded nanopapers remained akin to fresh leaves. Thus, this study presents an environmentally friendly antibacterial packaging solution with potential for sustainable application.

Development of a Skin Scaffold for Wound Healing Using a Polymer Blend

Native skin consists mainly of epidermal and dermal layers. Here in this work, we have constructed an artificial skin scaffold mimicking the bilayered structure of the native skin using electrospinning technique for wound healing. Polyurethane (PU) and Gelatin (Ge) were used for developing the epidermal layer and the dermal layer respectively. Ciprofloxacin HCl (Cip. HCl) a fluoroquinolone antibiotic was incorporated in both the layers for rapid wound healing. Morphology of the skin scaffold was studied using scanning electron microscopy (SEM) analysis and the chemical characterization was performed using FTIR spectroscopy. Water vapor transmission rate test and oxygen transmission rate test was conducted to evaluate the barrier properties of the scaffold. Thermal stability of the skin scaffold was evaluated using DSC and TGA while an understanding of the exudate absorbing capacity and degradation behavior of the scaffold was obtained from water absorption studies and in vitro degradation studies respectively. In vitro drug release study and drug release kinetics was explored to understand the release mechanism of Cip. HCl from the scaffold. Both the layers showed nano and micropores when analyzed using SEM. The dermal layer showed comparatively more water absorption capacity and degradation, hence providing a moist environment for the wound. The skin scaffold was permeable to water vapor and oxygen, and hence will speed up the process of wound healing. In vitro release for Cip. HCl showed a non-Fickian swelling type release with zero-order kinetics. Disk diffusion test conducted on the bilayers proved the antibacterial activity of the membrane. Hence the electrospun PU-Ge skin scaffold containing Cip. HCl is a promising candidate among modern day wound healing materials.

Polylactic Acid-Based Film Modified with Nano-Ag-Graphene-TiO2: New Film versus Recycled Film

The increase in the polymer-based materials needs has induced along the waste accumulation, thus argued higher interest in recycling. The study aims to assess the structural, morphological, mechanical resistance, physical–chemical and biochemical characteristics, as well as the preservative role during the curd cheese storage of a recycled polylactic acid (PLA)-based film modified with Ag-graphene-TiO2 nanostructured composite, obtained by recovering the composite from the used film, followed by its incorporation in new PLA. The breaking load of the recycled film was 24% lower than that of the new film and 10% higher than of the neat PLA. Differential scanning calorimetry (DSC) showed changes of the recycled PLA’s surface tension and crystallization degree in a greater extent than in the newly prepared film, revealing better incorporation of the recovered composite into the PLA matrix. Fourier transformed infrared spectroscopy showed the formation of C–O–Ti bridges between composite and PLA both in new and recycled film. Oxygen transmission rate (OTR) of the new and recycled film decreased by 33% and 45%, respectively, in comparison with reference PLA. The curd cheese was successfully stored in the recycled packaging; the organoleptic characteristics of cheese wrapped in recycled film were superior in comparison with the new film. The variation of fat and protein contents and mass loss was the lowest when the recycled film was used as packaging material. The study successfully showed the possibility to recover and recycle the used PLA-based films modified with inorganic nanocomposites.

Obtention and Study of Polyurethane-Based Active Packaging with Curcumin and/or Chitosan Additives for Fruits and Vegetables-Part I: Analysis of Morphological, Mechanical, Barrier, and Migration Properties.

Several polyurethane-formulated films with curcumin and/or chitosan additives for food packaging have been previously obtained. The study examines the effect of the additives on the film's morphological, mechanical, barrier, and migration properties. Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), water contact angle, thermogravimetric and differential thermal analysis (TGA and DTGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), oxygen transmission rate (OTR), water vapor transmission rate (WVTR), and the overall and specific migration tests were conducted. The results show that the presence of chitosan significantly increased the overall migration and mechanical properties, such as the elongation at break, tensile strength, and Young's modulus of most polyurethane formulations, while curcumin had a minor influence on the mechanical performance. Based on the results, formulations with curcumin but without chitosan are suitable for food packaging.

Seed Quality Behaviour Variation of Moth Bean during Storage in Different Packaging

An experiment was carried out in order to assess the behavior of the moth bean seed quality in 4 types of packaging including cloth, gunny, HDPE, and vacuum-packed bags for 18 months. After two months of storage, the moisture content of the seeds fluctuated greatly in cloth, gunny, and HDPE bags (conventional packaging) because these materials are pervious, but the moisture content of the seeds did not vary in vacuum packed bags as the polythene bag used for the vacuum package was thicker, had a lower water vapor and oxygen transmission rate. Further, seeds in conventional packaging’s developed bruchid infestations after 4 months of storage but no infestation was found in vacuum-packed bags until 18 months. The bruchid infestation caused the germination rate of the seeds to drop to less than 20%. In comparison to the initial state, even after 18 months of storage, there was little change in the parameters used for measuring seed quality (germination, total seedling length, seedling dry weight, moisture content, and protein content). Therefore, without the use of chemicals, moth bean seeds can be safely stored using vacuum packaging technology.

Renewable thermoplastic starch/sugar alcohol blends and their oxygen barrier application

AbstractFully renewable oxygen barrier thermoplastic starch (TPS)/sugar alcohol blown films were innovatively prepared by blending proper loadings of Erythritol (ET), Sorbitol (ST), and Lactitol (LT) and supercritical carbon dioxide (scCO2) assistance. The oxygen transmission rate (OTR) values of the properly prepared scCO2TPSxETy, scCO2TPSxSTy, and scCO2TPSxLTy films reduced to 4.3, 6.6, and 12.5 cm3/m2∙day∙atm, which are about 5–28 times smaller than those of the conventional TPS films reported in the literature. The free‐volume‐cavity characteristics (FVCC) and OTR detected for TPSxETy (or scCO2TPSxETy), TPSxSTy (or scCO2TPSxSTy), and TPSxLTy (or scCO2TPSxLTy) films diminished to a minimum, as their ET, ST and LT loadings came near an optimal value. Slightly smaller OTR and FVCC values were detected for scCO2TPSxETy, scCO2TPSxSTy, and scCO2TPSxLTy films than those of corresponding TPSxETy, TPSxSTy, and TPSxLTy films prepared without scCO2‐assistance. The smallest OTR and FVCC detected for the properly prepared TPSxETy (or scCO2TPSxETy), TPSxSTy (or scCO2TPSxSTy), and TPSxLTy (or scCO2TPSxLTy) films diminished with decreasing sugar alcohol's molecular weight. An essential result is that the OTR of the properly prepared scCO2TPSxETy film was merely 4.3 cm3/m2∙day∙atm, which is small enough to meet the demand of high oxygen barrier packaging application. Dynamic molecular relaxations detected for these films disclosed that ET, ST, and LT were compatible with TPS, as their loads were ≤ the optimum value. The distinctly reduced OTR and FVCC for these properly prepared films are partially attributed to the reinforced molecular interactions between sugar alcohol and TPS's hydroxyl groups when they were prepared with scCO2‐assistance, optimal sugar alcohol loading, and/or smaller sugar alcohol's molecular weight.Highlights High oxygen barrier thermoplastic starch/sugar alcohol blown films were prepared. The lowest oxygen transmission rate of the renewable film was 4.3 cm3/m2∙day∙atm. This oxygen transmission rate is qualified for high oxygen barrier application. Boosted oxygen barrier property was ascribed to the reduced free volume values.

How to get reliable oxygen transmission rate values for coated cardboards?

Coated papers have emerged as alternatives to petroleum-based and non-biodegradable plastics, particularly in packaging industries. Indeed, barriers brought by the coating layer, toward oxygen for example, allow better food preservation. This growing interest in the field of packaging has led to the need to characterize the mass transfer properties of these materials, particularly oxygen. Although methods and standards to characterize these parameters have been developed for plastic materials, none have been specifically adapted for coated cardboards. This paper evidences a so-called “edge effect” occurring when characterizing the oxygen transmission rate (OTR) of single-side coated cardboards. This leads to two significantly different OTR values depending on the material's side, cardboard, or polymer coating, exposed to the oxygen flux. Over- or under-estimated OTR can have a significant impact on food preservation. Therefore, avoiding edge effects is essential for obtaining accurate oxygen transmission rate value. This study focuses on one measurement method and two cardboard supports. Depending on the equipment used and sample properties, different methods can be used to prevent edge effects and must be investigated on a case-by-case basis.

A novel paper-based composite film with enhanced oxygen and water vapor barrier properties

Paper-based composite films have demonstrated significant potential in the field of packaging materials. However, the gas barrier properties of these films have been found to be less than satisfactory, primarily due to the inherent porosity and hydrophilic nature of cellulose-based paper. Consequently, the challenge of enhancing the gas barrier performance, particularly in relation to oxygen and water vapor, remains a formidable obstacle. In this study, drawing inspiration from the well-established multilayer composite model, which incorporates both organic and inorganic layers, an efficient strategy has been devised to enhance the gas barrier performance of paper-based packaging materials. The organic barrier layers in this approach utilize polyvinyl alcohol and polyacrylate. Meanwhile, the critical inorganic barrier layer is composed of functionalized SiO2@polydopamine nanoparticles (SiO2@PDA NPs). Importantly, due to the isotropic nature of the SiO2@PDA NPs, concerns related to the orientation control and exfoliation of 2D layered materials are alleviated within this system. The introduction of a crosslinker, 3-aminopropyl triethoxysilane, serves to bridge the gap between SiO2@PDA NPs, facilitating the tight concatenation of NPs through Schiff base or Michael addition reactions. Utilizing coating technology, a paper-based multilayer film was fabricated. As a result, the oxygen transmission rate of the composite film was substantially reduced to 0.3077 cm3/cm2·24 h·0.1 MPa, and the water vapor transmission rate was lowered to 4.1109 g/m2·24 h. Significantly, these composite films exhibit exceptional water resistance and mechanical properties, rendering them highly suitable for the packaging of a wide range of sensitive products, including food items, pharmaceuticals, electronic devices, and other gas-sensitive products.

Modelling the respiration rate of dabai fruit (Canarium odontophyllum Miq.) stored in different packaging films

Dabai (Canarium odontophyllum Miq.) is a highly nutritious fruit that has a huge potential to be marketed both locally and globally. However, the lack of promotion leads to an oversupply during peak season, thus reducing its market price. Proper handling and packaging are therefore necessary to maintain the quality and extend the shelf life of dabai. In the present work, nylon film with an oxygen transmission rate (OTR) of 55 cc/m2/day and water vapour transmission rate (WVTR) of 334 g/m2/day; polyethylene terephthalate (PET) film with an OTR of 90 cc/m2/day and WVTR of 35 g/m2/day; and low-density polyethylene (LDPE) film with an OTR of 8000 cc/m2/day and WVTR of 200 g/m2/day were used to pack dabai and stored at 5°C for 14 d. All films had a dimension of 200 × 300 mm, and a thickness of 0.01 μm. It was found that dabai maintained its hue angle (h°) values within the dark purple region (299.73° to 338.64°) and its lightness (L*) values throughout storage. However, the colour intensity (chroma) significantly changed (p &lt; 0.05) between different films throughout storage (p &lt; 0.05). The control sample had the most significant decrease in firmness and weight (p &lt; 0.05) between day 0 and 14, followed by the samples stored in PET, LDPE, and nylon. Whereas the samples in LDPE demonstrated the lowest respiration rate as compared to nylon and PET. The uncompetitive Michaelis-Menten equation model was used to model the respiration rate of dabai. Results showed that all films obtained good fit (R2 of near to 1). Additionally, the mean relative percentage (E%) was less than 10%, thus indicating that the data were suitable for real-time application.

Effect of super critical carbon dioxide and alkali treatment on oxygen barrier properties of thermoplastic starch/poly(vinyl alcohol) films

Abstract Sustainable oxygen barrier thermoplastic starch (TPS)/polyvinyl alcohol (PVA) blown films were successfully prepared by blending proper PVA loads during NaOH-treating and supercritical carbon dioxide (scCO2) assisted processing. The NaOH-treated TPS or scCO2TPS films showed smaller free-volume-cavity characteristics (FVCC) and oxygen transmission rate (OTR) than those of TPS (or scCO2TPS) prepared without proper alkali-treatment. Smaller OTR and FVCC values were detected for NaOH-treated scCO2TPS films than those of NaOH-treated TPS films prepared without scCO2-assistance. All OTR and FVCC values detected for proper alkali-treated scCO2TPS y PVA z films diminished distinctly to a smallest value, when their PVA loads came near a solubility limit value of 27.5 wt%. An essential result is that the OTR of the optimal NaOH-treated scCO2TPS y PVA z film is merely 3.1 cm3/m2 day atm, which meets the requirement of high oxygen barrier plastics. Dynamic molecular relaxations and WAXD patterns detected for proper NaOH-treated scCO2TPS y PVA z films disclosed that PVA was compatible with TPS, as PVA loads were ≤ the solubility limit value. The distinctly reduced OTR and FVCC detected for optimal NaOH-treated scCO2TPS y PVA z films are partially attributed to the reinforced molecular interactions between hydroxyl groups of TPS and PVA, as they were blended with proper PVA loads during their alkali-treating and scCO2-aid processing.