Graphene Oxide Bionanocomposite Coatings with High Oxygen Barrier Properties

Development of a Biopolymer-Based Anti-Fog Coating with Sealing Properties for Applications in the Food Packaging Sector

The quest for sustainable and functional food packaging materials has led researchers to explore biopolymers such as pullulan, which has emerged as a notable candidate for its excellent film-forming and anti-fogging properties. This study introduces an innovative anti-fog coating by combining pullulan with poly (acrylic acid sodium salt) to enhance the display of packaged food in high humidity environments without impairing the sealing performance of the packaging material-two critical factors in preserving food quality and consumers' acceptance. The research focused on varying the ratios of pullulan to poly (acrylic acid sodium salt) and investigating the performance of this formulation as an anti-fog coating on bioriented polypropylene (BOPP). Contact angle analysis showed a significant improvement in BOPP wettability after coating deposition, with water contact angle values ranging from ~60° to ~17° for formulations consisting only of poly (acrylic acid sodium salt) (P0) or pullulan (P100), respectively. Furthermore, seal strength evaluations demonstrated acceptable performance, with the optimal formulation (P50) achieving the highest sealing force (~2.7 N/2.5 cm) at higher temperatures (130 °C). These results highlight the exceptional potential of a pullulan-based coating as an alternative to conventional packaging materials, significantly enhancing anti-fogging performance.

Fabrication and characterization of biomimetic plant cuticles from pullulan - graphene oxide (PU-GO) and beeswax - stearic acid (BW-SA) for Citrus Limon Rosso preservation

Inspired by the natural plant cuticles, a novel strategy was proposed for the fabrication of biomimetic plant cuticles from pullulan-graphene oxide (PU-GO) and beeswax-stearic acid (BW-SA), which could serve as hydrophilic polysaccharides and hydrophobic waxes, respectively. PU-GO and PU-GO/BW-SA in different GO concentrations (0, 10, 30 and 50 μg/mL) were prepared, and their structural characteristics and basic properties were investigated. Results showed that PU-GO/BW-SA possessed a hydrophilic layer and a hydrophobic structure similar to the structure of natural plant cuticles. The incorporation of GO enhanced the barrier properties of the films and PU-GO/BW-SA showed a higher contact angle, lower tensile strength and higher barrier properties compared with PU-GO. In addition, PU-GO/BW-SA in 10 μg/mL GO concentration (PU-GO10/BW-SA) possessed the lowest WVP (7.2 × 10-7 g/(m h Pa)) and a contact angle (93.78°) similar to natural plant cuticles. Applications in Citrus Limon Rosso further proved the potential of PU-GO10/BW-SA as a biomimetic plant cuticle in fruit preservation.

Review of polymer technologies for improving the recycling and upcycling efficiency of plastic waste

Human society has become increasingly reliant on plastic because it allows for convenient and sanitary living. However, recycling rates are currently low, which means that the majority of plastic waste ends up in landfills or the ocean. Increasing recycling and upcycling rates is a critical strategy for addressing the issues caused by plastic pollution, but there are several technical limitations to overcome. This article reviews advancements in polymer technology that aim to improve the efficiency of recycling and upcycling plastic waste. In food packaging, natural polymers with excellent gas barrier properties and self-cleaning abilities have been introduced as environmentally friendly alternatives to existing materials and to reduce food-derived contamination. Upcycling and valorization approaches have emerged to transform plastic waste into high-value-added products. Recent advancements in the development of recyclable high-performance plastics include the design of super engineering thermoplastics and engineering chemical bonds of thermosets to make them recyclable and biodegradable. Further research is needed to develop more cost-effective and scalable technologies to address the plastic pollution problem through sustainable recycling and upcycling.

Green Coating Polymers in Meat Preservation

Edible coatings, including green polymers are used frequently in the food industry to improve and preserve the quality of foods. Green polymers are defined as biodegradable polymers from biomass resources or synthetic routes and microbial origin that are formed by mono- or multilayer structures. They are used to improve the technological properties without compromising the food quality, even with the purpose of inhibiting lipid oxidation or reducing metmyoglobin formation in fresh meat, thereby contributing to the final sensory attributes of the food and meat products. Green polymers can also serve as nutrient-delivery carriers in meat and meat products. This review focuses on various types of bio-based biodegradable polymers and their preparation techniques and applications in meat preservation as a part of active and smart packaging. It also outlines the impact of biodegradable polymer films or coatings reinforced with fillers, either natural or synthesized, via the green route in enhancing the physicochemical, mechanical, antimicrobial, and antioxidant properties for extending shelf-life. The interaction of the package with meat contact surfaces and the advanced polymer composite sensors for meat toxicity detection are further considered and discussed. In addition, this review addresses the research gaps and challenges of the current packaging systems, including coatings where green polymers are used. Coatings from renewable resources are seen as an emerging technology that is worthy of further investigation toward sustainable packaging of food and meat products.

Enzymatic Hydrolysis of Bacterial Cellulose for the Production of Nanocrystals for the Food Packaging Industry

Bacterial cellulose nanocrystals (BCNCs) obtained by enzymatic hydrolysis have been loaded in pullulan biopolymer for use as nanoparticles in the generation of high-oxygen barrier coatings intended for food packaging applications. Bacterial cellulose (BC) produced by Komagataeibacter sucrofermentans was hydrolyzed by two different enzymatic treatments, i.e., using endo-1,4-β-glucanases (EGs) from Thermobifida halotolerans and cellulase from Trichoderma reesei. The hydrolytic activity was compared by means of turbidity experiments over a period of 145 h, whereas BCNCs in their final state were compared, in terms of size and morphology, by atomic force microscopy (AFM) and dynamic light scattering (DLS). Though both treatments led to particles of similar size, a greater amount of nano-sized particles (≈250 nm) were observed in the system that also included cellulase enzymes. Unexpectedly, transmission electron microscopy (TEM) revealed that cellulose nanoparticles were round-shaped and made of 4–5 short (150–180 nm) piled whiskers. Pullulan/BCNCs nanocomposite coatings allowed an increase in the overall oxygen barrier performance, of more than two and one orders of magnitude (≈0.7 mL·m⁻²·24 h⁻¹), of pure polyethylene terephthalate (PET) (≈120 mL·m⁻²·24 h⁻¹) as well as pullulan/coated PET (≈6 mL·m⁻²·24 h⁻¹), with no significant difference between treatments (hydrolysis mediated by EGs or with the addition of cellulase). BCNCs obtained by enzymatic hydrolysis have the potential to generate high oxygen barrier coatings for the food packaging industry.

Improving the Performance of Feather Keratin/Polyvinyl Alcohol/Tris(hydroxymethyl)Aminomethane Nanocomposite Films by Incorporating Graphene Oxide or Graphene

In this study, feather keratin/polyvinyl alcohol/tris(hydroxymethyl)aminomethane (FK/PVA/Tris) bionanocomposite films containing graphene oxide (GO) (0.5, 1, 2, and 3 wt%) or graphene (0.5, 1, 2, and 3 wt%) were prepared using a solvent casting method. The scanning electron microscopy results indicated that the dispersion of GO throughout the film matrix was better than that of graphene. The successful formation of new hydrogen bonds between the film matrix and GO was confirmed through the use of Fourier-transform infrared spectroscopy. The tensile strength, elastic modulus, and initial degradation temperature of the films increased, whereas the total soluble mass, water vapor permeability, oxygen permeability, and light transmittance decreased following GO or graphene incorporation. In summary, nanoblending is an effective method to promote the application of FK/PVA/Tris-based blend films in the packaging field.

Transparent Pullulan/Mica Nanocomposite Coatings with Outstanding Oxygen Barrier Properties

This study presents a new bionanocomposite coating on poly(ethylene terephthalate) (PET) made of pullulan and synthetic mica. Mica nanolayers have a very high aspect ratio (α), at levels much greater than that of conventional exfoliated clay layers (e.g., montmorillonite). A very small amount of mica (0.02 wt %, which is ϕ ≈ 0.00008) in pullulan coatings dramatically improved the oxygen barrier performance of the nanocomposite films under dry conditions, however, this performance was partly lost as the environmental relative humidity (RH) increased. This outcome was explained in terms of the perturbation of the spatial ordering of mica sheets within the main pullulan phase, because of RH fluctuations. This was confirmed by modelling of the experimental oxygen transmission rate (OTR) data according to Cussler’s model. The presence of the synthetic nanobuilding block (NBB) led to a decrease in both static and kinetic coefficients of friction, compared with neat PET (≈12% and 23%, respectively) and PET coated with unloaded pullulan (≈26% reduction in both coefficients). In spite of the presence of the filler, all of the coating formulations did not significantly impair the overall optical properties of the final material, which exhibited haze values below 3% and transmittance above 85%. The only exception to this was represented by the formulation with the highest loading of mica (1.5 wt %, which is ϕ ≈ 0.01). These findings revealed, for the first time, the potential of the NBB mica to produce nanocomposite coatings in combination with biopolymers for the generation of new functional features, such as transparent high oxygen barrier materials.