Barriers and Chemistry in a Bottle: Mechanisms in Today’s Oxygen Barriers for Tomorrow’s Materials

Biocompatible, Biodegradable, and Antimicrobial Food Packaging Film from Polylactic Acid and Biogenic Vaterite CaCO3-Ag Hybrid

Developing biocompatible and biodegradable materials for food packaging is crucial for addressing environmental concerns and ensuring food safety. In this study, we present a novel food packaging film composed of poly(lactic acid) (PLA) and biogenic vaterite CaCO3-Ag hybrid microspheres. A non-solution technique was employed to prepare these films, ensuring the sustainability and simplicity of the production process. X-ray diffraction and infrared spectroscopy analyses confirmed the stability and compatibility of the vaterite CaCO3-Ag microspheres within the PLA matrix. Cytotoxicity tests using human dermal fibroblast cells demonstrated complete biocompatibility of the films, even at high concentrations. Antimicrobial efficacy was assessed through minimum inhibitory concentration (MIC) testing, which demonstrated that PLA film containing 7 wt% vaterite CaCO3-Ag hybrids effectively inhibited both gram-positive and gram-negative bacteria at concentrations as low as ≤0.067 g/mL. Mechanical testing showed that the modulus and strength of PLA film increased significantly with the embedding of 5 wt% of vaterite CaCO3-Ag hybrid, reaching a maximum of 5.63 ± 1.51 GPa and 48.07 ± 13.81 MPa, respectively. Thermal analysis indicated improved thermal stability with the addition of the microspheres. Synchrotron X-ray absorption spectroscopy confirmed the stability of the vaterite structure and the presence of both Ag0 and Ag+ species after embedding in PLA matrix. The composite films exhibited improved oxygen and water vapor barrier properties, making them suitable for packaging applications. These findings highlight the potential of PLA-vaterite CaCO3-Ag hybrid films as sustainable and effective food packaging materials.

Structure-property relationships in shellac-coated paper: impact of coating parameters on high-barrier bio-based packaging applications

Paper coated with bio-based materials has attracted significant interest as an alternative to plastic-based materials for food packaging, with poor moisture barrier of coated paper posing a challenge to broader applications. Shellac is a promising biopolymer because of its low cost, biodegradability, and wide approval as a food additive and food contact material. In this work, we have systematically studied the role of shellac concentration in butanol and the number of coatings on coated paper's moisture and oil barrier properties. We investigated surface, physicochemical, and thermal properties of coated paper to elucidate specific interactions between shellac and paper substrate and characterize coating morphology, and their effect on barrier properties of coated paper. We found that every layer of coating resulted in an improvement in surface properties, with porosity decreasing by 90 % and surface roughness decreasing by 80 % in a single coat of 15 % (w/w) shellac solution. A low concentration of shellac (7.5 % (w/w)) was found to be less effective in improving barrier properties compared to the highest shellac concentration of 15 % (w/w) used in our study, but still caused a significant increase in the GSM (change in coated weight (g.m-2)). Four coatings of the 15 % (w/w) shellac solution resulted in a water vapor transmittance rate (WVTR) of 56 g m-2 day-1, a water barrier (COBB 180) of 1 g m-2, and an oil barrier (KIT) of 12. These results meet the strictest requirements for very high-barrier packaging applications.

Evaluation of perforation-mediated modified atmosphere packaging for the commercialization of bulk purple passion fruit under refrigeration

Modified atmosphere packaging (MAP) is widely used to preserve fresh fruits. In the case of exporting products in bulk formats (2-5 kg), perforated MAP can help extend shelf life if appropriately configured to reach suitable gas levels. This study evaluated the configuration of a perforated MAP system for purple passion (Passiflora edulis Sims) fruits based on modeling and simulation of changes in gas levels within the package headspace and experimental data on the respiration and transpiration of the fruits. For this evaluation, perforation-mediated multilayer bags made of polyamide and low-density polyethylene were adjusted to preserve 2 kg of purple passion fruits. The number of perforations made in the bags was predefined by performing predictive calculations to reach favorable gas levels in the packaging headspace. Subsequently, storage tests were conducted at the laboratory level (6 and 17 ± 1°C) and then at the pilot level (6 ± 2 and 17 ± 3°C), obtaining steady molar fractions of O2 of 0.122-0.128 and CO2 of 0.098-0.100 and shelf life of 36 days for the fruits packaged at 6°C. Additionally, the accumulated weight loss of the fruits was monitored, obtaining values close to those previously modeled. The pre-configuration of the perforations resulted in suitable O2 and CO2 levels in the MAP, achieving up to 36 days of shelf life at 6°C and 24 days at 17°C. Likewise, moisture permeation through the bags resulted in low condensation with fruit weight losses of 4.8% at 6°C after 55 days in the pilot test. PRACTICAL APPLICATION: This study evaluated using perforated PA/LDPE multilayer bulk bags (2 kg) to preserve purple passion fruits. The package was preconfigured (with a predefined number of perforations necessary to achieve favorable levels of O2, CO2, and humidity) and was compared against a commercial factory-made perforated package. By performing predictive calculations to define a suitable number of perforations, it was possible to regulate the respiration and transpiration of the packaged fruit to increase its shelf life under controlled and real conditions. This approach can be extended to any bulk-packaged fruit, and it can help select, design, and develop breathable packages that prevent decay.

Crystallinity Reconstruction of Squid-Pen Chitosan into Mechanically Robust and Multifunctional Bionanocomposite Food Packaging Film

First, we explore the effect of bioacids on the film processing of preprocessed, i.e., deacetylated, chitosan (d-chitosan with molecular weight of 1,000,000 kDa), using monocarboxylic acid (acetic acid), dicarboxylic acid (malic acid), and tricarboxylic acid (citric acid) as model weak acidic solvents to destabilize the hydrogen bonding and transform crystal structures into film. Second, we investigate the chemical and physical toughening effect in the bionanocomposite film composed of cross-linkable multicarboxilic acid, i.e., succinic acid (SA). In doing so, the addition of glycerol as a plasticizer can increase polymer chain mobility, making the biocomposite film more ductile and flexible. The addition of CNC also enhances the tensile strength (41.6%), swelling (43.47%), and oxygen barrier properties (38.81%), as well as significantly improves UV light barrier. The excellent antibacterial properties (99.9% efficiency against S. aureus and K. pneumoniae) of the prepared biocomposite films are found to be independent of the presence of glycerol or CNC. Third, the development of film processability under an industrially relevant process is also demonstrated by doctor blade method. It is found that film processability of the squid-pen's chitosan bionanocomposite can straightforwardly be compatible with and improvable in the presence of poly(vinyl alcohol) employed as a model biodegradable processing aid.

Mechanical properties, sustained release, and oxygen scavenging properties of nanocomposite films loaded with bimetallic nanoparticles (Fe2O3/TiO2) in extra virgin olive oil

The aim of this study was the synthesis of bimetallic nanoparticles based on Fe2O3/TiO2 and its use in the poly(lactic acid) (PLA) films as an oxygen scavenger in extra virgin olive oil (EVOO) packaging. Bimetallic nanocomposites were prepared by two different precipitation methods (precipitation with ammonia and sodium hydroxide). The characteristics of bimetallic nanoparticles precipitated with sodium hydroxide (Na-Ti0.01Fe0.048O0.08) and bimetallic nanoparticles precipitated with ammonia (NH-Ti0.01Fe0.022O0.09) were compared. Relative amounts of elements in bimetallic nanocomposites and their morphological characteristics were determined using field emission scanning electron microscopy coupled with energy-dispersive X-ray spectrometer. Porosity volume and surface area of bimetallic nanoparticles were calculated using adsorption-desorption isotherms and the Brunauer-Emmett-Teller method. The formation/characterization of bimetallic nanoparticles and their location in the matrix of PLA-based nanocomposite film was studied using X-ray diffraction and Fourier transform infrared. In nanocomposite films based on PLA, bimetallic nanoparticles lead to better oxidative stability (peroxide value, p-anisidine index, K232, and K270) of the EVOO and oxygen scavenging during storage compared to free nanoparticles. Mechanical properties of nanocomposite films were improved due to bimetallic nanoparticles, which were better for Na-Ti0.01Fe0.048O0.08. In vitro release modeling of the bimetallic nanoparticles in EVOO proved that Fickian diffusion is the dominant mechanism, and the Peleg model was the best description of the release behavior of nanoparticles.

Effect of Storage Technologies on Postharvest Insect Pest Control and Seed Germination in Mexican Maize Landraces

Smallholder farmers who grow maize landraces face important challenges to preserve their seed biodiversity from one season to another. This study was carried out in the central highlands of Mexico to compare the effectiveness of two seed storage practices-specifically, polypropylene woven bags (farmers' conventional practice) vs. hermetic containers-for minimizing seed losses and maintaining germination. Four Mexican landraces were stored for three and six months. Data on moisture content and kernel damage were collected at the beginning and the end of the storage period. Pest-free samples collected were also analyzed for seed germination. Moisture content was below 13% overall and was not significantly affected by storage technology or storage time. Samples from the polypropylene woven bags suffered significant damage from Sitophilus zeamais and Prostephanus truncatus, with the percentages of insect damage and weight loss reaching 61.4% and 23.4%, respectively. Losses were minimal in seed stored in hermetic containers, with a maximum insect damage of 4.1% and weight loss of 2.2%. Overall, the germination rate of samples stored in these airtight containers was greater than 90%. This study provides additional evidence on the effectiveness of hermetic containers at maintaining Mexican landraces' seed quantity and quality during storage in smallholder conditions in central Mexico.

Ru(ii)/BODIPY core co-encapsulated ratiometric nanotools for intracellular O2 sensing in live cancer cells

Oxygen is a crucial reagent in many biochemical processes within living cells and its concentration can be an effective marker in disease, particularly in cancer where tissue hypoxia has been shown to indicate tumour growth. Probes that can reflect the oxygen concentration and distribution using ratiometric signals can be applied to a range of conventional methods without the need for specialised equipment and are particularly useful. The preparation and in cellulo study of luminescent ratiometric core–shell nanoparticles are presented. Here, a new lipophilic and oxygen-responsive Ru(ii) tris-heteroleptic polypyridyl complex is co-encapsulated with a reference BODIPY dye into the core of poly-l-lysine-coated polystyrene particles. The co-core encapsulation ensures oxygen response but reduces the impact of the environment on both probes. Single wavelength excitation of the particles, suspended in aqueous buffer, at 480 nm, triggers well-resolved dual emission from both dyes with peak maxima at 515 nm and 618 nm. A robust ratiometric oxygen response is observed from water, with a linear dynamic range of 3.6–262 μM which matches well with typical biological ranges. The uptake of RuBDP NPs was found to be cell-line dependent, but in cancerous cell lines, the particles were strongly permeable with late endosomal and partial lysosomal co-staining observed within 3 to 4 hours, eventually leading to extensive staining of the cytoplasm. The co-localisation of the ruthenium and BODIPY emission confirms that the particles remain intact in cellulo with no indication of dye leaching. The ratiometric O₂ sensing response of the particles in cellulo was demonstrated using a plate-based assay and by confocal xyλ scanning of cells exposed to hypoxic conditions.

Uptake and quantitative ratiometric oxygen sensing response of core–shell nanoparticles containing ruthenium probe and BODIPY reference is demonstrated using a plate reader-based assay and by confocal xyλ scanning of live cancer cells under hypoxic conditions.

Use beer to calibrate your CO2 analyser: celebrate!

Bottled beer is used to calibrate a CO₂ analyser by measuring the dilution of O₂ when gas collected in the headspace of the bottle is diluted with atmospheric air. The method is simple and provides an accurate calibration of a CO₂ analyser in the field without the need or hassle of transporting expensive calibration gas.

Biorenewable, transparent, and oxygen/moisture barrier nanocellulose/nanochitin-based coating on polypropylene for food packaging applications

Aluminum-coated polypropylene films are commonly used in food packaging because aluminum is a great gas barrier. However, recycling these films is not economically feasible. In addition, their end-of-life incineration generates harmful alumina-based particulate matter. In this study, coating layers with excellent gas-barrier properties are assembled on polypropylene films through layer-by-layer (LbL) deposition of biorenewable nanocellulose and nanochitin. The coating layers significantly reduce the transmission of oxygen and water vapors, two unfavorable gases for food packaging, through polypropylene films. The oxygen transmission rate of a 60 μm-thick, 20 LbL-coated polypropylene film decreases by approximately a hundredfold, from 1118 to 13.10 cc m^-2 day^-1 owing to the high crystallinity of nanocellulose and nanochitin. Its water vapor transmission rate slightly reduces from 2.43 to 2.13 g m^-2 day^-1. Furthermore, the coated film is highly transparent, unfavorable to bacterial adhesion and thermally recyclable, thus promising for advanced food packaging applications.

Innovations in Smart Packaging Concepts for Food: An Extensive Review

Innovation in food packaging is mainly represented by the development of active and intelligent packing technologies, which offer to deliver safer and high-quality food products. Active packaging refers to the incorporation of active component into the package with the aim of maintaining or extending the product quality and shelf-life. The intelligent systems are able to monitor the condition of packaged food in order to provide information about the quality of the product during transportation and storage. These packaging technologies can also work synergistically to yield a multipurpose food packaging system. This review is a critical and up-dated analysis of the results reported in the literature about this fascinating and growing field of research. Several aspects are considered and organized going from the definitions and the regulations, to the specific functions and the technological aspects regarding the manufacturing technologies, in order to have a complete overlook on the overall topic.

Synthesis of Molybdenum Blue Dispersions Using Ascorbic Acid as Reducing Agent

Stable molybdenum blue nanoparticles dispersions were synthesized using ammonium heptamolybdate and ascorbic acid. The effect of molar ratios of reducing agent/Mo and acid/Mo on the speed of formation and stability of the disperse system has been demonstrated. The particles were characterized by UV/vis, infrared (FTIR), nuclear magnetic resonance (NMR) spectroscopy, and dynamic light scattering (DLS) methods. The X-ray photoelectron spectroscopy (XPS) method confirmed the presence of reduced MoV in the structure of molybdenum oxide nanoclusters, the proportion of which was 30%.

Cellulose Nanocrystal (CNC) Coatings with Controlled Anisotropy as High-Performance Gas Barrier Films

Cellulose nanomaterials are promising materials for the polymer industry due to their abundance and renewability. In packaging applications, these materials may impart enhanced gas barrier performance due to their high crystallinity and polarity. In this work, low barrier to superior gas barrier pristine nanocellulose films were produced using a shear-coating technique to obtain a range of anisotropic films. Induction of anisotropy in a nanocellulose film can control the overall free volume of the system which effectively controls the gas diffusion path; hence, controlled anisotropy results in tunable barrier properties of the nanocellulose films. The highest anisotropy materials showed a maximum of 900-fold oxygen barrier improvement compared to the isotropic arrangement of nanocellulose film. The Bharadwaj model of nanocomposite permeability was modified for pure nanoparticles, and the CNC data were fitted with good agreement. Overall, the oxygen barrier performance of anisotropic nanocellulose films was 97 and 27 times better than traditional barrier materials such as biaxially oriented poly(ethylene terephthalate) (BoPET) and ethylene vinyl alcohol copolymer (EVOH), respectively, and thus could be utilized for oxygen-sensitive packaging applications.

Gas barrier enhancement of uncharged apolar polymeric films by self-assembling stratified nano-composite films

The gas (O₂ and CO₂) permeability of an innovative stratified PE–organoclay (LLDPE/OMMT) nano-enabled composite films was studied for the first time and related to the self-assembly process driven by hydrophobic interactions. An 84.4% and a 70% reduction (i.e. a barrier improvement factor of about 6, sufficient for food packaging applications) were observed respectively in the oxygen and carbon dioxide permeability of the 5 bilayers coated film compared to the substrate, while only incorporating 2.4 v/v% of organoclay in the composite and increasing the thickness by 17.7%. Such drastic effect with so low amount of organoclays cannot be achieved by conventional melt blending/exfoliation of the clays into the polymer matrix and is due to a geometrical blocking effect of a brick-wall and compact layer structure of the impermeable clay tactoids. Mathematical prediction of oxygen barrier performance of PE/OMMT films has revealed that 12 bilayers would be necessary to further achieve a barrier improvement factor of 10.

The gas (O₂ and CO₂) permeability of an innovative stratified PE–organoclay (LLDPE/OMMT) nano-enabled composite films was studied for the first time and related to the self-assembly process driven by hydrophobic interactions.