Biodegradable active coating from chitosan/astaxanthin crosslinked with genipin to improve water resistance, moisture and oxygen barrier and mechanical properties of Kraft paper.

An active chitosan-based coating with an addition of a natural antioxidant and a natural crosslinker has been applied to improve the performance of Kraft paper. Coatings, including chitosan (CS), CS crosslinked with 1.5 % genipin (CS-1.5G), CS containing 1 % astaxanthin (CSA) and CSA crosslinked with 1 % genipin (CSA-1G) were coated on Kraft paper. Uncoated and coated papers were then evaluated for water content (WC), water vapor permeability (WVP), contact angle, oxygen permeability (OP), tensile strength (TS), bursting strength and elongation at break (EAB). Results indicated that the coating improved the properties of Kraft paper. When compared with CS-coated paper, WC and WVP of CSA-1G-coated paper decreased significantly by 40 % and 24 %, respectively. The lowest OP was also observed in CSA-1G-coated paper. CSA- and CSA-1G-coated paper had contact angle values >100°, indicating hydrophobic nature of coated paper surface. All coatings largely improved TS of the paper (by 182-224 %) whereas CS-1.5G and CSA-1G significantly improved the bursting strength of the paper. The developed genipin-crosslinked chitosan-based coating enriched with astaxanthin can improve the functional properties of Kraft paper and thus will facilitate the usage of the paper for food packaging applications.

A key to wine conservation lies in the glass-cork interface.

This study investigates the evolution of the oxygen barrier properties of the bottleneck-stopper system under conditions simulating the conservation of wine in the bottle (presence of model wine, storage position, and temperature) over a long aging period of 24 months. The results highlighted that the oxygen diffusion coefficient of the stopper alone is not modified regardless of the storage conditions. At 20°C, the presence of model wine favors oxygen transfer at the glass-cork interface, accounting for nearly 75% of total oxygen transfer in comparison to cork studied without model wine. Yet, the position of the bottle during storage, vertical (i.e. cork in contact with the vapor phase of the model wine) or horizontal (i.e. cork in contact with the liquid phase), does not influence the oxygen transfer. At higher storage temperatures (35 and 50°C), the barrier properties of the bottleneck-cork system remain stable up to 9 and 3 months, respectively. After this period, an alteration of the barrier properties is observed with an increase of the transfer at the glass-cork interface.

In-situ speciation and estimation of iron(II) and iron(III) contents in anisotropic polysaccharide-based hydrogel by 1H low-field nuclear magnetic resonance.

This article aims to quantify and differentiate in-situ iron(II) and/or iron(III) in heterogeneous polygalacturonate hydrogels using the 1H-NMR relaxometry technique. This holds significant importance, for example, in addressing iron-deficiency anemia through the oral administration of iron(II) supplements. The NMR dispersion profiles of the gels exhibited markedly distinct relaxation behaviors corresponding to the different iron oxidation states. At 20 MHz, two primary relaxation mechanisms must be considered: relaxation arising from water molecules confined within the polygalacturonate fiber mesh and paramagnetic relaxation due to iron cations. When iron(III) serves as the cross-linking agent, paramagnetic interaction dominates the relaxation, while with iron(II) as the cross-linker, both mechanisms have to be considered. To distinguish labile from structuring iron, we monitored the evolution of iron concentrations within the gels during successive washes using NMR and atomic absorption spectroscopy. Eventually, a gel containing both iron(II) and iron(III) was analyzed, and successful differentiation between the two cations was achieved. NMR relaxometry demonstrates powerful capabilities in terms of in-situ experiments, rapid results, speciation (iron(II)/iron(III)), and quantification (labile/ bridging iron).

Effect of a karst system (France) on extended spectrum beta-lactamase (ESBL)-producing Escherichia coli.

Karst aquifers are an important water resource worldwide particularly exposed to anthropogenic pollution, including antibiotic-resistance. The release of antibiotic-resistant bacterial pathogens in the environment is a major public health challenge worldwide. In this One Health study, we aimed to determine the effect of karst on antibiotic-resistant bacteria. For this purpose, we determined the concentrations of extended-spectrum ß-lactamases-producing Escherichia coli (ESBL-Ec) for 92 weeks in a rural karst hydrosystem providing drinking water. ESBL-Ec isolates (n = 130) were sequenced by whole genome sequencing. We analysed the isolates at different levels of granularity, i.e., phylogroup, sequence type, presence of antibiotic-resistance genes, mutations conferring antibiotic-resistance, and virulence genes. The ESBL-Ec concentrations were spatially and temporally heterogeneous in the studied karst hydrosystem. ESBL-Ec isolates survived in the karst and their concentrations were mostly explained by the hydrodynamic of the hydrosystem. We demonstrate that the studied karst has no filtration effect on ESBL-Ec, either quantitatively (i.e., in the ESBL-Ec concentrations) or qualitatively (i.e., in the genetic characteristics of ESBL-Ec isolates).

Development of Smart Bilayer Alginate/Agar Film Containing Anthocyanin and Catechin-Lysozyme.

Smart packaging can provide real-time information about changes in food quality and impart a protective effect to the food product by using active agents. This study aimed to develop a smart bilayer film (alginate/agar) with a cellulose nanosphere (CNs) from corncob. The bilayer films were prepared using 1.5% (w/w) sodium alginate with 0.25% (w/v) butterfly pea extract incorporated (indicator layer) and 2% (w/w) agar containing 0.5% (w/v) catechin−lysozyme (ratio 1:1) (active layer). The CNs were incorporated into the alginate layer at different concentrations (0, 5, 10, 20, and 30% w/w-based film) in order to improve the film's properties. The thickness of smart bilayer film dramatically increased with the increase of CNs concentration. The inclusion of CNs reduced the transparency and elongation at break of the smart bilayer film while increasing its tensile strength (p < 0.05). The integration of CNs did not significantly affect the solubility and water vapor permeability of the smart bilayer film (p > 0.05). The smart bilayer film displayed a blue film with a glossy (without CNs) or matte surface (with CNs). The developed bilayer film shows excellent pH sensitivity, changing color at a wide range of pHs, and has a good response to ammonia and acetic acid gases. The film possesses exceptional antimicrobial and antioxidant activities. The integration of CNs did not influence the antibacterial activity of the film, despite the presence of a higher level of DPPH in film containing CNs. The smart bilayer film was effectively used to monitor shrimp freshness. These findings imply that smart bilayer films with and without CNs facilitate food safety and increase food shelf life by monitoring food quality.

Slow water dynamics in polygalacturonate hydrogels revealed by NMR relaxometry and molecular dynamics simulation.

Diffusions in gels are of prime importance, but their measurements are mainly focused on the diffusion in the pores or through the mesh of the gels. In this study, we performed a deeper dynamic analysis of the water in close interaction with the fibers structuring two heterogeneous polygalacturonate (polyGalA) hydrogels formed by Ca and Zn ions (crosslinking agents). Nuclear magnetic resonance dispersion (NMRD) profiles recorded in-situ by fast-field cycling relaxometry allow to observe the very slow dynamics of water within the gels. Two distinct interpretations of the NMRD profiles are discussed, the first in regard of rotational and translational dynamics in the fibers and the second with respect to a Levy-walk on the fibers' surface. These discussions are confronted with molecular dynamics simulations on a model Ca-polyGalA fiber.

Unraveling the Complex Interfacial Properties of Cork-Based Materials in Their Use as Wine Stoppers.

This study investigates the surface and interfacial properties of the different components of a system composed of an agglomerated cork stopper in a glass bottleneck. Each constituting element has carefully been examined to unveil its underlying complexity. First, there was no effect of supercritical CO2 pretreatment or particle size on the surface properties of cork particles. The wettability of the binder was also evaluated, showing that the binder can spread relatively well on the surface of cork particles. Second, capillary rise measurements carried out on three different agglomerated corks indicate that the formulation of the agglomerates has no effect on its surface properties. The binder represents only a small fraction of the total stopper volume and is therefore not the major contributor to the surface tension. Third, the two coating agents studied display different behaviors. The first one, composed of a paraffin emulsion, exhibits poorer wettability than the second one, composed of a paraffin and silicone emulsion. However, once the coating agent has solidified on the surface of the stopper, both coatings display similar adhesion with the glass of the bottleneck. Starting with fundamental considerations, and then progressing to a more applicative aspect, has led to a better understanding of the properties of cork-based materials in their use as wine stoppers.

Comprehensive approach to the protection and controlled release of extremely oxygen sensitive probiotics using edible polysaccharide-based coatings.

The human intestinal system is a complex of various anaerobes including extremely oxygen-sensitive (EOS) bacteria, some of which have been credited with significant health benefits. Among these, Faecalibacterium prausnitzii, which is one of the most abundant anaerobic bacterial strains in the human intestinal tract, has been proved to be a promising probiotic for the treatment of inflammatory bowel diseases. However, because of its extremely sensitive nature, there are many difficulties when passing through the harsh environment of the gastrointestinal tract. Hence, in this study, a comprehensive physicochemical characterization was performed for the use of polysaccharides from several origins (hydroxypropyl methyl cellulose, methyl cellulose, hydroxypropyl cellulose, chitosan, low-methoxylated pectin, kappa-carrageenan, sodium alginate and pullulan) as encapsulating agents to protect and deliver this bacterium. First, the apparent viscosity and surface tension of the polymer solutions were tested. Then, the mechanical properties, water vapor and oxygen barrier properties of these biopolymers as self-standing films were investigated. Lastly, in vitro release profiles of small molecules and bacterial cells from these biopolymer matrices in contact with a simulated gastrointestinal tract were evaluated. The results showed that chitosan, low-methoxylated pectin, kappa-carrageenan, sodium alginate and pullulan films exhibited good oxygen barrier properties to protect EOS probiotics. Among all the biopolymers tested, sodium alginate exhibited the best oxygen barrier properties and release profile. The release kinetics can be modulated by several factors including biopolymer type, plasticizer concentration and active molecules or bacteria to be encapsulated. On that basis and integrating the other parameters analyzed, a multicriteria strategy for probiotic encapsulation was proposed.

Isolation and Characterization Cellulose Nanosphere from Different Agricultural By-Products.

Cellulose nanospheres (CN) have been considered a leading type of nanomaterial that can be applied as a strengthening material in the production of nanocomposites. This work aimed to isolate and characterize the properties of CN from different agricultural by-products. CNs were successfully isolated from rice straw, corncob, Phulae pineapple leaf and peel using acid hydrolysis (60% H2SO4) combined with homogenization-sonication (homogenized at 12,000 rpm for 6 min and ultrasonicated for 10 min). The results showed that the CN from rice straw (RS-CN) and corncob (CC-CN) exhibited high yields (22.27 and 22.36%) (p < 0.05). All hydrolyzed CNs exhibited a spherical shape with a diameter range of 2 to 127 nm. After acid hydrolysis, Fourier transform infrared (FTIR) results showed no impurities. X-ray diffraction (XRD) showed that the structure of cellulose was changed from cellulose-I to cellulose-II. However, cellulose-I remained in pineapple peel cellulose nanosphere (PP-CN). The crystalline index (CI) ranged from 43.98 to 73.58%, with the highest CI obtained in the CC-CN. The CN from all sources presented excellent thermal stability (above 300 °C). The functional properties, including water absorption Index (WAI), water solubility index (WSI) and swelling capacity were investigated. PP-CN showed the highest WAI and swelling capacity, while the PL-CN had the highest WSI (p < 0.05). Among all samples, CC-CN showed the highest extraction yield, small particle size, high CI, and desirable functional properties to be used as a material for bio-nanocomposites film.

Development of Intelligent Gelatin Films Incorporated with Sappan (Caesalpinia sappan L.) Heartwood Extract.

This study aimed to develop intelligent gelatin films incorporated with sappan (Caesalpinia sappan L.) heartwood extracts (SE) and characterize their properties. The intelligent gelatin film was prepared through a casting method from gelatin (3%, w/v), glycerol (25% w/w, based on gelatin weight), and SE at various concentrations (0, 0.25, 0.50, 0.75, and 1.00%, w/v). The thickness of the developed films ranged from 43 to 63 µm. The lightness and transparency of the films decreased with the increasing concentration of SE (p < 0.05). All concentrations of gelatin films incorporated with SE exhibited great pH sensitivity, as indicated by changes in film color at different pH levels (pH 1−12). Significant decreases in tensile strength were observed at 1.00% SE film (p < 0.05). The addition of SE reduced gelatin films' solubility and water vapor permeability (p < 0.05). The chemical and physical interactions between gelatin and SE affected the absorption peaks in FTIR spectra. SE was affected by increased total phenolic content (TPC) and antioxidant activity of the gelatin film, and the 1.00% SE film showed the highest TPC (15.60 mg GAE/g db.) and antioxidant activity (DPPH: 782.71 µM Trolox/g db. and FRAP: 329.84 mM/g db.). The gelatin films combined with SE could inhibit S. aureus and E. coli, while the inhibition zone was not observed for E. coli; it only affected the film surface area. The result suggested that gelatin films incorporated with SE can be used as an intelligent film for pH indicators and prolong the shelf life of food due to their antioxidant and antimicrobial activities.

Extraction and Characterization of Cellulose from Agricultural By-Products of Chiang Rai Province, Thailand.

Cellulose is an abundant component of the plant biomass in agricultural waste valorization that may be exploited to mitigate the excessive use of synthetic non-biodegradable materials. This work aimed to investigate the cellulose utilized by alkaline extraction with a prior bleaching process from rice straw, corncob, Phulae pineapple leaves, and Phulae pineapple peels. The bleaching and alkaline extraction process was performed using 1.4% acidified sodium chlorite (NaClO2) and 5% potassium hydroxide (KOH) in all the samples. All the samples, without and with the alkaline process, were characterized for their physico-chemical, microstructure, thermal properties and compared to commercial cellulose (COM-C). The extraction yield was the highest in alkaline-extracted cellulose from the corncob (AE-CCC) sample (p < 0.05), compared to the other alkaline-treated samples. The undesired components, including mineral, lignin, and hemicellulose, were lowest in the AE-CCC sample (p < 0.05), compared to raw and alkaline-treated samples. The microstructure displayed the flaky AE-CCC structure that showed a similar visibility in terms of morphology with that of the alkaline-treated pineapple peel cellulose (AE-PPC) and COM-C samples compared to other alkaline-treated samples with a fibrous structure. Fourier Transform Infrared (FTIR) and X-ray Diffraction (XRD) of AE-CCC samples showed the lowest amorphous regions, possibly due to the elimination of hemicellulose and lignin during bleaching and alkaline treatment. The highest crystallinity index obtained in the AE-CCC sample showed a close resemblance with the COM-C sample. Additionally, the AE-CCC sample showed the highest thermal stability, as evidenced by its higher Tonset (334.64 °C), and Tmax (364.67 °C) compared to the COM-C and alkaline-treated samples. Therefore, agricultural wastes after harvesting in the Chiang Rai province of Thailand may be subjected to an alkaline process with a prior bleaching process to yield a higher cellulose content that is free of impurities. Thus, the extracted cellulose could be used as an efficient, eco-friendly, and biodegradable material for packaging applications.

Preparation and Characterization of Bioactive Chitosan Film Loaded with Cashew (Anacardium occidentale) Leaf Extract.

Chitosan is a biopolymer known for its rapid biodegradability and film-forming properties. This research aimed to synthesize and characterize chitosan films loaded with cashew leaf extract (CLE) obtained from immature and mature cashew leaves via aqueous and 70% ethanolic extraction methods. Freeze-dried CLE samples were dissolved in 50% dimethyl sulfoxide for in vitro analysis and chitosan film preparation. The total phenolic content of mature cashew leaves extracted in ethanol (MECLE) showed higher free radicle scavenging activity by a 2,2-diphenyl-1-picrylhydrazyl assay than the other extracts (p < 0.05). MECLE displayed a lower minimal inhibitory concentration, minimum fungal concentration, and higher zone of inhibition against Aspergillus niger compared to the other treatments (p < 0.05). Film-forming solutions were prepared using 2% chitosan, 2% chitosan with 5% mature cashew leaves extracted in deionized water (MACLE) (w/v), and 2% chitosan with 5% MECLE (w/v), respectively, to cast films. Of these, 2% chitosan (CH) with 5% MECLE (CH-MECLE-5) displayed the highest thickness and water vapor transmission rate, water vapor permeability, and oxygen transmission rate when compared to other film samples (p < 0.05). The CH-MECLE-5 film showed the highest inhibition zone of A. niger compared to the control and treated films (p < 0.05). The lightness (L*) of the CH-MECLE-5 film decreased with increment in b* values, which represented the yellow color of the film. In addition, two-photon microscopy revealed a uniform distribution via the auto-fluorescent 3D structure of MECLE in the CH-MECLE-5 film. Therefore, chitosan combined with 5% MECLE may be a potential bioactive and eco-friendly packaging film.

Surface properties of cork: Is cork a hydrophobic material?

Knowledge of the surface tension of cork and its hydrophobicity is of critical importance in many applications of this material at the interface with solid or liquid phases. The conventional technique based on contact angle measurement by sessile drop is not adapted to this naturally textured material and does not allow to accurately determine its hydrophobic character. A study based on capillary rise measurement is reported. A statistical distribution of the surface tension of cork is obtained, based on experiments performed on cork powder with various liquids and using a specific data processing to take into account the intrinsic heterogeneity of cork. This gives a surface tension of 22.6 (±1.2) mN·m-1, with a polar component at 5.2 (±0.5) mN·m-1 and a dispersive component at 17.4 (±1.6) mN·m-1. With a water contact angle of around 90°, cork shows an intermediate hydrophobic/hydrophilic behaviour. Locally, the specific surface texture and chemical composition can reinforce either the hydrophobic or the hydrophilic character. This critical analysis invites reflection on the notion of surface hydrophobicity as it can be determined macroscopically by a contact angle measurement and as defined at the molecular level by the free enthalpy of sorption of water.

Quantification of manganous ions in wine by NMR relaxometry.

Proton relaxation in model and real wines is investigated for the first time by fast field cycling NMR relaxometry. The relaxation mechanism unambiguously originates form proton interaction with paramagnetic ions naturally present in wines. Profiles of a white Chardonnay wine from Burgundy, a red Medoc, and model wines are well reproduced by Solomon-Bloembergen-Morgan equations. Relaxation is primarily governed by interactions with Mn2+. A straightforward model-independent quantification of the manganese ion concentration (down to few tens of µg/L) is proposed.

Four hundred years of cork imaging: New advances in the characterization of the cork structure.

In 1665, Robert Hooke was the first to observe cork cells and their characteristic hexagonal shape, using the first optical microscope, which was invented by him at that time. With the evolution of imaging techniques, the structure of cork has been analysed with greater accuracy over time. This work presents the latest advances in the characterization of this unique material through a multiscale approach. Such investigation brings new insight into the architecture of cork, particularly the differences between the cells of the phellem and those bordering the lenticels. In the latter case, cell differentiation from the lenticular phellogen was restricted to one cell layer, which leads to a cell wall that is 10 times thicker for lenticels. They also displayed a different chemical composition because of unsuberization and a high lignin content in lenticels. Such advances in the knowledge of the structure and composition of cork cells contributes to a better understanding of the macroporosity of cork, down to the nanoscale.

Wine aging: a bottleneck story.

The sporadic oxidation of white wines remains an open question, making wine shelf life a subjective debate. Through a multidisciplinary synoptic approach performed as a remarkable case study on aged bottles of white wine, this work unraveled a yet unexplored route for uncontrolled oxidation. By combining sensory evaluation, chemical and metabolomics analyses of the wine, and investigating oxygen transfer through the bottleneck/stopper, this work elucidates the importance of the glass/cork interface. It shows unambiguously that the transfer of oxygen at the interface between the cork stopper and the glass bottleneck must be considered a potentially significant contributor to oxidation state during the bottle aging, leading to a notable modification of a wine's chemical signature.

Bioactive edible films for food applications:Influence of the bioactive compounds on film structure and properties.

Nowadays, a new generation of edible films is being especially designed for incorporating antimicrobials, antioxidants, enzymes or functional ingredients. Edible films made from natural biopolymers become the focus of many research works as an alternative to synthetic food packaging due to their edibility, biodegradability and compostability as well as to their use as active packaging. Active compounds incorporated in edible films could protect foods against deterioration during storage and therefore extend their shelf life. These active films were mainly studied for the bioactivity, as antimicrobial or antioxidant. However, they could also improve the structure and the physicochemical properties of films through chemical linkage with reactive groups of the polymer chains for instance. Moreover, changing the film structure under cross-linking reaction may increase the cohesion between polymer chains and active compounds, and therefore their retention in the polymer network to better control their release. This manuscript provides an overview on the effect of bio-active compounds incorporation on the film structure and functional properties. Depending on their structure, concentration, reactive groups,.., active compounds can act as plasticizer, but also as anti-plasticizer or cross-linking agents in the biopolymer matrix, and can thus ameliorate the water vapour and gas permeability. Therefore, the retention of bioactive compounds in the polymer network and their release can be better controlled. They can also provide a negative plasticizing effect on the film structure. Hence, the improvement of edible active film functionalities has been investigated to achieve suitable applications on foods.

Bioactive edible films for food applications: mechanisms of antimicrobial and antioxidant activity.

In order to improve the quality of food and to extend their shelf life, a new generation of active edible films is being especially intended after the incorporation of organic acids, enzymes, antimicrobial proteins, phenolic compounds, or other functional ingredients such as probiotics, flavors, vitamins and nutraceuticals. These active compounds have different mechanisms of action related to their structure, their concentration, the nature of micro-organism targeted, the process of encapsulation or incorporation in the biopolymer film-networks. The application of the active films by direct contact or indirect contact via the head space also affects the bioactivity of these compounds. This article critically reviews the published work on active edible-films and their applications for food preservation. The classes of active compounds and their action mechanisms are firstly discussed. Then, an extended overview on their effect on model food (simulants) or on real food during storage was also addressed. Edible films offer two main advantages over the direct incorporation of the antimicrobial or antioxidant agents into the bulk food: 1) to control the diffusion of active compounds at the surface of the food and 2) to reduce the amount of preservatives added in the food.

Impact of functional properties and release kinetics on antioxidant activity of biopolymer active films and coatings.

This work deals with the study of the release kinetics of some natural antioxidants (ferulic acid, caffeic acid and tyrosol) from chitosan-fish gelatin edible films immersed ethanol at 96%, as well as the kinetics of their antioxidant activity using the DPPH assay. The aim was to determine how film functional properties influence the release kinetic and antioxidant activity. The addition of antioxidants to chitosan-fish gelatin matrix decreased the water vapour permeability by more than 30%. The tensile strength (TS) increased up to 50% after the incorporation of antioxidants. Some molecular interactions between polymer chains and antioxidants were confirmed by FTIR where spectra displayed a shift of the amide-III peak. Films containing caffeic acid or a caffeic-ferulic acid mixture exhibited the highest radical scavenging activity, leading to a 90% antioxidant activity at equilibrium but the release rate controlled the efficacy of the system.