Influence of Gelatin-Based Coatings Crosslinked with Phenolic Acids on PLA Film Barrier Properties

Single-use plastics are a major source of pollution and biodegradable polymers could be the best substitute, as they possess similar barrier and functional properties. Aiming at improving barrier properties and providing antioxidant bioactivity, PLA (PolyLactic Acid) films were coated with a crosslinked suspension of plasticized gelatin incorporating phenolic compounds. The coating process induced weak modifications of PLA properties due to plasticization by moisture and glycerol from the coating suspension. Indeed, a double glass transition was displayed. The water vapor barrier properties of the PLA-coated films were not significantly affected. Phenolic compounds induced a crosslinking of the gelatin network, slightly decreasing the moisture sensitivity and surface hydrophilicity. Therefore, the mechanical properties of PLA were maintained after coating and their barrier properties were highly improved, with up to a 600-fold reduction of the oxygen transfer rate. These results make possible new applications for oxidation-sensitive foods, and even for semi-moist foods

Coupling tyrosol, quercetin or ferulic acid and electron beam irradiation to cross-link chitosan–gelatin films: A structure–function approach

International audienceMarine industry by-products, chitosan and fish gelatin, entrapping natural antioxidants (ferulic acid, quercetin and tyrosol) were used to prepare edible active films by casting. The films were composed of chitosan and fish gelatin (1:1 w:w) and incorporating antioxidants (∼50 mg/g). After solvent evaporation (drying), the films were irradiated at 60 kGy by electron beam. This treatment aims at investigating the coupled effect of irradiation with the presence of active compound on the structure and functional properties of the films. Electron Spin Resonance (ESR) unravelled free radical formation during irradiation in films containing ferulic acid or tyrosol which favoured cross-linking between biopolymers. Then, some films became stiffer, the tensile strength increased after the incorporation of antioxidants and/or after irradiation. As expected, as the tensile strength increased, the % of elongation of irradiated and antioxidant-containing films was reduced, except for the irradiated control films. The enhancement of water barrier properties, measured using a 0–30% RH gradient, was observed after ferulic acid and tyrosol additions but remained unchanged after irradiation treatment. A synergic effect of irradiation and active compounds addition was noteworthy on the oxygen barrier properties. Irradiation and antioxidants also induced a slight enhancement of the thermal stability. The surface tension and its dispersive component significantly increased after the incorporation of antioxidants. On the contrary, a significant increase of the polar component is observed for the film containing ferulic acid. Irradiation accentuated the wettability and the hydrophilicity of the film containing quercetin and tyrosol. These results clearly showed that interactions between the polymer chains and/or between the polymer chains and the antioxidants after irradiation were favoured by both antioxidant addition and electron beam treatment. This is confirmed on a molecular scale from the peak shifts observed in amide and carbonyl groups as observed from FTIR

Impact of electron beam irradiation on fish gelatin film properties

International audienceThe objective of this work was to display the effect of electron beam accelerator doses on properties of plasticized fish gelatin film. Electron spin resonance indicates free radical formation during irradiation, which might induce intermolecular cross-linking. Tensile strength for gelatin film significantly increases after irradiation (improved by 30% for 60 kGy). The vapour permeability is weakly affected by irradiation. Surface tension and its polar component increase significantly and are in accordance with the increase of wettability. So, irradiation may change the orientation of polar groups of gelatin at the film surface and crosslink the hydrophobic amino acids. No modification of the crystallinity of the film is observed. These findings suggest that if structure changes, it only occurs in the amorphous phase of the gelatin matrix. It is also observed that irradiation enhances the thermal stability of the gelatin film, by increasing the glass transition temperature and the degradation temperature

Synthesis of polybutadiene-polycaprolactone multi-blokcs based on hydroxyl telechelic polybutadiene. Composition and kinetic study

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Photopolymerizable Synthons from Glycerol Derivatives

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1-n-Butyl-3-methylimidazolium-2-carboxylate: a versatile precatalyst for the ring-opening polymerization of ε-caprolactone and rac-lactide under solvent-free conditions

The ring-opening polymerization of ε-caprolactone (ε-CL) and rac-lactide (rac-LA) under solvent-free conditions and using 1-n-butyl-3-methylimidazolium-2-carboxylate (BMIM-2-CO2) as precatalyst is described. Linear and star-branched polyesters were synthesized by successive use of benzyl alcohol, ethylene glycol, glycerol and pentaerythritol as initiator alcohols, and the products were fully characterized by 1H and 13C{1H} NMR spectroscopy, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). BMIM-2-CO2 acts as an N-heterocyclic carbene precursor, resulting from in situ decarboxylation, either by heating under vacuo (method A) or by addition of NaBPh4 (method B). Possible catalytic and deactivation mechanisms are proposed

New approach for synthesis of poly(ethylglyoxylate) using Maghnite-H + , an Algerian proton exchanged montmorillonite clay, as an eco-catalyst

International audienceIn this works, we have explored a new method for a green synthesis of poly(ethylglyoxylate) (PEtG). This method consists on using a montmorillonite clay called Maghnite-H+ as an eco-catalyst to replace triethylamine which is toxic. Cationic polymerization experiments are performed in bulk conditions at three temperatures (-40 degrees C, 25 degrees C, 80 degrees C) and in THF solutions at room temperature (25 degrees C). At 25 degrees C, an optimum ratio of 5 wt% of catalyst leads to molar masses up to 22000 g/mol in THF solutions. Polymerizations in bulk conditions lead to slightly lower masses than experiments conducted in THF solutions. However, bulk polymerization of ethyleglyoxylate remains a preferable method in order to avoid the use of a solvent and therefore to stay in the context of green chemistry. The structure of obtained polymers are characterized and confirmed by H-1 and C-13 NMR. Thermogravimetric Analysis (TGA) shows an enhanced thermal stability for end-capped PEtG compared to non-terminated PEtG. The best conversion rate (92%) is observed in bulk conditions at 25 degrees C for a reaction time of 48h. An activation energy could be calculated from bulk experiments (Ea = 6.9kJ/mol). An interesting advantage of Maghnite-H+ is an easy recoverage by a simple filtration from the polymer solution

Modeling of the release kinetics of phenolic acids embedded in gelatin/chitosan bioactive-packaging films: Influence of both water activity and viscosity of the food simulant on the film structure and antioxidant activity

International audienceHydrocolloid-based films containing natural phenolic antioxidants (gallic and trans-cinnamic acids at 5% w/wt of polymers) embedded in a gelatin/chitosan matrix were designed as sustainable active packaging. This work deals with characterizing the release mechanisms of the phenolic acids from the films immersed into food simulants (sugar or polyol solutions) having different water activities and viscosities. The films containing gallic acid exhibited higher antioxidant activities than the trans-cinnamic acid films. The use of sucrose or glycerol to reduce the aw both decreases the iron chelating power (antioxidant) and the E Coli growth (antimicrobial). Interactions involved between macromolecules (chitosan and gelatin) and phenolic compounds influence the release kinetic parameters (diffusivity, convection and partition coefficients) that were studied according to the nature of solute, the water activity and the viscosity of the release media. Thermal analysis (TGA and DSC) revealed a plasticization by both sucrose and glycerol, which entered the film

Sorption kinetic of aroma compounds by edible bio-based films from marine-by product macromolecules: Effect of relative humidity conditions

International audienceEdible films based on gelatin and chitosan have high gas and aroma barrier properties. This study focused on their capability to sorbed/retain aroma compounds (1-hexanal, 2-hexen-1-ol, 1-hexanol, 3-hexanone and phenol) at three relative humidity level (≤2%, 53% or 84% RH). Whatever the relative humidity condition, the order of sorption is keton (3-hexanone) < aldehyde (1-hexanal) < aliphatic alcohols (2-hexen-1-ol and 1-hexanol) < phenol. This order could be related to the intrinsic chemical properties of aroma compounds. The increase in moisture enhanced the sorption at the highest RH for all the aroma compounds. However, a competition between water and aliphatic alcohols is observed at 53%RH. All compounds have an ideal sorption behaviour (logarithmic increase) except 1-hexanal. The sorption of 1-hexanal, 1-hexanol, 2-hexen-1-ol and 3-hexanone induced an antiplasticization of the network by increasing the film Tg by more than 5 °C. On the contrary, phenol was an efficient plasticizer at least as high as moisture