Release of coumarin encapsulated in chitosan-gelatin irradiated films

Chitosan and fish gelatin were used to formulate active biobased films containing an antioxidant (coumarin). After drying, the films were irradiated at 40 and 60 kGy using an electron beam accelerator. The effect of irradiation on the film properties as well as the coumarin release mechanism were investigated and compared with the control. Electron Spin Resonance (ESR) revealed free radical formation during irradiation in films containing coumarin. Antioxidant addition and/or irradiation treatment at a dose of 60 kGy resulted in a shift of amide A and amide B peaks. Furthermore a shift of amide II band was only observed for the control film at the same dose. Irradiation allowed improving the thermal stability of the control films. Both irradiation process and addition of coumarin increased the surface wettability (increase of the polar component of the surface tension). From the water barrier analysis, neither irradiation nor coumarin addition influenced the permeability at the lower RH gradient used (0e30% RH). Using the higher RH gradient (30e84%) induced a rise of the WVP of all films (containing or not coumarin) after irradiation treatment. At 60 kGy, the tensile strength of only the control films increased significantly. Considering coumarin release from the film in aqueous medium, the apparent diffusion coefficient of coumarin is two times reduced after irradiation. Irradiation also allowed to better protect the incorporated antioxidant. Indeed, the amount of coumarin in the non-irradiated film was significantly lowered compared to the initial quantity, which is probably due to chemical reactivity

Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.

Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability

Transfert de petites molécules au travers d emballages comestibles appliqués à l interface d aliments composites (de l échelle macroscopique à l échelle moléculaire)

Les transferts de molécules, cause d altération des aliments composites, nécessitent l application en leur sein de couches barrière comestibles au contact entre les différentes phases. La caractérisation, par goniométrie, des propriétés de surface des films, composés de iota-carraghénane et de matière grasse, permet l étude du mouillage et de la pénétration de l eau. La diffusion d une molécule de référence, la fluorescéine, par la méthode FRAP révèle un seuil de teneur en eau critique induisant une augmentation de la mobilité moléculaire et met en évidence le rôle du glycérol, utilisé comme plastifiant. L investigation moléculaire par RMN contribue à identifier les interactions entre polymère et diffusant. Enfin, l analyse par FTIR-ATR donne le coefficient de diffusion de l eau liquide dans le film. Ces travaux d investigations menées à des échelles diverses permettent ainsi de mieux appréhender le mécanisme de perméation dans et/ou au travers des barrières comestibles.Mass transfers of various molecules within multiphasic food products lead to quality deterioration and thus require the use of edible films or coatings in-between the foodstuff. Surface properties characterisation of edible films, composed of a iota-carrageenan matrix in association with a high melting point fat was investigated by goniometry and allows the determination of wetting and water penetration. Diffusion of a reference molecule such as fluorescein by the FRAP method displays a threshold of a critical water content inducing an increase of the molecular mobility, and better explains the role of glycerol, used as plasticizer. NMR molecular investigation contributes to a better understanding and identification of the interactions between the polymer and the diffusant. Finally, FTIR-ATR analysis enables to obtain a diffusion coefficient of liquid water through the film. Such a scaling investigation highlights the permeation mechanism within edible barriers.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Les emballages biodégradables : durée de vie du produit ou durée de vie de l’emballage ? Exemple du PLA

National audienceParmi les matériaux d’emballages issus de ressources renouvelables, il est important de bien différencier ceux qui sont biosourcés mais non biodégradables (souvent analogues aux matériaux conventionnels pétrosourcés) de ceux qui sont à la fois biosourcés et biodégradables. Pour ces derniers, la question de leur stabilité au contact des produits alimentaires s’avère alors cruciale. Le cas du poly(lactide), ou PLA, est détaillé ici, en prenant en compte non seulement sa stabilité chimique, mais aussi sa stabilité physique. Se pose alors la question de la durée de vie de l’emballage en parallèle de celle de la durée de vie de l’aliment emballé

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

International audienceNowadays, 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

Thermoplastic starch and green tea blends with LLDPE films for active packaging of meat and oil-based products

International audienceThermoplastic starch (TPS) is an alternative biomaterial that can be used to produce bioplastics to replace petroleum-based food packaging. Active films were developed from acetylated cassava TPS and green tea using the blown extrusion process. Green tea (GT) and TPS from native starch (NS) and acetylated starch (AS) with different degrees of substitution (DS) were extruded with linear low-density polyethylene (LLDPE) at LLDPE/TPS-GT ratios of 70/30 and 60/40 prior to blown-film extrusion. Results indicated that a higher DS of AS enhanced melt flow index which altered processability and subsequently impacted film microstructures and physical and barrier properties. NS showed highest dispersed particles in film matrices with a lower reduction of mechanical and barrier properties. AS showed reduced surface hydrophobicity with increased water vapor permeability and film solubility due to pore formation. Increased DS of AS films showed enhanced radical scavenging activity (DPPH and FRAP) with improved phenolic release. GT release from the starch matrix effectively limited microbial growth, reduced metmyoglobin forming brown pigment, and stabilized the red color of bacon. Lipid oxidation of packaged soybean oil was effectively reduced by up to 38% depending on the TPS ratio which was attributed to hydrophobicity of the film matrices. Developed TPS-GT films showed high efficacy as active eco-friendlier food packaging, with enhanced stability of meat and oil-based food products

Sorption of 4-ethylphenol and 4-ethylguaiacol by suberin from cork

International audienceCork shows an active role in the sorption of volatile phenols from wine. The sorption properties of 4-ethylphenol and 4-ethylguaiacol phenols in hydro-alcoholic medium placed in contact with suberin extracted from cork were especially investigated. To that purpose, suberin was immersed in model wine solutions containing several concentrations of each phenol and the amount of the compound remaining in the liquid phase was determined by SPME-GC-MS. Sorption isotherms of 4-ethylguaiacol and 4-ethylphenol by suberin followed the Henry's model. The solid/liquid partition coefficients (KSL) between the suberin and the model wine were also determined for several other volatile phenols. Suberin displayed rather high sorption capacity, which was positively correlated to the hydrophobicity of the volatile. Finally, the capacity of suberin to decrease the concentration of 4-ethylphenol and 4-ethylguaiacol was also tested in real wines affected by a Brettanomyces character. It also lead to a significant reduction of their concentration in wine

Effects of acetylated and octenyl-succinated starch on properties and release of green tea compounded starch/LLDPE blend films

International audienceModified starch improved compatibility and modified properties of thermoplastic starch (TPS)/LLDPE blends, producing lower environmental impact food packaging. Effects of modified starch on functional properties and release behavior of green tea (GT) extract compounded with TPS were investigated to produce active film packaging. LLDPE was first extruded with native (NS), acetylated (AS) and octenyl-succinated (OS) starch. The structure of blown-extruded films showed that AS and OS improved compatibility between starch and LLDPE. Modified starch gave better mechanical properties (13-26% and 3-15% for tensile strength and elongation, respectively) and had a more homogeneous structure than NS. Hydrogen bonding between GT and starch modified the compatibility of blend films with surface roughness (9-37%) and greatly increased wettability (3-9%). Surface roughness derived from atomic force microscopy modified wettability in TPS/LLDPE films and controlled release behavior in aqueous media (water, 3% acetic, 10% ethanol and 95% ethanol). High ethanol medium (95% ethanol) accelerated the release rate of GT due to strong affinity of phenolic compounds for the medium and interaction of ethanol with polymer matrices that enhanced diffusion. Barrier properties of blend films were controlled by the hydrophilicity and microstructures of the matrices. AS, OS and GT modified the contraction and crystallization behavior of polyethylene chains as revealed by shifting of infrared adsorption bands and differential scanning calorimetry derived crystallinity, respectively. Modified starch strongly altered the molecular organization of polymers and microstructures and subsequently impacted properties of TPS/LLDPE films

Deposition routes of molecularly imprinted silica for the development of highly specific electrochemical “in-field” sensors

International audienceMolecularly imprinted silica (MIS) electrode coatings have recently returned to the center of scientific research because of their advantages over organic imprinted polymers in electro-chemical analysis. An easy-to-control and well-studied sol-gel process that uses "green solvents", rigid structure and elec-trochemical inertness of the resulting material, applicability of electrochemical deposition techniques are the key elements that make MIS attractive for targeted and sensitive electro-chemical detection. This review aims to draw attention to electrode modification using MIS. It highlights the main stra-tegies for deposing MIS films on the electrode, indicates the adjustments that need to be made to known procedures to achieve an electrochemical sensing system with the best analytical performance, and discusses the advantages and weaknesses of each deposition route

Determination of water intrusion heat in hydrophobic microporous materials by high pressure calorimetry

International audienceThe understanding of interactions between a solid surface and a non-wetting liquid still remains of fundamental interest in numerous research fields, from chemistry to biology. This work focuses on the mechanisms of water intrusion in hydrophobic microporous materials through the thermal analysis of the phenomenon. A specific calorimetric technique coupled to high pressure equipment has been developed to investigate equilibrium thermal effects in such thermodynamic systems from 0 to 400 MPa under isothermal conditions. First validation tests of this method were carried out by compressing degassed water in a constant volume V with successive small pressure increments dp. At equilibrium, the integration of the heat flow as a function of time leads to the differential heat of compression of liquid water δQ/dp from which the thermal isobaric dilatation coefficient of bulk liquid water is calculated. Results show a good balance between experimental and predicted isobaric dilatation coefficients given in literature. Then, the use of this calorimetric device to measure thermal effects of liquid water intrusion in a pure siliceous microporous zeolite, silicalite-1, displays an endothermic effect around 100 MPa, as predicted by other authors using GCMC simulations. The calculation of the intrusion heat, by subtracting the thermal effect of water compression around the porous material, is also validated by comparing microporous versus non-porous silica material. This work opens thus on a powerful method to qualify and quantify mechanical and thermal effects associated with water intrusion in microporous materials under high pressure