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International audience; This opinion paper offers a scientific view on the current debate of the place of biodegradable plastics as part of the solution to deal with the growing plastic pollution in the world's soil, aquatic, and marine compartments. Based on the current scientific literature, we focus on the current limits to prove plastic biodegradability and to assess the toxicity of commercially used biobased and biodegradable plastics in natural environments. We also discuss the relevance of biodegradable plastics for selected applications with respect to their use and end of life. In particular, we underlined that there is no universal biodegradability of plastics in any ecosystem, that considering the environment as a waste treatment system is not acceptable, and that the use of compostable plastics requires adaptation of existing organic waste collection and treatment channels.

International audience; Polyhydroxybutyrate-co-valerate (PHBV) is a very promising bio-sourced and biodegradable bacterial polyester, the commercial development of which being limited by its high cost. On the other hand, olive oil extraction generates a large amount of lignocellulosic solid residue, called olive pomace (OP), whose disposal raises environmental concerns, including the inhibition of soil microbial populations and the reduction of seed germination. To address these issues, PHBV/OP based biocomposites were produced (at a filler content of 15 wt%) using three different fillers obtained by dry fractionation of OP, i.e. a stone-rich fraction (SF), a pulp-rich fraction (PF) and a crude pomace (F0). The objective of the present work was to investigate how the composition of OP-based fillers influenced the biodegradability of resulting biocomposites. The biodegradation of PHBV, OP-based fillers and OP/PHBV-based biocomposites was assessed by respirometric tests conducted in a standardized soil environment over 4 months. Results showed that the incorporation of OP-based fillers in PHBV favored the overall biodegradability of the materials. Indeed, 100% of biodegradation was achieved after 75, 79 and 87 days for PHBV-F0, PHBV-SF and PHBV-PF formulations respectively, while a biodegradation rate of only 91% was obtained after 123 days in the case of neat PHBV. These results were discussed in the light of several parameters such as the material structure, the affinity of the fillers for the matrix, the composition and the degree of crystallinity of the filler, together with the antibacterial activity of the OP samples assessed by a direct contact technique on solid medium.

International audience; Lignocellulosic by-products are frequently disposed by means of combustion. This study investigates an alternative route for corn cob and Kraft lignin resources in order to support circular economy. The respective plant-based fibres and filler were compounded for the first time together with a poly(lactic acid) (PLA) matrix. Consecutively, seven different biocomposites were processed by injection-moulding and further characterized. The biocomposite containing a mixture of Kraft lignin and corn cob (12 wt% in total) exhibited the highest flexural strength (84 MPa). A proper wetting of PLA onto the corn cob particles demonstrated a good compatibility at matrix/fibre interface. PLA molecular structure changed in presence of 20 wt% lignin filler, with effect on the glass transition temperature and on the composite mechanical strength. The fibres moderately influenced composites surface tension, while Kraft lignin contributed to a slight increase of surface hydrophobicity. Surface energy (σsTotal) of composites have been estimated at 27.6, 28.7 and 27.8 mN/m for PLA/KL-20, PLA/CC-10 and PLA/KL-15/CC-5 respectively. While the polar component (σsPolar) have been estimated at 17.8, 20.0 and 18.7 mN/m for PLA/KL-20, PLA/CC-10 and PLA/KL-15/CC-5 respectively. Unlike the PLA/corn cob composite, those containing Kraft lignin were entirely biodegraded within 2 months in industrial composting conditions study. The materials could be utilized for end-use products thanks to their good mechanical and thermal properties. By adding wood-lignin and corn by-products, materials cost and carbon footprint shall decrease in comparison to pure PLA, while being a biodegradable and sustainable replacement of polyolefins.

International audience

Les comportements humains et l’utilisation intensive du plastique associes a une faible performance des systemes de gestion ont engendre une accumulation massive de dechets plastiques dans le milieu marin ou ils representent 50 a 80 % de l’ensemble des dechets. Leur distribution, leurs comportements en mer, leur degradation et leurs impacts decoulent directement de leur composition et proprietes d’usage. Cette infographie fait un bilan des connaissances et decrit les principaux enjeux scientifiques, environnementaux et socio-economiques, ainsi que les possibles solutions necessaires a la gestion d’un probleme environnemental devenu global.

Human behavior and the intensive use of plastic, combined with poor performance of management systems have led to a massive accumulation of plastic debris in the marine environment, accounting for 50 to 80 % of all marine litter. Their distribution, their fate, their degradation and their impacts stem directly from their composition and use properties. This article reviews knowledge and describes the main scientific, environmental and socio-economic issues, as well as the possible solutions needed to manage an environmental problem that has become global., Les comportements humains et l’utilisation intensive du plastique associés à une faible performance des systèmes de gestion ont engendré une accumulation massive de déchets plastiques dans le milieu marin où ils représentent 50 à 80 % de l’ensemble des déchets. Leur distribution, leurs comportements en mer, leur dégradation et leurs impacts découlent directement de leur composition et propriétés d’usage. Le présent article fait un bilan des connaissances et décrit les principaux enjeux scientifiques, environnementaux et socio-économiques, ainsi que les possibles solutions nécessaires à la gestion d’un problème environnemental devenu global.

Vine shoots are lignocellulosic agricultural residues. In addition to being an interesting source of polyphenols, they can be used as fillers in a poly(3-hydroxybutyrate-3-hydroxyvalerate) (PHBV) matrix to decrease the overall cost and to propose an alternative to non-biodegradable fossil-based materials. The objective of the present work was to investigate how the incorporation of vine shoots fillers and a preliminary polyphenol extraction step could impact the biodegradability of biocomposites. Biocomposites (20 wt %) were produced by microcompounding. The biodegradation of materials was assessed by respirometric tests in soil. The negative impact of polyphenols on the biodegradability of vine shoots was confirmed. This was supported by crystallinity measurements and scanning electron microscopy (SEM) observations, which showed no difference in structure nor morphology between virgin and exhausted vine shoots particles. The incorporation of vine shoots fillers in PHBV slightly accelerated the overall biodegradation kinetics. All the biocomposites produced were considered fully biodegradable according to the French and European standard NF EN 17033, allowing the conclusion that up-cycling vine shoots for the production of lignocellulosic fillers is a promising strategy to provide biodegradable materials in natural conditions. Moreover, in a biorefinery context, polyphenol extraction from vine shoots has the advantage of improving their biodegradability.

The polymer nanocomposites have become unabatedly popular due to their exceptional properties which results in a plethora of applications including the food packaging. However, safety aspect of these materials is still under debate, specifically in view of the unknown interactions of nanoparticles with various additives added during the packages processing. For the commonly used polyolefins, the partitioning of additives rather than their diffusivity dictates the extant and extent of these interactions. In this work, the partitioning of various additives between a clay-polymer nanocomposite (CPN) and several food simulants was measured based on a worst-case scenario in viewpoint of the selected polymer and additives. The added value of the CPN in comparison with the pure polymer (LLDPE) was analyzed with regards to their Hansen solubility parameters and log K-log P linearity. Ultimately, an estimation method based on the Flory-Huggins theory was proposed to predict the partition coefficients in CPN.

International audience; The increase of plastics and microplastics in the environment is a major environmental challenge. Still, little is known about the degradation kinetics of macroplastics into smaller particles, under the joint actions of micro-organisms and physico-chemical factors, like UV or mechanical constraints. In order to gain insight into (bio)-degradation in various media, we perform accelerated erosion experiments by using a well-known enzymatic system. We show that the microstructure of semi-crystalline polymers plays a crucial role in the pattern formation at their surface. For the first time, the release of fragments of micrometric size is evidenced, through a mechanism that does not involve fracture propagation. A geometric erosion model allows a quantitative understanding of erosion rates and surface patterns, and provides a critical heterogeneity size, parting two types of behavior: spherulites either released, or eroded in situ. This new geometric approach could constitute a useful tool to predict the erosion kinetics and micro-particle generation in various media.

International audience; Biodegradable plastics appear as one promising means to help solving the increasing issue of environmental pollution by plastics. The present study aims at comparing the biodegradation mechanisms of two promising biodegradable plastics, PHBV Poly(3hydroxybutyrate-co-3-hydroxyvalerate) and PBSA Poly(butylene succinate-co-adipate) with the objective to provide a better understanding of the mechanisms involved and identify the most relevant indicators to follow biodegradation. For this purpose, the progress of the biodegradation process was monitored under controlled composting conditions at the laboratory scale at 58°C using several methodological approaches for evaluating polymer degradation. Indicators of the extent of material disappearance based on respirometry and

National audience; La pollution des océans par les déchets plastiques est devenue un problème environnemental majeur résultant de son accumulation dans les environnements terrestre et marin. Lorsqu'ils sont mal gérés, les plastiques pénètrent dans le milieu aquatique où ils subissent une dégradation et une fragmentation en microplastiques désormais omniprésents dans tous les milieux aquatiques (Law, 2017). Outre le fait qu'il est impossible d'éliminer les microplastiques du milieu marin, leur impact sur l’environnement est plus important. Diverses études ont montré que de nombreux types d'organismes marins ingéraient des microplastiques, ce qui entraînait des effets néfastes à plusieurs niveaux de la chaîne alimentaire et des écosystèmes marins (Rochman et al., 2016 ; Chae et al., 2017). On soupçonne également que les microplastiques, qui constituent un nouvel habitat pour les micro-organismes, sont des vecteurs de bactéries potentiellement pathogènes (Kirstein et al.,2016 ; Dussud et al.,2018).Le devenir des polymères dans le milieu aquatique dépend à la fois de phénomènes abiotiques (UV, stress mécanique) et biotiques, dus à la colonisation du plastique par des micro-organismes marins (bactéries, phytoplancton, champignons, etc.). Une des principales étapes de la biodégradation est la constitution d'un biofilm et la réduction de la longueur des chaînes de polymère via des exo-enzymes produites par des bactéries issues du biofilm. Une fois que les chaînes de polymère sont suffisamment courtes, elles peuvent être assimilées par les bactéries (Ennouri et al., 2017). Alors que les phénomènes abiotiques entraînent l’endommagement et la fragmentation d’un polymère par des mécanismes d’oxydation et d’hydrolyse, la création de défauts structurels et la propagation de fractures, il est généralement admis que seuls les phénomènes biotiques conduiront à la biodégradation complète d’un polymère, c’est-à-dire à sa conversion en biomasse, eau et CO2. En milieu marin, de nombreuses questions demeurent quant à la cinétique relative de la dégradation abiotique et biotique et à leur impact respectif en termes de fragmentation (Shah et al., 2008). Par exemple, plusieurs articles (Ter Halle et al., 2016 ; Cozar et al., 2018) ont récemment rapporté que la distribution en taille des particules collectées dans l'océan entre 5 mm et quelques centaines de microns ne semble pas correspondre à un processus de fragmentation monocinétique.Les profils d'érosion des polymères semi-cristallins ont fait l'objet d'études approfondies en laboratoire dans des conditions enzymatiques ou bactériennes et divers profils de dégradation ont été observés, leur apparition est principalement liée à la différence de cinétique d'érosion entre les régions cristallines et amorphes (Morse et al., 2011 ; Martinez-Tobon et al., 2018). À ce jour, il y a beaucoup moins d'études sur la manière dont l'évolution des patterns de surface influencera à son tour le processus d'érosion, et pourra conduire à la fracture ou à la génération de fragments.Afin d'étudier le processus d'érosion enzymatique, nous avons utilisé le système bien connu PDLLA / protéinase K (Yamashita et al., 2005). Etant particulièrement intéressés par le rôle des hétérogénéités à l’échelle de quelques nanomètres à quelques micromètres, nous avons utilisé un polymère de composition chimique donnée (PDLLA, 1,7% de D-mer, Mn = 95 kg / mol, indice de polydispersité I = 1,63) et de morphologie contrôlée par traitement thermique.

International audience; Pollution of the ocean by plastic litter has become a major environmental problem resulting from its accumulation in terrestrial and marine environments. When mismanaged, plastics enter the aquatic environment where they undergo degradation and fragmentation into microplastics that are now ubiquitous in all aquatic compartments. In addition to the fact that microplastics are impossible to remove from the marine environment, they are even more damaging than the macro waste. Various studies have shown that microplastics are ingested by many types of marine organisms leading to adverse effects at several levels of the food chain and of the marine ecosystems. It is also suspected that microplastics, that constitute a new habitat for micro-organisms, are vectors for potentially pathogenic bacteria.The fate of polymers in the aquatic environment depends both on abiotic phenomena (UV, mechanical stress), and on biotic ones, due to the colonization of plastics by marine micro-organisms (bacteria, phytoplankton, fungi, etc.). A primary step for bio-degradation is the constitution of a biofilm and reduction of the polymer chain length via exo-enzymes produced by bacteria from the biofilm. Once polymer chains are short enough, they can be assimilated by bacteria. While abiotic phenomena lead to the damage and fragmentation of a polymer by oxidation and hydrolysis mechanisms, creation of structural defects and fracture propagation, it is generally admitted that only biotic phenomena will result into the complete bio-degradation of a polymer, i.e. its conversion into biomass, water and CO2. In the marine environment, many questions remain about the relative kinetics of abiotic and biotic degradation and their respective impact in terms of fragmentation. For instance, several papers have recently reported that the size distribution of particles collected in the ocean between 5mm and a few hundreds of microns, does not seem to correspond to a single-kinetic fragmentation process.The erosion patterns of semi-crystalline polymers have been extensively studied in laboratory under enzymatic or bacterial conditions and various degradation patterns have been observed whose occurrence is mainly linked to the difference in the erosion kinetics between crystalline and amorphous regions. To date, there are much less studies addressing how the evolution of these surface patterns will in turn influence the erosion process, lead to fracture and potential fragments generation.In order to study the enzymatic erosion process, we used the well-known model system PDLLA/proteinase K. Being specifically interested in the role of heterogeneities at the scale of a few nanometers to a few micrometers, we used a polymer of a given chemical composition (PDLLA, 1.7% of D-mer, Mn = 95 kg/mol, polydispersity index I=1.63) and monitored its morphology through its change in crystallinity ratio, everything else remaining constant.Three types of samples were studied: 100% amorphous (A), semi-crystalline with 5% (SC5) and 35% (SC35) crystallinity.The samples morphologies were characterized through DSC, polarized optical microscopy (POM) and SEM. Enzymatic erosion kinetics were measured through weight loss experiments for the 3 polymers and the erosion patterns were observed over time through atomic force microscopy (AFM) and SEM. In order to interpret the results, we combined a simple two-phase geometric erosion model with the well-known Michaelis-Menten model for enzymatic kinetics. Our geometric erosion model is based on the evolution of the erosion front with time induced by the erosion rate difference between crystalline and amorphous regions. This new model accounts very well for the experimental results. Moreover, we observed a morphology-dependent release of fragments, which the model is also able to predict. In particular, one observes the release of spherulites as long as they are smaller than a critical size determined in the model. Some important consequences relevant for the understanding of the formation of micro-plastics in the ocean can be drawn from these experiments.

International audience; Pollution of the ocean by plastic litter has become a major environmental problem resulting from its accumulation in terrestrial and marine environments. When mismanaged, plastics enter the aquatic environment where they undergo degradation and fragmentation into microplastics that are now ubiquitous in all aquatic compartments. In addition to the fact that microplastics are impossible to remove from the marine environment, they are even more damaging than the macroscopic waste.The fate of polymers in the aquatic environment depends both on abiotic phenomena (UV, mechanical stress), and on biotic ones, due to the colonization of plastics by marine micro-organisms. A primary step for bio-degradation is the constitution of a biofilm and reduction of the polymer chain length via exo-enzymes produced by bacteria from the biofilm. Once polymer chains are short enough, they can be assimilated by bacteria. While abiotic phenomena lead to the damage and fragmentation of a polymer by oxidation and hydrolysis mechanisms, creation of structural defects and fracture propagation, it is generally admitted that only biotic phenomena will result into the complete bio-degradation of a polymer, i.e. its conversion into biomass, water and CO2. In the marine environment, many questions remain about the relative kinetics of abiotic and biotic degradation and their respective impact in terms of fragmentation. For instance, several papers have recently reported that the size distribution of particles collected in the ocean between 5mm and a few hundreds of microns, does not seem to correspond to a single-kinetic fragmentation process.In order toWe studiedy the enzymatic erosion process in semi-crystalline polymersand to understand the potential fracture and fragments generation in relation to the formation of erosion patterns in semi-crystalline polymers, we used the well-known model system PDLLA/proteinase K. Being specifically interested in the role of heterogeneities at the scale of a few nanometers to a few micrometers, we used a polymer of a given chemical composition and monitored its morphology through its change in crystallinity ratio, everything else remaining constant. We used the well-known model system PDLLA/proteinase KEnzymatic erosion kinetics were measured through weight loss experiments and erosion patterns were observed over time through atomic force microscopy (AFM) and SEM. In order to interpret the results, we combined a simple two-phase geometric erosion model with the well-known Michaelis-Menten model for enzymatic kinetics. Our geometric erosion model is based on the evolution of the erosion front with time induced by the erosion rate difference between crystalline and amorphous regions. This new model accounts very well for the experimental results and unexpectedly predicts that after a lag time, the final erosion rate will be the one of the fastest eroding phase. Moreover, we observed a morphology-dependent release of fragments, which the model is also able to predict. In particular, one observes the release of spherulites as long as they are smaller than a critical size determined in the model. Some important consequences relevant for the understanding of the formation of micro-plastics in the ocean can be drawn from these resultsexperiments.

Aroma compounds are known to be efficient active agents for a broad range of applications (antimicrobial, anti-oxidant, insect repellent…) that are highly sought when aiming at extending shelf life of food or biological products. However, they are intrinsically odorant and volatile at ambient temperature, which restricts the processing routes used to introduce them in a polymeric matrix and can affect their mode of action and limit efficiency. Indeed, due to their high sensitivity toward temperature they can be lost or transformed during processing. Acting after being released in the headspace, their concentration has to be controlled to avoid any odorant contamination of the targeted products. Hence, the ability for an aroma compound to be retained in a polymeric matrix, and then released when submitted to a triggering effect, are the two main requirements that should be satisfied. The volatile nature of the aroma compound offer the possibility when introduce in the packaging to act by direct or indirect contact with the product and thus to be used in different ways; as a coating layer directly applied on the product surface, as a self-supported film or as coated paper when associated with a paper sheet, as well as an object that could be inserted in the package. As biopolymers such as proteins and polysaccharides are able to retain aroma compounds but also to favor their release by modification of their structure when the relative humidity (RH) and temperature change, they are relevant carriers of these specific aroma compounds. Examples of how active packaging systems with limonene, eugenol and carvacrol as active agents were designed and elaborated. These examples will be presented with a special focus on the processing conditions and the way to improve their aroma compound retention and the release control (biopolymer nature, cyclodextrin clay addition…). Avrami's equation has been used to model the transfer of aroma compound and to advantageously compare it taking into account the mechanism in relation to the biopolymer structural changes.

In this study, the impact of nanofillers on the performance of starch/chitosan composites produced by extrusion was investigated. Blends from three different proportions of starch/chitosan were produced and, for each blend, three different filler concentrations were tested. The natural -Na+ montmorillonite (Mt) and bamboo fibers were used as fillers. The composites were obtained using a twin-screw extruder from homo and nanostructured masterbatch pellets. The films were characterized concerning surface, mechanical, barrier, and thermal properties, as well as morphology and molecular changes. The results showed that the incorporation of Mt or bamboo fibers exhibited high water vapor barrier: films produced from only starch structured with 0.5 g Mt/100 g presented water vapor transmission of (4.9 ± 1.3) g/h m2, whereas films produced from starch/chitosan blend at proportion 75/25 structured with 1.0 g Mt/100 g presented (8.9 ± 0.5) g/h m2. Therefore, these materials showed competitiveness for their application to food packaging.

Polymer nanocomposites and specifically clay-based nanocomposites are emerging in the food packaging area and are promised to have a growing market. While the advantages of the nanoparticles on the gas barrier properties of the nanocomposites are already well-investigated and confirmed, the effect of these nanoparticles on the migration of other non-nano and potentially toxic components of the polymer packaging has still remained unclear. The present study addressed the effect of nanoclay on the migration of various additives from nanoclay/LLDPE nanocomposite packaging by determining the apparent diffusivity of these additives from the samples in contact with four different types of food simulants that distinctively exhibit hydrophilic and lipophilic characters. The results indicated that apart from the tortuosity effect that influence in a low extent the diffusivity of model migrants, the presence of nanoclays modifies the transport properties of materials as a result of their impact on other factors such as crystallinity and swelling capacity. PLS analysis on the influential geometrical and physical properties additionally revealed that the affinity between the food simulant and the polymer has the dominant effect on determining the order of apparent diffusivity as well as the effectiveness of barrier properties of nanoclays to reduce the diffusivity of additives through food packaging. Such statements suggest a benefit provided by nanoparticles incorporation in terms of the human exposure to plastic additives.

Certains materiaux ont la possibilite de subir une decomposition naturelle rapide en etant « consommes » par des bacteries, des champignons, des algues, des insectes, etc. C'est donc une alternative au mode de valorisation par recyclage (et donc de recuperation d'energie). Cet article se propose tout d’abord d’expliciter les etapes de la biodegradation en detaillant les principales reactions, les facteurs impliques ainsi que les methodes de mesure utilisees ; sont ensuite presentes les differents materiaux biodegradables issus de polymeres naturels ou artificiels, et les principales applications industrielles des polymeres biodegradables.

Nanocomposites films were designed from soy protein isolates (SPI), clays (Na+-MMT), and eugenol an antimicrobial agent. Interactions between Na+-MMT and eugenol were evidenced by a shift of the d-spacing by X-ray diffraction analysis. The addition of Na+-MMT (5 and 7.5% w/w) in SPI solution increased its shear thinning behavior and its consistency. Accordingly, a good exfoliation of clays in SPI films was observed. The glass transition temperature of SPI films was impacted by the clays addition but not the water vapor permeability. In contrast, the addition of eugenol in SPI solution did not affected the consistency but induced a decrease of the SPI film Tg and an increase of the water vapor permeability. The presence of eugenol counterbalanced the effect of clays on consistency of film-forming solution. The clay intercalation process was facilitated and the water vapor permeability and active agent release were modified. The presence of clay did not affect the antibacterial effect of eugenol/SPI films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45941.

Current requests in the field of food packaging lead to the reasoned design of materials able to improve the global environmental balance of the food/packaging system by minimizing the negative environmental impact of the packaging material while improving its positive role in the food wastes and losses reduction that strongly impact our environment. This means to simultaneously control food degradation reactions while limiting undesirable migrations of additives from packaging towards in respect of our health and remaining economically competitive. The substitution of oil-based materials by ones issued from renewable and non-food resources (e.g. issued from bioconversion of agro-food wastes, for example) and furthermore, fully biodegradable in natural conditions is also a necessity and represents a significant breakthrough from the research in the field of food packaging. In this context, increasing attention is given to full-biocomposites, i.e. composite materials based on constituents all biosourced and biodegradable. Developing full-biocomposites for food packaging requires taken into account numerous factors, and this is even more important for complex biodegradable materials due to the gap in knowledge on their behaviour and potentialities in usage conditions. The objective of this chapter is to decipher the state of the art on full-biocomposites by considering the specific stakes relative to the food packaging application. After the first part of introduction, the second part will present the role of packaging to ensure food quality and safety and how it should be designed in such a way to reduce food waste and losses. The third part will present the window of mass transfer properties of full-biocomposites, which is the main functional property when considering the food packaging application. The fourth part will consider the economical competitiveness of full-biocomposites, the fifth part will treat the safety issues and the sixth of the different options of end of life and waste management.

International audience; Three black biodegradable films based on PBAT-blends (PBAT/PLA, PBAT/PPC and PBAT/Starch) were tested for vine mulching in real field conditions. The impact of field ageing on their morphology, mechanical performance and ultimate biodegradation was investigated on films exposed at the soil surface or buried into the soil in order to assess the respective contribution of the main related ageing factors i.e. UV radiations and microorganisms. The fact that the soil-facing surface of films exhibited holes 18 months after installation suggested that the biodegradation process could occur above-soil even without previous burying step. However, the early loss of integrity of the biodegradable materials was attributed to UV radiations since beyond a certain threshold the photochemical modifications undergone by the material were too high to sustain its integrity. Whatever the material tested the deterioration of mechanical properties was correlated with the crosslinking of polymer chains inducing the formation of a gel fraction. Considering that the major part of the three materials studied is made of PBAT, the nature of the other polymer constituting the blend would not have a significant impact on the ageing mechanism of the material. Biodegradation analyses conducted in compost medium indicated that field ageing had a low impact on the percentages of mineralization whether the materials had been previously aged or not.

International audience

International audience

BACKGROUND New herbicidal formulations were designed by combining wheat gluten (WG), two montmorillonites (MMTs) (unmodified and organically modified) and a model pesticide (ethofumesate), and their performances were assessed through an integrative study conducted in soil using an experimental methodology with data modelling. RESULTS All the WG formulations tested were effective in decreasing the apparent diffusivity of ethofumesate in soil in comparison with the non-formulated active substance. The slow-release effect was significantly more pronounced in the presence of the organically modified MMT, confirming the importance of sorption mechanisms to reduce ethofumesate diffusion. The bioassays undertaken on watercress to evaluate herbicidal antigerminating performances showed that all the WG formulations (with or without MMT) were more effective than both the commercial formulation and the non-formulated ethofumesate, whatever the concentration tested. To explain such results, it was proposed that WG formulations would enable ethofumesate to be more available and thus more effective in inhibiting seed germination, as they would be less prone to be leached by water transport due to watering and also less subject to photodegradation. CONCLUSION The use of pesticide formulations based on wheat gluten and nanoclays appeared to be a promising strategy both to reduce the mobility of pesticides in soil and to protect UV-photosensitive pesticides from photodegradation.

For the first time, biocomposites from wheat by-products, i.e. wheat gluten and wheat straw fibers, were prepared using a thermomechanical process. Three types of wheat straw fibers displaying contrasted sizes (median diameter d(50) = 1.1 mm, 62 mu m and 8 mu m), morphologies and surface reactivities were prepared by successive grinding processes (cut milling (CM), impact milling (IM) and ball milling (BM), respectively). The main objectives of the present study were (i) to gain further scientific knowledge about the impact of fibers characteristics on the mechanical properties of these composite materials, and (ii) to evaluate in which extent the addition of wheat straw fibers could decrease the final cost of materials without altering their mechanical properties. Mechanical properties were assessed through tensile tests and discussed in relation to the structure of materials, especially to the interfacial adhesion between the fiber and the matrix. Globally, an increasing fiber content up to 11.1 vol% led to an increase in both the Young's modulus and the stress at break, and to a reduction in the strain at break. Experimental Young's moduli were well predicted by the Tsai-Pagano model for the three types of fibers. Data of specific mechanical energy consumed upon processing, contact angle measurements and observations of cryo-fractured surfaces allowed to demonstrate that the adhesion at the interface wheat straw fiber/wheat gluten was improved by (i) an increased hydrophobicity of wheat straw fibers, which was induced by successive grinding, and (ii) a higher specific surface of fibers which was favoured in the case of small fibers. The interfacial adhesion was improved in the order BM > IM > CM whereas the fiber aspect ratio decreased in the order CM > IM > BM. Thus, a competition between these parameters could occur, explaining why no significant difference in reinforcing effect was achieved between the three types of fibers. Finally, the reinforcing effect of wheat straw fibers was also ascribed to a deplasticizing effect, which was particularly pronounced for BM wheat straw fibers. (C) 2012 Elsevier B.V. All rights reserved.

In the aim of resolving environmental key issues such as irreversible soil pollution by non-biodegradable and non-recoverable polyethylene (PE) fragments, a full-scale field experiment was set up to evaluate the suitability of four biodegradable materials based on poly(butylene adipate-co-terephtalate) (PBAT) to be used as sustainable alternatives to PE for mulching application in vineyard. Initial ultimate tensile properties, functional properties during field ageing (water vapour permeability and radiometric properties), biodegradability and agronomical performance of the mulched vines (wood production and fruiting yield) were studied. In spite of their early loss of physical integrity that occurred only five months after vine planting, the four materials satisfied all the requested functional properties and led to agronomic performance as high as polyethylene. In the light of the obtained results, the mulching material lifespan was questioned in the case of long-term perennial crop such as grapevine. Taking into account their mulching efficiency and biodegradability, the four PBAT-based studied materials are proven to constitute suitable alternatives to the excessively resistant PE material. This study has been carried out in the frame of the AGROBIOFILM project with financial support from the European Union 7th Framework Program (FP7/2007–2013) under the grant agreement number 262257.

This study reports the first effort to synthesize a new type of PE–organoclay multilayer film by starting from an uncharged apolar polymer substrate and successively depositing apolar organoclay and uncharged apolar polyethylene (PE) layers with subsequent repeating depositions. The alternate variation of contact angle (85° average for organoclay and 107° for PE layers) confirmed the profilometry and the scanning electron microscopy results as well as the linear growth pattern, i.e. the successful highly stratified assembly of repetitive bilayers comprised of 450 nm organoclays and 2.25 μm PE layers. The self-assembly of organoclays on PE surfaces was driven by solvophobic molecular construction involving hydrophobic interactions between the organic parts of the organoclay tactoids dispersed in an organic solvent and the PE hydrophobic surface. The deposition of PE molecules on the organoclay layers was the result of a dip-coating process involving physical sorption of a highly viscous PE solution on the surface of the organoclay layers.

An organically modified montmorillonite (C30B) was introduced within a wheat gluten (WG)-based formulation containing ethofumesate (as model pesticide) with the aim to enhance its slow release properties by modulating both biodegradation and release properties. For this purpose, biodegradation pattern in soil and release properties in model system have been investigated for ethofumesate alone, WG-ethofumesate and WG-C30B-ethofumesate formulations. Respirometric experiments undertaken with ethofumesate in soil have evidenced a non-biodegradable behavior whereas the incorporation of 0.26% of ethofumesate in WG-based formulation did not affect the final biodegradability of WG-based material in spite of a slight but significant delayed biodegradation pattern. This delaying effect, attributed to the ecotoxic effect of ethofumesate, was shown to disappear when introducing C30B in the formulation. The use of WG-based materials to formulate ethofumesate also resulted in a slow release effect (in water) that could be significantly enhanced by adding organoclays in the materials in spite of a very poor dispersion of the nanoclays within the matrix. Indeed, the presence of clay aggregates evidenced by TEM in the WG matrix would result in the entrapment of ethofumesate taking into account the huge affinity of this pesticide for this nanoclay. This hypothesis appeared fully consistent with the assumption that ethofumesate would be less available to reduce microorganisms respiration and also potentially less subjected to transport mechanisms. As a result, WG-based formulations appeared as a suitable ecofriendly strategy to design slow release delivery system for pesticides with the objective to reduce pesticide leaching in the environment.

E-mail address: c-guillaume@univ-montp2.fr; International audience; The objective of the present work was to understand how the structural, surface, water vapour and gas barrier properties of wheat gluten (WG) coated paper could be influenced by the features of paper. For this purpose, a surface treated paper (TP) and an untreated paper (UTP) were compared. Penetration of WG-coating into the bulk of paper was more pronounced in UTP than TP. This led to the formation of a significant junction zone resulting in an interpenetrated structure for WG–UTP, suggesting a composite- like structure, while a bi-layer one was obtained for WG–TP. Differences in WG penetration were related to the hydrophilicity, roughness and porosity of the paper used. Even though the extent of penetration did not greatly affect the surface properties (water and oil resistance), the transfer properties (water vapour, O2 and CO2) of WG-coated papers were significantly improved when WG-coating highly penetrated: while the WG–TP behaved as a micro-perforated material, the WG–UTP behaved as WG-film

Wheat gluten/montmorillonite (WG/MMT) nanocomposite films were prepared by casting. Transmission electron microscopy observations showed that MMT nanoparticles were homogeneously distributed within the matrix but not completely exfoliated. Contact angles, water uptake and water vapour sorption measurements showed that the presence of MMT led to a significant reduction of the water sensitivity of WG-based materials. This effect was attributed to a different structuring of protein network in the presence of MMT. Significant changes in the permeability of films towards water vapour and aroma compounds were observed for MMT contents higher than 5 wt%, while O2 and CO2 permeabilities remained unchanged. Finally, a slight improvement in tensile properties was obtained for filler contents higher than 2.5 wt%.

Two organic molecules and two inorganic polymers have been used to modify the structure of bentonites as to obtain a high adsorption capacity of thymol, an insecticidal terpenic compound. The selected organic molecules were cetyl and phenyl trimethyl ammonium chlorides (CTMA and PTMA); the inorganic compounds were aluminium hydroxyl and iron hydroxyl polymers. Organic bentonites were obtained after treatment with CTMA and PTMA solutions. Inorganic bentonites were obtained after treatment with polymeric solutions of Alx(OH)y and Fex(OH)y. Materials were characterized by several physicochemical techniques including X-ray diffraction (XRD), thermal gravimetric and differential analysis (TGA, TDA), infrared spectroscopy (FTIR) and nitrogen adsorption–desorption. Adsorption capacities of modified and unmodified bentonites for terpenic compounds were also carried out. Results show that the organic cations have been intercalated successfully into the bentonite interlayer space. XRD measurements show that PTMA and CTMA induce an interlayer space expansion of 4.1 A and 10.5 A, respectively. The increase of specific surface areas (SSA) of materials treated with metallic polycations attests the occurrence of exfoliation. The highest adsorption capacity of thymol is obtained with bentonites modified by alkylammonium, which proves that the modification of the interlayer space is an interesting way to improve adsorption properties of clays usable as support for natural insecticides.

International audience; The modification of sodium montmorillonite after a high pressure pasteurization treatment was followed by X-ray diffraction, FTIR spectroscopy and thermogravimetric analysis. Regardless of the treatment intensity (300 and 800 MPa), the structure of montmorillonite was clearly modified. Such changes should be taken into consideration when binging montmorillonite polymer nanocomposites into contact with food.

An in depth investigation of water transport mechanisms has been undertaken on extruded wheat gluten (WG)/clay materials, which have been shown to display either a nanocomposite or a microcomposite structure depending on the nature of the nanoclay used (i.e. unmodified sodium montmorillonite (named HPS) or organically modified montmorillonite (Cloisite (R) 30B), respectively). The interplay of two concomitant phenomena has been evidenced: first a plasticization of protein chains by water that favors water diffusivity and, second, a clusterization of water as revealed by the Zimm and Lundberg and Guggenheim-Anderson-de Boer theories leading to a slowdown and finally a decrease in water mobility within the polymer. Comparison between liquid and vapor water diffusivity showed a strong impact of the state of the water phase in contact, the water liquid diffusivity being three fold higher than water vapor diffusivity. This Schroeder's paradox could be related to the microporous structure of the extruded wheat gluten materials in which liquid water moves due to an additional capillary phenomenon resulting in a higher apparent diffusivity. As well predicted by the Bharadwaj's tortuosity-based mathematical model, the achievement of a well-exfoliated structure (as observed in the case of the WG-HPS system) has no effect on water diffusivity, whether the phase in contact is liquid or vapor. On the contrary, such a structure led to a significant reduction of the liquid water uptake that might be ascribed to water hydrogen bondings established between the hydrophilic sites of wheat gluten and the unmodified montmorillonite, in turn reducing their availability for water. (C) 2013 Elsevier Ltd. All rights reserved.

Composite materials made from fibrous support coated with agro-polymers are widely commercialized for different appli- cations. But, their transfer properties have only been sparingly studied despite their importance in membrane technologies or food packaging. Furthermore, most of past studies on the topic have been focused on the impact of surface properties of the support on the final coated material structure and its properties; leaving unexplored the potential impact of the in-bulk structure of the support. This study demonstrated the influence of in-bulk structure and especially fibers refining degree of 4 kraft papers (SP28, 36, 60, and 80) on the structure, and surface and gas transfer properties of their respective wheat gluten (WG) coated papers (WGP28, 36, 60, and 80). Paper presenting a high fibers refining degree (SP28) exhibited very tight and narrow in bulk fibers network which pre- vented most of the WG-coated layer penetration, maintaining an important WG apparent layer on top of the paper and a small fibers/wheat gluten composite zone inside (WGP28). Such structure gave strong "WG-like" properties to the final coated material with moderate oxygen permeation and high permselectivity (1.50 3 10 211 mol m 22 s 21 Pa 21 and 8.09, respectively for WGP28) whereas the highly impregnated structure of coated papers built on lowly refined papers (SP80, with wide and loose structure) gave coated materials presenting weak "WG-like" properties, supposedly due to a thick composite zone presenting interfacial defects, with higher oxygen permeation and very limited permselectivity (11.90 3 10 211 mol m 22 s 21 Pa 21 and 1.06, respectively for WGP80). V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2848-2858, 2013

Gas transfer properties of wheat gluten (WG) coated paper and their ability to fulfil the requirements in eMAP of fresh parsley were studied. Permeation of gases through WG-paper was demonstrated to be RH-dependent and closely related to structural modification in the WG layer. Formation of micro-cracks was evidenced in dry conditions; but when increasing RH, plasticisation occurs within the protein layer and micro-fractures were reduced until disappearance. This reversible phenomenon allowed the WG-layer to recover its integrity at RH higher than 70%, and the WG character to be expressed in such conditions. When used at 20 degrees C and 80% RH as part of the packaging of parsley, modified atmosphere was created and a steady state of 11 kPa O-2 and 4.5 kPa CO2 was reached after 45 h. In such conditions, the overall quality of parsley leaves remained acceptable during 8 days, with only 28% loss of chlorophyll. (C) 2013 Elsevier Ltd. All rights reserved.

Specific AFM analytical methods were tested to the surface evaluation of wheat powders at micrometric scale in dry conditions. The objective was to evaluate the adhesion properties of particles based on the main wheat endosperm components (starch, protein, and arabinoxylan) that are characterized by large diversity in terms of chemical composition and particle characteristics. Experiments were conducted by using the force spectroscopy mode to determine interactions generated by the surfaces of particles that were glued on AFM tips, and two reference flat and smooth surfaces, a glass and a polysine slide. Particular care has been devoted to characterize the surfaces in contact since local contact radius is a key parameter in the interpretation of the interactions. The statistical analysis of the normalized adhesion forces have shown the sensitivity of the AFM technique for hydrophobic wheat components and their correlation with the surface tension of the particles.

Nanocomposite films were prepared by a thermo-mechanical process from wheat gluten (WG) and unmodified montmorillonite (MMT). The present work aims at predicting the relationships between the decrease in relative diffusivity of liquid water and the structure of the nanocomposite films, from in situ evaluation of the MMT size aspect ratio and volume fraction, and by using a simple tortuous path mathematical model. The modelling approach first allowed predicting and validating the tortuosity effect of MMT particles on liquid water transport properties of WG-based films. In spite of a well-exfoliated nanocomposite structure, the liquid water diffusivity in WG-based films can at best be decreased by a factor of 2 with this type of clay nanoparticle, which was in agreement with the Bharadwaj model predictions. This study underlines the necessity to achieve a totally exfoliated nanocomposite structure, and above all, to select layered silicates displaying higher size aspect ratio values in order to efficiently improve water barrier properties of WG-based nanocomposite films. Furthermore, the extremely complex structure of nanocomposite materials makes detailed morphological studies often difficult, time and cost consuming. (c) 2012 Elsevier Ltd. All rights reserved.

Sorption properties of clays are effective to control the mobility and availability of pesticides in soil. Adsorption/desorption mechanisms of a model pesticide (ethofumesate) on clays and organoclays were investigated to elucidate the impact of clay structural and chemical properties on clay-pesticide interactions in an aqueous environment. A representative panel of five commercial montmorillonites (MMTs) was studied: a natural sodium MMT, an organically modified montmorillonite (OMMT) with an apolar alkylammonium interlayer cation displaying OH groups and three OMMTs with very apolar alkylammonium interlayer cations. Batch equilibration experiments coupled with Freundlich modeling showed that the amount of adsorbed pesticide and the adsorption/ desorption mechanisms were mainly governed by the polarity and the chemical structure of the MMT interlayer organic cations. The lower the polarity of the MMT, the higher the adsorption capacity. Batch equilibration and batch release experiments both indicated that very little amount of ethofumesate was adsorbed on the edges and external surfaces of all MMTs through hydrogen bonding. For OMMTs, ethofumesate was mainly adsorbed within the gallery by the establishment of stronger hydrophobic interactions with the organic interlayer cation, leading to a rearrangement of alkylammonium chains with a potential basal spacing increase (for high steric hindrance interlayer cations), as confirmed by wide angle X-ray diffraction analysis (WAXS) and Fourier transform infrared spectroscopy (FTIR) analysis. Results provide important advances in the field of sequestration and/or controlled release system of pesticide in soil by using rational strategies of clay chemical modifications, as demonstrated by the slow release properties of organoclay-ethofumesate complexes if compared to commercial formulation pesticide.

The potential use of nanoclays for modulating transfer properties of active agents in bio-sourced polymers was explored. For this purpose, new pesticide formulations were designed by combining wheat gluten, ethofumesate (model pesticide) and three montmorillonites (MMT) using a bi-vis extrusion process. Controlled release properties, evaluated through release experiments in water, were discussed in relation to the material formulations and their resulting structure. Partition coefficients were calculated from experimental data and diffusivity values were identified with a Fick's second law mechanistic model. The effect of temperature on release pattern was also evaluated and the activation energy of diffusion was determined. Ethofumesate release was slowed down for all wheat gluten based-formulations as compared to the commercial product. This slow release effect was increased in the presence of hydrophobic MMTs, due to a higher affinity for ethofumesate than for wheat gluten. Contrarily, hydrophilic MMT, displaying a greater affinity for wheat gluten than for ethofumesate seemed ineffective to slow down its release despite the tortuous pathway achieved through a well-exfoliated structure. To conclude, the release mechanisms would be rather governed by pesticide/MMT interactions than MMT/polymer matrix in the case of a hydrophobic pesticide such as ethofumesate and a hydrophilic matrix such as wheat gluten.

In the current context, protein-based materials might be considered as an alternative to the petroleum-based plastics since fully biodegradable and characterized by remarkable functional properties that can be exploited in a wide range of non-food applications. To improve their performances that are often restricted by high water sensitivity and low mechanical properties, a relevant strategy consisted in the development of protein/clay nanocomposite. For this purpose, several examples of protein-based nano-biocomposites were presented with a special attention for the methods used for the incorporation of layered silicates (organically modified or not) into the matrices and the ultimate functional properties exhibited by the resulting materials. In terms of mechanical properties, the addition of nanoclays leads to a significant improvement of material performance with an increase of Young’s modulus and tensile strength ranging between 1.5 and 2 times. As regards as barrier properties, the improvement appeared quite moderate in spite of a rather good dispersion of layered silicates that would be expected to result in a tortuous pathway limiting diffusion of gases molecules. Thus, a two-fold reduction in water vapour permeability was obtained, and the same or no effect in the case of permeability toward O2 and CO2.

International audience; Wheat gluten coated papers containing carvacrol (15wt%) as anti-microbial agent and montmorillonite (0-7wt%) as filler were investigated as anti-microbial controlled delivery systems. The carvacrol losses were followed during the coating process and storage time at 30 infinity C under controlled RH from 40 to 100% RH. Increasing MMT content limited carvacrol losses during the coating process. A mathematical model based on Fick's second law was used to determine the apparent diffusivities of carvacrol from experimental data of kinetic release at 30 infinity C and controlled RH. Diffusivity values varied from 0.143 x 10(-14) m(2)/s (0wt% MMT, 40% RH) to 6.010 x 10(-14) m(2)/s (5wt% MMT, 100%RH) depending on both MMT% and RH. The carvacrol diffusivities increased with increasing RH, and the presence of a high amount of MMT(>= 5wt%) accentuated the RH-induced effect. Specific aggregated structure was evidenced by SEM and TEM in the presence of carvacrol and 5wt% MMT creating a preferential pathway for carvacrol diffusion. The anti-microbial efficiency of the MMT-WG-coated papers toward Escherichia Coil was assessed and showed that the antimicrobial effect was related to the carvacrol diffusivity. The diffusivity coefficients were utilized to optimize the packaging characteristics required to develop an efficient anti-microbial system and were finally validated against Botrytis cinerea.

Contact: fax: +33 04 6714 4990. E-mail addresses: helene.coussy@univ-montp2.fr, gastaldi@univ-montp2.fr, gontard@univ-montp2.fr, guillard@univ-montp2.fr; International audience; The influence of processing conditions (thermoforming temperature) on water vapour transport properties (permeability, sorption and diffusion) of wheat gluten-based films was studied in relation to structural properties (cross-linking degree of the wheat gluten matrix). Increasing temperature from 80 °C to 120 °C led to a significant decrease in material swelling in high moisture environment and a WVP reduction mainly due to a decrease in diffusivity but without important effect on the moisture sorption isotherms. This was attributed to a higher cross-linking degree of protein network for film thermoformed at 120 °C, with a limited mobility and less possibilities of rearrangement in high moisture conditions.

IATE Axe 2 : Structuration sous contraintes des agropolymères et réactivité des poudres Contacts : fax: þ33 4 6714 4990 ; email adresses : anne.chevillard@univ-montp2.fr, helene.coussy@univ-montp2.fr, cuq@supagro.inra.fr, guillard@univ-montp2.fr, cesar.guy@neuf.fr, gontard@univ-montp2.fr, egastald@univ-montp2.fr; The objective of this work was to investigate the influence of clay nanoparticles on the biodegradability of wheat gluten-based materials through a better understanding of multi-scale relationships between biodegradability, water transfer properties and structure of wheat gluten/clay materials. Wheat gluten/clay (nano)composites materials were prepared via bi-vis extrusion by using an unmodified sodium montmorillonite (MMT) and an organically modified MMT. Respirometric experiments showed that the rate of biodegradation of wheat gluten-based materials could be slowed down by adding unmodified MMT (HPS) without affecting the final biodegradation level whereas the presence of an organically modified MMT (C30B) did not significantly influence the biodegradation pattern. Based on the evaluation of the water sensitivity and a multi-scale characterization of material structure, three hypotheses have been proposed to account for the underlying mechanisms. The molecular/macromolecular affinity between the clay layers and the wheat gluten matrix, i.e. the ability of both components to establish interactions appeared as the key parameter governing the nanostructure, the water sensitivity and, as a result, the overall biodegradation process.

International audience; Protein-based nanocomposites consisting of wheat gluten matrix (WG) and montmorillonite (MMT) modified with quaternary ammonium salts (QA) were developed by hydroalcoholic solvent casting. A simple clay-modifying method using five QA salts of different molecular lengths composed of 4, 5, 16, 40 and 72 carbon atoms, represented by C4N, C5OHN, C16N, C40N and C72N, was used for mineral intercalation. XRD analysis of composites containing Na-MMT, C16N-MMT, C40N-MMT, and C72N-MMT indicated the diffraction peaks corresponding to the interlayer spacing were absent, demonstrating that these particles were significantly dispersed in the WG matrix. Concentration and dispersion of MMT in the WG protein were the main factors affecting on permeability to water vapor P-wv through the films. There was a decrease of P-wv when either the raw or the modified MMT was added. The more prominent decrease of the P-wv was found for dispersed mineral particles, such as C16N-MMT, C40N-MMT, and C72N-MMT

E-mail gastaldi@univ-montp2.fr; International audience; An antimicrobial delivery system was designed from film-forming solutions containing wheat gluten 20% (wt/vol) (WG) as matrix, montmorillonites (Mmt) as structuring agent and carvacrol as active agent (15% wt/wt dry WG). The objectives of this work were to understand how the addition of montmorillonites (0-10% wt/wt dry WG) affects the carvacrol retention capacity of both the film forming solution and the resulting film obtained by casting. For this purpose, structural, granulometric and rheological changes that occurred in the film-forming solutions were studied. The introduction of carvacrol in a WG solution containing increasing amounts of Mmt resulted in dramatic changes in its rheological behaviour. Depending on the Mmt amount added (=5%), the viscosity evolved in different ways indicating an unexpected and specific effect of Mmt on the WG solutions that contain carvacrol. In the presence of a sufficiently high Mmt content (>=5%), particles size measurements and microscopic observations pointed out large aggregated structures. These aggregated structures were supposed to result in an entrapment of carvacrol molecules that could be responsible for a higher carvacrol retention exhibited by both WG film-forming solutions and cast films. Further indications of this assumption were provided by XRD measurements that confirmed the establishment of specific interactions between Mmt, carvacrol and WG. The investigated delivery system based on a WG matrix reinforced by high content of Mmt fillers (>=5%) was clearly efficient to retain and protect an antimicrobial active agent such as carvacrol during the processing stage

J. Appl. Polym. Sci. ISI Document Delivery No.: 229RP Times Cited: 23 Cited Reference Count: 45 Angellier-Coussy, Helene Torres-Giner, Sergio Morel, Marie-Helene Gontard, Nathalie Gastaldi, Ernmanuelle John wiley & sons inc Hoboken; International audience; Wheat gluten (WG)/montmorillonite (MMT) films were prepared by a thermomechanical process consisting of first mixing the components in a two-blade, counter-rotating device and second thermoforming the obtained dough. A significant loss in protein solubility due to the formation and rearrangement of disulfide bonds was observed upon mixing and thermoforming. In the range of studied glycerol contents (25-42.8 wt %), it was shown that glycerol had no significant effect on the mechanical properties or water sensitivity of WG-based films. Increasing the thermoforming temperature from 60 to 120 degrees C led to considerable improvements of the mechanical properties (increases in both the stress and strain at break) and a significant reduction of the water sensitivity. The introduction of MMT (up to 5 wt %) allowed the achievement of mechanical properties that were not possible by just the variation of the glycerol content and the processing temperature.

Wheat gluten (WG), calcium caseinate (CC) and corn gluten meal (CGM), were selected as protein raw material to prepare coating solutions. Different concentrations of protein (10–20%, w/w) and deposited solution layer (50–500 μm) were used to obtain coated papers with thicknesses varying between 143(± 3) and 227(± 8) μm. As expected, the thicknesses of coated paper increased with coating weight, but, for a given coating weight, different thicknesses were observed according to the raw material used and its concentration in the coating solution. A phenomenon involving a penetration of coating solution inside paper was suspected with WG-based solutions. The microstructure of coated papers was analyzed by SEM, OM and AFM and differences in structure and morphology were observed between the three raw materials. The percentages of coating agent impregnated inside paper were also calculated from the apparent density of coated paper and the density of self-supported films prepared in the same conditions but deposited on an inert and smooth Plexiglas® support. These percentages of impregnation ranged from 4.8 to 63.3% and increased as following: CC