Plasticized Wheat Gluten Research Articles

Bio-on presents method to convert waste oils into biopolymer raw material

Edible films based on plasticized wheat gluten protein were prepared by intensive mixing followed by compression molding. The effects of water and glycerol, which were selected as plasticizers for the wheat gluten, as well as the processing conditions (mixing time and molding temperature) on the physical and mechanical properties of the films were evaluated. The resulting films were characterized in terms of moisture sorption, total soluble matter, water vapor permeability, dynamic mechanical and tensile properties. It was found that plasticizer type and concentration had a dominating effect on mechanical properties and WVP, while other physical properties remain almost non-affected. Moreover, the effect of the added plasticizer (glycerol) on the film properties strongly depends on natural presence of water in commercial gluten (9% as is). On the other hand, the pressing temperature affected the final properties of the films more than the mixing time because the former influences the final cross-linking degree of the protein network. Processing temperatures higher than 100 °C led to darker films that would be discarded by consumers if they were used as food packaging.

Effect of filler load and high-energy ball milling process on properties of plasticized wheat gluten/olive pomace biocomposite

The increase of particles surface area can optimize the dispersion state of biocomposite components and enhance their properties. First in this paper, we aimed to elaborate a novel biocomposite without any treatments. Plasticized wheat gluten (WG), was filled with 0–20% of olive pomace (OP) powder. The second objective was the improvement of biocomposite properties using physical treatment. High-energy ball milling process was applied on the blend of wheat gluten and olive pomace powders (MPs). The grinding effect of particle shape, size and distribution in biocomposite was characterised by particle size distribution using a laser-light diffraction and by SEM analysis. The cryo-fractured surface of selected films, mechanical properties, moisture absorption and thermal properties of both biocomposites were described in details. It was found that the sensitivity of biocomposites to moisture absorption was reduced with the increase of filler content after the applying of high-energy ball milling process. The thermal stability of OP biocomposite decreased with the increase of loading, while that of MPs was unaffected by high-energy ball milling process. This process affects the physical and morphological characteristics of the powders. The mechanical properties were improved by grinding process at filler content lower than15%.

Dynamic mechanical analysis of the multiple glass transitions of plasticized wheat gluten biopolymer

ABSTRACTGlass transition of thermo‐molded biomaterials made from wheat gluten and its main protein classes is studied by dynamic mechanical analysis (DMA). The materials are plasticized with variable contents of glycerol (30–40 wt %) and water (0–20 wt %). For all materials, three successive relaxation phases are systematically detected. Their positions shift to lower temperature as the plasticizer content of materials increases. Composition in gluten, glycerol and water of each relaxation phase is estimated using the Couchman‐Karasz model. Irrespective of the plasticizer content or composition, the relaxation phases shows rather constant plasticizer volume fractions. The low‐, middle‐, and high relaxation phases include respectively around 30, 60 and 80 vol % of gluten protein. These relaxations are assigned to the segmental motion of the surface amino‐acid side groups, to the collective motion of packed gluten proteins, and to the gain in protein conformational mobility as a 2D network of interacting plasticizer molecules forms. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43254.

Three-Layer Films Based on Wheat Gluten and Electrospun PHA

Because no known pure biopolymer exhibits all the desired physicochemical properties required for every conceivable packaging application, multilayer films are here proposed as an alternative to improve the performance of protein-based films. In this work, three-layer films based on plasticized wheat gluten films have been developed by applying a more hydrophobic electrospun polyhydroxyalkanoate layers on both sides of the protein film. A commercial polyhydroxybutyrate (PHB) and a polyhydroxybutyrate-co-valerate copolymer with 3 % valerate content (PHBV3) have been used. The morphology, oxygen and water vapour barriers, the optical properties as well as the mechanical performance have been characterized. The effect of film processing temperature (145 and 160 °C) and the amount of electrospun material constituting the outer layers played an important role on the final physicochemical properties of these films. The results showed that water vapour barrier properties were mainly governed, on the one hand, by the deposited amount of the electrospun PHB layer and, on the other hand, by the temperature used for PHBV3-WG-PHBV3 assembly. However, oxygen permeability was greatly influenced by the type and amount of the polyhydroxyalkanoates (PHAs) instead of the temperature used. The lowest water vapour permeability (WVP) and oxygen permeability (OP) values were obtained for three-layer films prepared with 1 mg PHBV3·cm−2 and processed at 160 °C, reaching values of 3.14 ± 0.2 e−11 kg·m·Pa−1·s−1·m−2 and 4.36 ± 0.05 e−15 m3·m·m−2·s−1·Pa−1, respectively. The addition of PHB or PHBV3 outer layers improved the mechanical properties (especially Young’s modulus, which increased up to ~40 % for the three-layer films containing thicker layers) of plasticized wheat gluten films. However, the transparency of the three-layer films was slightly affected by the processing temperature and by the thickness of the outer layer.

Preparation of plasticized wheat gluten/olive pomace powder biocomposite: Effect of powder content and chemical modifications

Abstract During the last decades, a lot of interest was given to the biocomposites development, due to the low cost and degradability of waste food industries. In this study, biocomposites were developed from Wheat Gluten plasticized by 35% of glycerol, containing 0–20% of Clean Olive Pomace (COP), Esterified Clean Olive Pomace (ECOP), or Mercerized Clean Olive Pomace (MCOP) powders, which were prepared by conventional blending. Chemical modifications of the powders were characterized by Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and thermogravimetric analysis (TGA). Mechanical properties, water absorption, mass loss and thermal properties of biocomposites were detailed. It was found that thermal stability of powder was improved after mercerization. Incorporation of COP powder (20%) in plasticized wheat gluten (WG) improved significantly Young's modulus compared to that of WG films. Water absorption was decreased significantly at 20% of reinforcement and was 29% less than that of WG films. Young's modulus and tensile strength decreased at 5% of ECOP powder, contrary to MCOP biocomposite Elongation at break of biocomposites was decreased with increasing powder content. Incorporation of COP powder (20%) decreased thermal stability of the biocomposite, nevertheless chemical changes did not affect the thermal stability of the ECOP and MCOP biocomposites.

Wheat gluten films obtained by compression molding

Edible films based on plasticized wheat gluten protein were prepared by intensive mixing followed by compression molding. The effects of water and glycerol, which were selected as plasticizers for the wheat gluten, as well as the processing conditions (mixing time and molding temperature) on the physical and mechanical properties of the films were evaluated. The resulting films were characterized in terms of moisture sorption, total soluble matter, water vapor permeability, dynamic mechanical and tensile properties. It was found that plasticizer type and concentration had a dominating effect on mechanical properties and WVP, while other physical properties remain almost non-affected. Moreover, the effect of the added plasticizer (glycerol) on the film properties strongly depends on natural presence of water in commercial gluten (9% as is). On the other hand, the pressing temperature affected the final properties of the films more than the mixing time because the former influences the final cross-linking degree of the protein network. Processing temperatures higher than 100 °C led to darker films that would be discarded by consumers if they were used as food packaging.

Nanostructural morphology of plasticized wheat gluten and modified potato starch composites: relationship to mechanical and barrier properties.

In the present study, we were able to produce composites of wheat gluten (WG) protein and a novel genetically modified potato starch (MPS) with attractive mechanical and gas barrier properties using extrusion. Characterization of the MPS revealed an altered chain length distribution of the amylopectin fraction and slightly increased amylose content compared to wild type potato starch. WG and MPS of different ratios plasticized with either glycerol or glycerol and water were extruded at 110 and 130 °C. The nanomorphology of the composites showed the MPS having semicrystalline structure of a characteristic lamellar arrangement with an approximately 100 Å period observed by small-angle X-ray scattering and a B-type crystal structure observed by wide-angle X-ray scattering analysis. WG has a structure resembling the hexagonal macromolecular arrangement as reported previously in WG films. A larger amount of β-sheets was observed in the samples 70/30 and 30/70 WG-MPS processed at 130 °C with 45% glycerol. Highly polymerized WG protein was found in the samples processed at 130 °C versus 110 °C. Also, greater amounts of WG protein in the blend resulted in greater extensibility (110 °C) and a decrease in both E-modulus and maximum stress at 110 and 130 °C, respectively. Under ambient conditions the WG-MPS composite (70/30) with 45% glycerol showed excellent gas barrier properties to be further explored in multilayer film packaging applications.

Preparation and properties of rice husk‐filled plasticized wheat gluten biocomposites

Rice husk (RH) reinforced wheat gluten/glycerol (Gly/Glut) and rice husk (R) reinforced wheat gluten‐glycerol/chitosan‐polyethylene glycol (Gly/Glut‐CP) biocomposites with varying rice husk loading were prepared. Morphological, thermal, and mechanical properties of the biocomposites were investigated by scanning electron microscope, thermogravimetric analyzer, and tensile testing machine, respectively. Water absorption properties and surface functional groups of the biocomposite films were determined by weight measurement and attentuated total reflectance Fourier transform infrared spectroscopy, respectively. The results were discussed in terms of chitosan‐polyethylene glycol (CP) and rice husk content. Although CP and 1‐g rice husk addition decreased maximum degradation temperature of Gly/Glut film, adding of more rice husk did not considerably change the maximum degradation temperature. As a result of adding CP, the tensile strength of Gly/Glut film was increased by about 183%, whereas tensile modulus was decreased by about 34%. POLYM. ENG. SCI., 54:1477–1483, 2014. © 2013 Society of Plastics Engineers

Extrusion Processing of Wheat Gluten Bioplastic: Effect of the Addition of Kraft Lignin

Plasticized wheat gluten (WG) was extruded with 0-50 wt% Kraft lignin (KL) contents using a co- rotating twin screw extruder with circular die. The objec- tive of this study was to evaluate the effect of KL on the extrusion processing, and on the resulting properties of those new materials. The addition of either 30 or 50 wt% KL which is a radical scavenger allowed increasing the extrusion die temperature from 80 to 110 C. Moreover, the addition of 10-50 wt% KL contents improved the processability of WG in extrusion: it decreased both die pressure and residence time for all studied feed rates and screw speeds. The addition of KL induced a protein depolymerization and the association between KL and WG as evidenced by the co-elution of KL and WG in SE- HPLC. Moreover, the addition of 10-30 wt% KL improved mechanical properties and reduced the water absorption of WG-based material.

Improving wheat gluten materials properties by Kraft lignin addition

AbstractThe industrial production of wheat gluten (WG)‐based biomaterials implies to improve their actual mechanical properties as well as to reduce their water sensitivity. In this study, the effect of Kraft lignin (KL) content on the processability and on the physical properties of WG materials was investigated. WG plasticized with glycerol was blended with KL, and processed into materials by mixing and thermomolding. Materials were characterized by dynamic mechanical thermal analysis, tensile test, and water absorption measurements. The introduction of KL in plasticized WG resulted in an increase of the material glass transition temperature (Tg) and in a strong decrease of the rubbery storage modulus, which will favor industrial processing. The increase in Tg did not follow a simple mixing rule, demonstrating specific interaction between KL and WG. The resulting materials effectively showed improved properties when compared with pure WG‐based materials: they exhibited higher tensile strength and lower water sensitivity in ambient conditions. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Wheat gluten-based renewable and biodegradable polymer materials with enhanced hydrophobicity by using epoxidized soybean oil as a modifier

Epoxidized soybean oil (ESO) was applied as an additive for wheat gluten (WG) to modify the properties of the renewable and biodegradable natural polymer materials. Optimum intermolecular interactions and crosslinking between ESO chains and the WG matrix were achieved under alkaline conditions. The WGESO materials were heterogeneous on a scale of 20–30 nm, but the homogeneity was improved upon increasing the amount of glycerol as a plasticizer in the materials. The combination of plasticization and crosslinking effects derived from ESO resulted in good retention in mechanical strength for the plasticized WGESO materials as compared to those without 10 wt % of mobile ESO additives. The hydrophobicity of the plasticized WG materials was also enhanced significantly by using the ESO additives.

Plasticized wheat gluten reinforcement with natural fibers: Effect of thermal treatment on the fiber/matrix adhesion

Wheat gluten-based materials reinforced with hemp fiber were prepared at different thermomolding temperature, and their mechanical properties were characterized. Reinforcement, calculated as the ratio between the composite Young’s modulus and the matrix Young’s modulus was shown to decrease when the thermomolding temperature increased from 100 to 130 °C. However, the feature cannot be explained neither by a matrix deplasticization nor a variation in the extent of gluten cross-linking. The effect of the thermomolding temperature on the pressure sensitive adhesives properties of gluten-based matrix was evaluated by the measurement of their rheological properties (elastic and viscous modulus) at various frequencies. Results confirmed that the better adhesives properties were obtained at lower temperature, suggesting that this parameter affects the reinforcement.

Influence of reducing agents on properties of thermo-molded wheat gluten bioplastics

The present work aims to study the influence of reducing agents of sodium bisulfite, sodium sulfite and thioglycolic acid on the equibiaxial extensional deformation of glycerol plasticized wheat gluten and the properties of gluten bioplastics thermo-molded at 125 °C. Moisture absorption, weight loss and water uptake, uniaxial tensile properties (Young's modulus, tensile strength, elongation at break and tensile set), and morphology observations were performed to characterize the physical properties of the thermo-molded gluten bioplastics. The results showed that reducing agents facilitated the viscous flow and restrained the elastic recovery of the plasticized gluten while not hindering the crosslinking reaction of gluten proteins during thermo-molding. On the contrary, reducing agents do not significantly influence moisture absorption, Young's modulus, tensile strength and the morphology of the gluten bioplastics thermo-molded at 125 °C. It is shown that reducing agents are highly effective for tailoring the flow viscosity of the plasticized gluten dough and the mechanical properties of thermo-molded gluten bioplastics.

Reinforcement of plasticized wheat gluten with natural fibers: From mechanical improvement to deplasticizing effect

Wheat gluten/glycerol-based materials were reinforced through natural fiber addition. Hemp and wood fiber addition increased both composite tensile strength and Young’s modulus, but decreased elongation at break. Resulting materials exhibited lower water sensitivity. Fiber addition does not modify the protein aggregation, but resulted in an increase of the composite matrix glass transition temperature (Tg). This increase was attributed to the plasticizer migration from the matrix to the fibers, which increased the matrix Young’s modulus. This migration called matrix deplasticization contributed to the improvement of the overall composite mechanical properties. The true reinforcing effect attributed to the fiber addition and the deplasticizing effect attributed to plasticizer migration were dissociated and quantified. At high fiber content, deplasticizing effect became significant and reduced material processability. This study suggested that the fiber lignin content is susceptible to influence both the water sensitivity and the matrix deplasticization. 2008 Elsevier Ltd. All rights reserved.

Bulk plastic materials obtained from processing raw powders of renewable natural polymers via back pressure equal channel angular consolidation (BP-ECAC)

Renewable natural polymers wheat starch (WS) and wheat gluten (WG) were successfully processed into plastic bulk materials using back pressure equal channel angular consolidation (BP-ECAC) without using any additional plasticizers at relatively low temperatures. The strong shear deformation occurred during the process caused an effective deformation of WS or WG granular structures and resulted in an efficient gelatinization of starch or plasticization of gluten with the natural moisture content. Sufficient chain entanglement was formed in both WS and WG materials for achieving strong cohesion among the macromolecule matrixes. The mechanical strength of the obtained plastic materials was comparable to that of conventional polymers but stronger than the strength of thermoplastic WS or plasticized WG. The processing temperature played an important role in determination of morphologies and properties of the plastic materials. Increasing processing temperature would cause more effective gelatinization or plasticization of the natural polymers, enhance the interactions among different components in the systems, and form materials with improved mechanical properties. Thermal cross-linking might play a positive role in the improvement of mechanical properties when processing temperature was increased. However, thermal decomposition could also occur under such severe shearing especially at high temperatures. The optimum temperature for conducting such process was around 100–120°C for WS and WG. The BP-ECAC method provides a potential to manufacture natural polymer based plastic materials efficiently on an industrial scale for various applications.

Chemical Modification of Wheat-Protein-Based Natural Polymers: Formation of Polymer Networks with Alkoxysilanes To Modify Molecular Motions and Enhance the Material Performance

The mechanical performance of plasticized wheat gluten (WG) materials was significantly modified through the formation of different chemical and network structures with alkoxysilanes. The epoxy-functionalized alkoxysilanes were grafted to segments of WG, and then the condensation reactions between alkoxysilane segments occurred during thermal processing to form WG-siloxane networks. The mechanical properties and molecular motions of the networks were dependent on the amount and type of alkoxysilanes applied. A lower amount of alkoxysilanes caused the alkoxysilane molecules to predominately graft onto WG chains without forming linkages between WG segments, which produced an additional plasticizing effect on the WG systems with a longer elongation value and weaker tensile strength at relative humidity (RH) = 50% as compared to the WG system. However, such grafting improved the hydrostability of the materials and generated an improvement in tensile strength at RH = 85%. Increasing the amount of alkoxysilanes in the systems led to the formation of cross-linked WG-siloxane networks via linkages between alkoxysilane segments. Remarkable strength improvement was obtained for the networks with elongation values still higher than the original plasticized WG due to the flexible nature of the siloxane components. A more significant strength improvement was obtained for the WG-SiA systems at both RH = 50% and 85%, where SiA could form three-dimensional networks from siloxane condensation and generate highly cross-linked network structures with relatively low mobility. For WG-SiB systems, SiB could only form linear linkages, and the higher mobility of the SiB phase caused the systems to display a lower strength improvement with a longer elongation value.

Network formation in glycerol plasticized wheat gluten as viewed by extensional deformation and stress relaxation: Final conclusions

The aim of the present work has been to study the influence of rest time on the structural development of gluten/glycerol mixtures with gluten volume fraction ranging from 0.56 to 0.75 by equibiaxial and uniaxial deformations at room temperature. The Gaussian and the Mooney–Rivlin relations are used to evaluate shear moduli at small and medium strains and the Kohlrausch–Williams–Watts (KWW) model is used to analysis relaxation modulus at biaxial strain 0.7. Shear moduli and average relaxation time are discussed in relation to gluten content for the mixtures with a rest time of 150 min and also to a mixture of 0.61 gluten volume fraction with different rest times.

Wheat-Gluten-Based Natural Polymer Nanoparticle Composites

A series of wheat-gluten-based nanocomposites were produced by dispersing Cloisite-30B nanoclay particles into plasticized wheat gluten systems under thermal processing conditions. The exfoliation of the nanoparticles as confirmed by wide-angle X-ray diffraction and transmission electron microscopy has resulted in significant enhancement of the mechanical properties for both deamidated proteins and vital gluten systems under 50% relative humidity (RH). Such strength improvement was also pronounced for wheat gluten (WG) systems under a high humidity condition (RH = 85%). A similar level of further strength enhancement was obtained for the WG systems that had been strengthened by blending with poly(vinyl alcohol) (PVA) and cross-linking with glyoxal. Although the nanoclay modifier, a quaternary ammonium, caused an additional plasticization to the materials, the interactions between the gluten matrix and the nanoparticles were predominant in all of these nanocomposites. A solid-state NMR study indicated that the polymer matrix in all of these nanocomposites displayed a wide distribution of chain mobilities at a molecular level (less than 1 nm). The interactions between the nanoparticles and the natural polymer matrix resulted in motional restriction for all components in the mobile phases including lipid, plasticizers, and plasticized components, although no significant influence from the nanoparticles was obtained in the mobility of the rigid phases (unplasticized components). On a scale of 20-30 nm, the deamidated protein systems tended to be homogeneous. The small domain size of the matrix resulted in modifications of the spin-lattice relaxation of these systems via spin diffusion. The residual starch seemed to remain in a relatively larger domain size in WG systems. The nanoparticles could enhance the miscibility between the starch and the other components in the WG nanocomposite, but such miscibility enhancement did not occur in the WG/PVA blend and the cross-linked system. These polymer matrixes were still heterogeneous on a scale of 20-30 nm.

Equibiaxial extensional deformation and stress relaxation of glycerol plasticized wheat gluten at different concentrations

The aim of the present work has been to study the equibiaxial extensional deformation of glycerol plasticized moisture-containing gluten (MG) with different MG volume fractions ranging from 0.56 to 0.75 under lubricated squeezing flow at room temperature. The hyperelastic model with a strain energy potential of the Mooney–Rivlin form is applied to describe the biaxial stress as a function of biaxial strain at low strains. The initial shear modulus as a function of MG volume fraction reveals a particle network of gluten. Analysis of the relaxation modulus at biaxial strain 0.7 on the basis of the Kohlrausch–Williams–Watts (KWW) model reveals that decreasing volume fraction of MG increases the width of the distribution of relaxation times as well as the average relaxation time of wheat proteins.

The phase composition and molecular motions of plasticized wheat gluten-based biodegradable polymer materials studied by solid-state NMR spectroscopy

The water plasticized wheat gluten (WG) materials were prepared by thermal processing and studied by dynamic mechanical analysis and solid-state NMR spectroscopy. The results indicate that the materials displayed a broad distribution of molecular motions and could be divided into different phases in terms of their mobility above the Tg. The rigid phase mainly consisted of proteins and starch with enhanced interactions between the two components via hydrogen bonding with water molecules. Lipid and water formed the mobile phase, however, lipid molecules were always more mobile than water. The intermediate phase consisted of plasticized starch and proteins (mainly proline and glutamine segments). The whole plasticized WG materials were heterogeneous at a scale of 20–30nm, but the miscibility between proteins and starch was enhanced via increasing hydrogen bonding interactions with water molecules. Such strong hydrogen bonding acted as adhesion among these multi-components/phases over a wide range of temperature thus resulting in good mechanical properties of the materials. The results demonstrated that solid-state NMR techniques can provide valuable information of quantitative composition of phase structures with different mobility in a multi-component system and the chemical nature of each phase along with the interactions among these components/phases.