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.     

Preparation and properties of thermo-molded bioplastics of glutenin-rich fraction

The present work aims to prepare bioplastics from a glutenin-rich fraction; that is, the gluten residue insoluble in 70% (v/v) ethanol. The influence of reducing agents of sodium bisulfite, sodium sulfite and thioglycolic acid on the properties of the glycerol plasticized doughs and the cross-linked bioplastics were investigated. The results showed that reducing agents can be applied to reduce the Young's modulus of the plasticized dough and to improve the Young's modulus of the cross-linked bioplastics. Moisture absorption, weight loss in water, tensile strength, elongation at break and tensile set were studied to characterize the physical properties of the cross-linked bioplastics.     

Morphology and mechanical properties of thermo-molded bioplastics based on glycerol-plasticized wheat gliadins

Glycerol-plasticized wheat gliadin bioplastics were prepared through thermo-molding method. The effect of glycerol content on the morphology and the mechanical properties of wheat gliadin bioplastics was studied. Morphology, tensile properties (tensile strength and elongation at break), dynamic mechanical properties and rheological properties were evaluated in relation to glycerol content. Experimental results reveal that the morphology, the glass transition temperatures (T_g) of both the gliadin-rich and the glycerol-rich domains and the tensile properties are closely linked to the glycerol content. The time–temperature superposition (TTS) fails to be applied to the dynamic loss modulus G″ (all temperatures) and the dynamic storage modulus G′ (above 80 °C) of wheat gliadin bioplastics.     

Rheological and mechanical properties of bioplastics based on gluten- and glutenin-rich fractions

The present work aims to investigate the dynamic rheology at small strains and the equibiaxial extensional deformation at large strain of the glycerol plasticized dough of gluten- and glutenin-rich fractions and their mixture as well as the uniaxial tension deformation behavior of the compression molded bioplastics. The influence of glutenin-to-gluten ratio (GGR) on the rheological properties of the glycerol plasticized doughs and the crosslinked bioplastics were investigated. The results showed that the glutenin dough exhibits higher moduli and lower loss factor and equibiaxial deformability in comparison with the gluten dough. Addition of a glutenin-rich fraction to the gluten dough can improve elasticity at small deformation and extensional deformational stress at large deformations but result in reductions in extensibility of the compression molded bioplastics.     

Preparation and properties of wheat gluten based bioplastics with fish scale

The objective of this study was to prepare the wheat gluten based bioplastics with fish scale (FS) through compression molding. The tensile strength of the wheat gluten/FS composites (the range of 6.5–7.5 MPa) was higher than that of the neat wheat gluten-based bioplastic (3.40 MPa). There was a good dispersion of the fish scale powder embedded within the wheat gluten matrix. Dynamic mechanical analysis results showed that the tan delta max peak height and storage modulus of the wheat gluten-based bioplasic was reduced by adding the fish scale. Moreover, the addition of the fish scale caused a weight loss and the surface of the wheat gluten based bioplastic after 120 h of accelerated weathering were differed from the neat wheat gluten based bioplastic. These results may help to find a new applications for fish scale waste to control the degradation rate of a wheat gluten based bioplastic in the agricultural field.     

Rheological and mechanical properties of bioplastics based on gluten- and glutenin-rich fractions

The present work aims to investigate the dynamic rheology at small strains and the equibiaxial extensional deformation at large strain of the glycerol plasticized dough of gluten- and glutenin-rich fractions and their mixture as well as the uniaxial tension deformation behavior of the compression molded bioplastics. The influence of glutenin-to-gluten ratio (GGR) on the rheological properties of the glycerol plasticized doughs and the crosslinked bioplastics were investigated. The results showed that the glutenin dough exhibits higher moduli and lower loss factor and equibiaxial deformability in comparison with the gluten dough. Addition of a glutenin-rich fraction to the gluten dough can improve elasticity at small deformation and extensional deformational stress at large deformations but result in reductions in extensibility of the compression molded bioplastics.     

Feather meal-based thermoplastics: Methyl vinyl ether/maleic anhydride copolymer improves material properties

The poultry meat processing industry produces large amounts of feather meal, which is traditionally used as lowvalue plant fertilizer or fish nutrient. A higher value application for feather meal is described in this paper - a thermal blending and compression molding method to create compostable composites out of environmentally friendly materials: feather meal, glycerol, and a biodegradable copolymer of methyl vinyl ether and maleic anhydride (MVEMA). The composite’s mechanical, microstructural and chemical characteristics are described. Feather meal plasticized only with glycerol is mechanically fragile, with average tensile strength of 1.7 MPa, Young’s modulus of 296 MPa and strain-at-failure of 0.6 %. With the addition of MVEMA copolymer, feather meal is transformed into a ductile plastic composite, with tensile modulus reduced 2- to 5-fold and strain-at-failure increased 4- to 25-fold. These properties are ideal for creating feather mealbased compostable bioplastics for agricultural and industrial applications.     

Structure and properties of methylcellulose microfiber reinforced wheat gluten based green composites

Environmentally friendly green composites were prepared by conventional blending wheat gluten (WG) as matrix, methylcellulose (MC) microfibers as filler and glycerol as plasticizer followed by compression molding of the mixture at 127 °C to crosslink the matrix. Morphology, dynamic mechanical analysis (DMA), tensile properties (Young’s modulus E, tensile strength σ_b and elongation at break ?_b), and moisture absorption (MA) and weight loss (WL) in water as well as thermogravimetric analysis (TGA) were evaluated in relation to MC content. It was found that addition of MC microfibers can significantly improve E and σ_b of the composite, which is accompanied by rises in glass transition temperatures of the WG matrix. Influences of MC content on the thermal decomposition and gluten solubility (GS) in water are also discussed.     

The effect of gelation and curing temperatures on mechanical properties of pultruded kenaf fibre reinforced vinyl ester composites

Process parameters such as gelation and curing temperatures are parameters that influence the pultruded kenaf reinforced vinyl ester composites profile quality and performance. The effect of gelation and curing temperatures on mechanical (tensile, flexural and compression properties) and morphological properties of pultruded kenaf reinforced vinyl ester composites were analyzed. Obtained results indicated that increase of gelation and curing temperatures during the pultrusion process of kenaf reinforced vinyl ester composites influenced the mechanical properties of the composites. When the gelation and curing temperatures were increased, tensile strength, tensile modulus, flexural strength, flexural modulus and compressive strength were affected and they were either increased or decreased. The factors that influenced these results include improper curing, excessive curing, water diffusion, and the problems associated with interfacial bonding between fibre and matrices. The optimum values of the tensile strength for gelation and curing temperatures of kenaf pultruded composites were at 100 °C and 140 °C, tensile modulus at 80 °C and 180 °C, flexural strength at 100 ° and 140 °, flexural modulus at 120 ° and 180 °, and compressive strength at 120 °C and 180 °C, respectively. The scanning electron micrographs of tensile fractured samples clearly show that with the increase in gelation temperature, it creates the lumens between matrix and kenaf fibre thus reducing tensile properties whereas increasing the curing temperature caused less fibre pull out and enhanced fibre/matrix interfacial bonding.     

Green composites. I. physical properties of ramie fibers for environment-friendly green composites

The surface topography, tensile properties, and thermal properties of ramie fibers were investigated as reinforcement for fully biodegradable and environmental-friendly ‘green’ composites. SEM micrographs of a longitudinal and cross-sectional view of a single ramie fiber showed a fibrillar structure and rough surface with irregular cross-section, which is considered to provide good interfacial adhesion with polymer resin in composites. An average tensile strength, Young’s modulus, and fracture strain of ramie fibers were measured to be 627 MPa, 31.8 GPa, and 2.7 %, respectively. The specific tensile properties of the ramie fiber calculated per unit density were found to be comparable to those of E-glass fibers. Ramie fibers exhibited good thermal stability after aging up to 160°C with no decrease in tensile strength or Young’s modulus. However, at temperatures higher than 160°C the tensile strength decreased significantly and its fracture behavior was also affected. The moisture content of the ramie fiber was 9.9%. These properties make ramie fibers suitable as reinforcement for ‘green’ composites. Also, the green composites can be fabricated at temperatures up to 160°C without reducing the fiber properties.     

Mechanical characterization of clay reinforced polypropylene nanocomposites at high temperature

This paper focuses on the influence of temperature conditions and the clay contents on enhancement of mechanical characterization of polypropylene (PP) nanocomposites. The nanocomposites were prepared using the melt mixing technique in a co-rotating intermeshing twin screw extruder followed by injection moulding. Nanocomposites properties such as impact strength and ultimate tensile strength, yield strength, failure strain, Young’s modulus and toughness are calculated. The addition of clay to PP matrix was showed remarkable enhancement in mechanical properties at the temperature of 25 oC and 120 °C. Nearly 36 % and 160 % increase in the Young’s modulus and about 45 % and 62 % increase in the impact strength were observed at both room temperature (RT) and high temperature (HT), respectively. But, the tensile strength was not affected much. The basal spacing of clay in the composites was measured by X-ray diffraction (XRD). Scanning electron microscopy (SEM) was used to assess the surface morphology of the fractured surfaces and dispersion of the nanoclay.     

The impact of redox agents on sugar-snap cookie making

The impact of the oxidants potassium bromate and potassium iodate and the reducing agents L-cysteine, glutathione and sodium metabisulfite on sugar-snap cookie making was investigated. Spread behavior of cookie dough during baking (spread rate, set time and collapse) was monitored and texture properties of the baked cookies were determined. Low levels of redox agents impacted neither dough nor cookie properties. High levels of reducing agents (10,000 ppm on a flour base) significantly decreased set time, and, hence, cookie diameter. They also decreased the degree of collapse, which then, evidently, also increased cookie height. Earlier setting and higher resistance to structural collapse, but also the higher intrinsic break strength of the cookie material when adding high levels of reducing agents could be explained on a molecular level as resulting from earlier and more pronounced gliadin–glutenin cross-linking. In contrast, when high levels of oxidizing agents were added, a postponed setting, a more pronounced collapse and decreased intrinsic cookie break strength were observed. The present work demonstrates the importance of heat-induced gluten polymerization during cookie baking and confirms that free sulfhydryl groups are necessary for the polymerization reactions. A model illustrating the role of gluten cross-linking during cookie making is put forward.     

Thermoplastic films from wheat proteins

We show that the wheat proteins gluten, gliadin and glutenin can be compression molded into thermoplastic films with good tensile strength and water stability. Wheat gluten is inexpensive, abundantly available, derived from renewable resource and therefore widely studied for potential thermoplastic applications. However, previous reports on developing thermoplastics from wheat proteins have used high amounts of glycerol (30-40%) and low molding temperature (90-120 °C) resulting in thermoplastics with poor tensile properties and water stability making them unsuitable for most thermoplastic applications. In this research, we have developed thermoplastic films from wheat gluten, gliadin and glutenin using low glycerol concentration (15%) but high molding temperatures (100-150 °C). Our research shows that wheat protein films with good tensile strength (up to 6.7 MPa) and films that were stable in water can be obtained by choosing appropriate compression molding conditions. Among the wheat proteins, wheat gluten has high strength and elongation whereas glutenin with and without starch had high strength and modulus but relatively low elongation. Gliadin imparts good extensibility but decreased the water stability of gluten films. Gliadin films had strength of 2.2 MPa and good elongation of 46% but the films were unstable in water. Although the tensile properties of wheat protein films are inferior compared to synthetic thermoplastic films, the type of wheat proteins and compression molding conditions can be chosen to obtain wheat protein films with properties suitable for various applications.     

Facilitation of α-polylysine in TGase-mediated crosslinking modification for gluten and its effect on properties of gluten films

In this study, α-polylysine was used to enhance the cross-linking effect of TGase on gluten and its effects on properties of gluten films were investigated. The amount of free ammonia released from the cross-linking reaction of gluten induced by TGase at the presence of α-polylysine obviously increased, and more polymers with higher molecular weight were formed from the SDS-PAGE results, which indicated that the TGase-mediated cross-linking reaction ability of gluten was strengthened with the incorporation of α-polylysine. The tensile strength of the films from gluten modified with TGase (20 units/g wheat gluten) and 2% α-polylysine (g/g gluten) for 3 h increased from 4.02 ± 0.09 MPa to 5.28 ± 0.14 MPa, which was more effective than that treated with TGase alone (in which the tensile strength of the films was 4.49 ± 0.10 MPa). The TGase treatment with α-polylysine of gluten improved the water stability of the films much more than that treated with TGase alone. A rougher surface and a more compact cross-section structure were observed by SEM for the films from TGase-α-polylysine treated gluten. The contact angles between the gluten films surface and a water droplet increased because of TGase-mediated cross-linking modification.     

Effects of additives on the rheological and mechanical properties of non-conventional fresh handmade tagliatelle

The effects of the following additives on the amaranth (A), quinoa (Q) and oat (O) dough rheological properties and the extruded tagliatelle dough mechanical characteristics were evaluated: carboxymethylcellulose of sodium (CMC), whey protein isolate (WPI), casein (CAS), chitosan (CHIT) and pregelatinized starch (PS). The amaranth, quinoa and oat rheological dough properties and amaranth, quinoa and oat tagliatelle mechanical characteristics were compared to those of their respective controls (ACTRL, QCTRL and OCTRL) and of the SEMOLINA sample. The storage modulus (G′) and loss modulus (G″) values of the quinoa and oat doughs with PS were similar to those of the semolina dough. For all tagliatelle samples, WPI reduced the elastic modulus or Young's modulus towards that of the semolina tagliatelle. Moreover, the additives did not have particular influence on the tenacity with the exception of the amaranth tagliatelle added with WPI.     

Green composites. II. Environment-friendly, biodegradable composites using ramie fibers and soy protein concentrate (SPC) resin

Fully biodegradable and environment-friendly green composite specimens were made using ramie fibers and soy protein concentrate (SPC) resin. SPC was used as continuous phase resin in green composites. The SPC resin was plasticized with glycerin. Precuring and curing processes for the resin were optimized to obtain required mechanical properties. Unidirectional green composites were prepared by combining 65 % (on weight basis) ramie fibers and SPC resin. The tensile strength and Young’s modulus of these composites were significantly higher compared to those of pure SPC resin. Tensile and flexural properties of the composite in the longitudinal direction were moderate and found to be significantly higher than those of three common wood varieties. In the transverse direction, however, their properties were comparable with those of wood specimens. Scanning electron microscope (SEM) micrographs of the tensile fracture surfaces of the green composite indicated good interfacial bonding between ramie fibers and SPC resin. Theoretical values for tensile strength and Young’s modulus, calculated using simple rule of mixture were higher than the experimentally obtained values. The main reasons for this discrepancy are loss of fiber alignment, voids and fiber compression due to resin shrinking during curing.     

Large deformation stress relaxation and compression-recovery of gluten representing different wheat classes

Despite the great variety of physicochemical and rheological tests available for measuring wheat flour, dough and gluten quality, the US wheat marketing system still relies primarily on wheat kernel hardness and growing season to categorize cultivars. To better understand and differentiate wheat cultivars of the same class, the tensile strength, and stress relaxation behavior of gluten from 15 wheat cultivars was measured and compared to other available physicochemical parameters, including but not limited to protein content, glutenin macropolymer content (GMP) and bread loaf volume. In addition, a novel gluten compression–relaxation (Gluten CORE) instrument was used to measure the degree of elastic recovery of gluten for 15 common US wheat cultivars. Gluten strength ranged from 0.04 to 0.43 N at 500% extension, while the degree of recovery ranged from 5 to 78%. Measuring gluten strength clearly differentiated cultivars within a wheat class; nonetheless it was not a good predictor of baking quality on its own in terms of bread volume. Gluten strength was highly correlated with mixograph mixing times (r = 0.879) and degree of recovery (r = 0.855), suggesting that dough development time was influenced by gluten strength and that the CORE instrument was a suitable alternative to tensile testing, since it is less time intensive and less laborious to use.     

Influence of carboxylic acids on mechanical properties of thermoplastic starch by spray drying

Biodegradable packaging is gaining much attention in food industry as the awareness on sustainability has increased. Thermoplastic starch is a possible alternative. This study evaluated the influence of malic acid (MA) and citric acid (CA), used as a plasticizer, on the mechanical properties of thermoplastic starch (TPS) obtained by spray drying. TPS powder was produced from solution spray drying. This powder was further compression molded to prepare TPS dog-bone test samples. X-ray Diffraction (XRD) results showed that both the spray dried TPS powder and dog-bone test samples were amorphous in nature irrespective of the amount of plasticizer added. Scanning electron microscope (SEM) was used to examine the morphology of solution spray dried TPS powder. No noticeable difference was observed in the morphology. Particles were spherical in shape with homogenous surface. The FT-IR analysis indicated the interaction of plasticizers with starch chains by hydrogen bonding. During TGA analysis, apart from moisture loss at 100 °C, samples were thermally stable up to 170 °C. Mechanical testing of TPS dog-bone revealed that sample containing malic acid as plasticizer exhibited a more elastic behavior as compared to citric acid plasticized formulations. It was revealed that the tensile strength of TPS dog-bone samples was inversely proportional to the quantity of plasticizer used.     

超绿活性茶粉对不同筋度小麦粉面团流变学特性的影响

将超绿活性茶粉(Ultra-green Active Tea Powder,UGA-TP)添加到低筋粉、中筋粉、高筋粉中,加水形成小麦粉面团,利用粉质仪、拉伸仪测定含超绿活性茶粉的不同筋度小麦粉面团流变学特性。研究结果表明:超绿活性茶粉的添加可以提高小麦粉面团吸水率、面团形成时间和面团稳定时间,含茶低筋粉和中筋粉面团与空白面团样品相比,在醒发时间45、90、135 min时,拉伸曲线面积、拉伸阻力、拉伸比例显著增加,延伸度显著下降;其中超绿活性茶粉对低筋粉的影响最大,主要表现为添加超绿活性茶粉后,低筋粉面团吸水率显著增大2.9%,面团形成时间显著增加8.7 min,面团稳定时间显著增加19.2 min;以醒发45 min为例,拉伸曲线面积从76 cm2显著增大到134 cm2,拉伸阻力从300 BU显著增大到645 BU,拉伸比例从2.1显著增大到4.9,延伸度从142显著下降到131。综合得出超绿活性茶粉的添加对不同筋度小麦粉的加工性能均有改善效果,其中对低筋小麦粉改善的效果最大。