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Understanding the origin of the unique rheological properties of wheat gluten, the protein fraction of wheat grain, is crucial in bread-making processes and has raised questions of scientists for decades. Gluten is a complex mixture of two families of proteins, monomeric gliadins and polymeric glutenins. To better understand the respective role of the different classes of proteins in the supramolecular structure of gluten and its link to the material properties, we investigate here concentrated dispersions of gluten proteins in water with a fixed total protein concentration but variable composition in gliadin and glutenin. Linear viscoelasticity measurements show a gradual increase in the viscosity of the samples as the glutenin mass content increases from 7 to 66%. While the gliadin-rich samples are microphase-separated viscous fluids, homogeneous and transparent pre-gel and gels are obtained with the replacement of gliadin by glutenin. To unravel the flow properties of the gluten samples, we perform shear startup experiments at different shear-rates. In accordance with the linear viscoelastic signature, three classes of behavior are evidenced depending on the protein composition. As samples get depleted in gliadin and enriched in glutenin, distinctive features are measured: (i) viscosity undershoot suggesting droplet elongation for microphase-separated dispersions, (ii) stress overshoot and partial structural relaxation for near-critical pre-gels, and (iii) strain hardening and flow instabilities of gels. We discuss the experimental results by analogy with the behavior of model systems, including viscoelastic emulsions, branched polymer melts, and critical gels, and provide a consistent physical picture of the supramolecular features of the three classes of protein dispersions. [ABSTRACT FROM AUTHOR]

Durum wheat gluten proteins are essential for pasta quality. Glutenin polymers undergo solubilization mechanisms during pasta processing. This study aims to investigate gluten proteins insolubilisation kinetics during a resting period applied to extruded. The goal is to investigate the contribution of time related recovery of large glutenin polymers and temperature related formation of glutenin cross-linked aggregates in the pasta quality. Extruded pasta were rested for 120 min at 20, 30 or 40 °C prior drying at high temperature (90 °C). Glutenins insolubilisation induced by resting and drying was assessed from the SE-HPLC elution profiles of the SDS-soluble proteins from fresh, rested and dried pasta. Final pasta were characterized for their organoleptic (color, surface roughness) and physical (diameter, cooking time, viscoelasticity index) properties, before and after cooking. Pasta quality is discussed in relation with the gluten network structure and the impact of resting time. Resting of freshly extruded pasta extrusion leads to spontaneous insolubilisations of glutenins by creation of weak interactions. High temperature drying induces a strong drop of solubility of all gluten protein fractions by creation of covalent bonds, impacting equally rested and not rested pasta. Dry and cooked pasta organoleptic and physical properties are not significantly impacted by a resting time. • Gluten protein insolubilisation upon resting follows a first order kinetics. • High resting temperatures lead to higher levels of protein insolubilisation. • Resting enables covalent bonds creation through SS-SH exchange reactions. • High temperature drying has a higher impact on pasta qualities compared to resting. • Proteins insolubilisation has no significant impact on cooked pasta properties. [ABSTRACT FROM AUTHOR]

Background and objectives: An original experimental approach allowing an unbiased estimate of the impact of three semolina factors (particle size distribution, protein, and ash contents) on durum wheat pasta quality was developed. Findings: By different combinations of the milling fractions from five durum wheat batches displaying contrasted protein levels, 18 blends were obtained covering six levels of protein content (9.2%–13.5%), four levels of ash content (0.66%–1.15%), and three modes of particle size distributions (fine semolina or coarse semolina and mixes of flour and coarse semolina) with distinct median diameter and SPAN. Results showed that dry pasta color was mainly affected by the ash content increase. In addition, dry pasta brightness was also negatively impacted by the protein content. Cooked pasta viscoelastic index was only found positively impacted by semolina protein content but in a nonlinear dose–response relationship and clearly depends on the cooking time. Conclusions: Pasta color can be optimized by managing the milling process to limit the presence of grain outer layers content in semolina, but pasta brightness and cooked pasta viscoelastic index were found specifically related to the protein content. Significance and novelty: The sample set allowed testing the effect of one semolina trait keeping the two other constant and highlighted that beyond a protein content around 12%, no significant gain in pasta viscoelasticity was observed even in case of overcooking. [ABSTRACT FROM AUTHOR]

Major nutritional and agronomical issues relating to maize (Zea mays) grains depend on the vitreousness/hardness of its endosperm. To identify the corresponding molecular and cellular mechanisms, most studies have been conducted on opaque/floury mutants, and recently on Quality Protein Maize, a reversion of an opaque2 mutation by modifier genes. These mutant lines are far from conventional maize crops. Therefore, a dent and a flint inbred line were chosen for analysis of the transcriptome, amino acid, and sugar metabolites of developing central and peripheral endosperm that is, the forthcoming floury and vitreous regions of mature seeds, respectively. The results suggested that the formation of endosperm vitreousness is clearly associated with significant differences in the responses of the endosperm to hypoxia and endoplasmic reticulum stress. This occurs through a coordinated regulation of energy metabolism and storage protein (i.e., zein) biosynthesis during the grain-filling period. Indeed, genes involved in the glycolysis and tricarboxylic acid cycle are up-regulated in the periphery, while genes involved in alanine, sorbitol, and fermentative metabolisms are up-regulated in the endosperm center. This spatial metabolic regulation allows the production of ATP needed for the significant zein synthesis that occurs at the endosperm periphery; this finding agrees with the zein-decreasing gradient previously observed from the sub-aleurone layer to the endosperm center. The massive synthesis of proteins transiting through endoplasmic reticulum elicits the unfolded protein responses, as indicated by the splicing of bZip60 transcription factor. This splicing is relatively higher at the center of the endospermthan at its periphery. The biological responses associated with this developmental stress, which control the starch/protein balance, leading ultimately to the formation of the vitreous and floury regions of mature endosperm, are discussed. [ABSTRACT FROM AUTHOR]

ABSTRACT Glass 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. [ABSTRACT FROM AUTHOR]

The optimal control of processes dealing with non-Newtonian liquids requires the knowledge and control of the power demand of the mixing equipment. In this context, an extension of the Metzner and Otto concept to planetary mixers is proposed to adapt this concept to planetary mixers. The theoretical part of this work defines modified expressions of Reynolds and power numbers. These definitions introduce a characteristic velocity uch that is used to define the parameter Ks. A planetary mixer is employed to experimentally ascertain this guideline. Power consumption measurements carried out by mixing shear-thinning fluids permit to determine the Ks factor. This factor varies only slightly with the flow behavior index and may be regarded as a defined constant for this geometry. Finally, experiments with an additional shear-thickening fluid confirm the validity of this approach. [ABSTRACT FROM AUTHOR]

• RuBisCO is the major protein of LPC extracted from Cichorium endivia leaves. • LPC contains all the essential amino acids in appropriate amount as per AFSSA. • SDS-PAGE reveals RuBisCO large and small chains and a disulphide linked large chain dimer. • LPC is highly soluble (>90%) in aqueous buffers above pH 6. • Minor compounds of LPC affect the physical–chemical properties of RuBisCO. This study provides a detailed characterisation of a leaf protein concentrate (LPC) extracted from Cichorium endivia leaves using a pilot scale process. This concentrate contains 74.1% protein and is mainly composed of Ribulose-1,5-BISphosphate Carboxylase/Oxygenase (RuBisCO). We show that the experimentally determined extinction coefficient (around 5.0 cm−1 g−1 L depending on the pH) and refractive index increment (between 0.27 and 0.39 mL g−1) are higher than the predicted ones (about 1.6 cm−1 g−1 L and 0.19 mL g−1, respectively). In addition, the UV–visible absorption spectra show a maximum at 258 nm. These data suggest the presence of non-protein UV-absorbing species. Chromatographic separation of the concentrate components in denaturing conditions suggests that RuBisCO SC may be covalently bounded to few phenolic compounds. Besides, the solubility of LPC proteins is higher than 90% above pH 6. Such high solubility could make LPC a good candidate as a functional food ingredient. [ABSTRACT FROM AUTHOR]

The 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 ( T g) and in a strong decrease of the rubbery storage modulus, which will favor industrial processing. The increase in T g 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 [ABSTRACT FROM AUTHOR]

The article discusses the findings of a study which characterized the macromolecular structure of various samples of natural rubber (NR) through measurements of Mooney viscosities. The experiment was conducted by a team of researchers from the Cambodian Rubber Institute and the Université Montpellier, France. The research revealed that macromolecular structure of long chain NR samples could not be revealed through the standard Mooney viscosity of 2 revolutions per minute (rpm), while a lower rotor speed enabled more discrimination between samples.

The article reports on the preparation of wheat gluten/montmorillonite films using a thermomechanical process involving the mixing of the components in a two-blade counter-rotating device and then thermoforming the obtained dough. The authors report that protein solubility loss occurred due to the formation and rearrangement of disulfide bonds. They reveal that glycerol had no effect on the films' mechanical properties and water sensitivity. They add that increased thermoforming temperature led to improved mechanical properties.

Grain protein content constitutes a key quality trait for durum wheat end-products and may also impact grain protein composition. A total of sixteen durum wheat cultivars were analyzed in a field trial during two seasons at two nitrogen (N) levels to evaluate whether and to what extent the variation in total grain N was associated with variation in the quantity of the various protein fractions and grain quality parameters. Genotypic variation in grain N content correlated with the variation in the content of all three protein fractions, although the strength of the correlation with gliadin and albumin-globulin was higher than that with glutenins. Genotypic variation in gliadin and glutenin content was more tightly correlated with the variation in the sulfur (S)-rich protein groups than with the S-poor protein groups and subunits. The variation in the percentage of unextractable polymeric proteins (UPP%) among genotypes was independent of their glutenin allelic composition. The significant genotypic differences in UPP% and in the ratios between protein groups and subunits were not influenced by the corresponding variation in grain N content. The final grain N content can only account for part of the variation in quality parameters and in the partitioning of total grain N between protein fractions since genotypic differences other than grain N content also contribute to these variations. [ABSTRACT FROM AUTHOR]

Pasta cooking quality is well known to be related to semolina protein content and composition, however impact of the unextractable polymeric protein content (%UPP) remains disputed. In this work different semolina samples, of variable protein contents (10.5–14.2%) and %UPP (20.2–46.3%) are studied. The changes in %UPP induced by the successive pasta processing steps (mixing, extrusion, drying) but also those occurring during resting periods at 35 °C, applied in-between them, were investigated. Effect of a resting period was moderate after mixing, but pronounced after extrusion. Resting of extruded pasta at 35 °C significantly increased %UPP, which can even grow beyond that of the semolina. No relationship was found between pasta viscoelastic index (VI) and semolina %UPP or protein content. However, cooked pasta VI was found related to the calculated %UPP of rested fresh pasta. [ABSTRACT FROM AUTHOR]

A small bubble-inflation device was developed for use in conjunction with a Low-to-Mid Range Magnification Digital Microscope. This device made it possible to observe the bi-extension of dough and gluten films at the top of a bubble under conditions that mimicked as closely as possible the typical GCW thicknesses, strains, strain rates and gaseous ambience found in dough during everyday proving or baking. For this stage, experiments were carried out at 20 °C. Stress-strain relationships were measured at strain rates ranging from 0.0006 to 0.09 s−1. The reduction in size yielded higher stress measurements compared to the results obtained from usual inflation devices (Alveograph®). Strain hardening in dough and hydrated gluten was observed regardless of the strain rate applied. A first trial using image analysis of the top of the bubble during deformation revealed useful information on the locations of the dough constituents and made it possible to reevaluate strain and strain-rate. The Hencky strain and stress at rupture were found to be of the order of 1.23 and 50–100 kPa respectively. This work illustrates the potential benefits of linking image analysis to a bubble-inflation device for the analysis of the mechanisms involved in the mechanical rupture of dough films. [Display omitted] • A small bubble-inflation device was coupled to a Low-to-Mid Range Magnification Digital Microscope. • The atmosphere composition and temperature around GCW in real dough was mimicked in the device. • Stress-strain was measured at extremely low strain-rate and reevaluated using imaging. • Film constituents were observed during the deformation of thin films (400–700 μ m) until rupture. [ABSTRACT FROM AUTHOR]

Relationships between kernel vitreousness and proteins and starch partitioning to the floury and vitreous regions of the endosperm were monitored in a set of 13 maize inbred lines. Decrease of protein contents from the vitreous to the floury endosperms were mainly assigned to α-zeins. Using Raman microspectroscopy, we observed a protein gradient from the periphery to the center of endosperms that well fitted with the inverse relationships between vitreousness and protein content of the vitreous and floury regions. In addition, Raman microspectroscopy highlighted an increase of starch crystallinity from the periphery to the center of the maize endosperms. This agrees with the higher amylose and associated lipid contents within starches of vitreous than in those of floury endosperms. Finally, starch granules from vitreous regions displayed more channels than the floury ones. These channels contain proteins that might favor adhesion of proteins to starch granules or granule–granule contacts to form the close packing of the vitreous endosperm. Therefore transition from vitreous to floury endosperm is at least the result of both protein and starch gradients. These gradients are probably associated with metabolic gradients that have been observed during endosperm development. [ABSTRACT FROM AUTHOR]

Abstract: Durum wheat is grown in the Mediterranean area where drought and high temperature frequently prevail and impact grain texture, composition and yield. The purpose of this work was to examine the effect of high temperature on grain development and final composition according to the timing of exposure. High temperature (up to 27.5 °C) was applied either during the linear grain filling or drying phases or during whole grain development. The dynamics of grain dry mass, water, glutenin polymers, and protein bodies during grain development were determined. Irrespective of high temperature timing, the arrest of grain filling was observed at 45.9% grain moisture content. At that point, starch granules included in endosperm cells reached their physical packing limit, limiting further deposits. HT applied before physiological maturity shortened the duration of grain filling and resulted in a significant increase in grain protein concentration and in the proportion of vitreous grain. Late formation of sodium dodecyl sulfate (SDS)-insoluble glutenin polymers below 32% grain moisture content was also favored. The ability of wheat storage protein to form a viscoelastic matrix embedding starch granules at the beginning of grain desiccation is proposed to be mandatory for gaining vitreous grains and a high proportion of SDS-insoluble glutenin polymers. [Copyright &y& Elsevier]

Abstract: The effects of drying on pasta structure, starch and protein digestibility and potential allergenicity were investigated. Pasta was dried at low (55°C, LT), high (70°C, HT) and very high temperature (90°C) applied either at the beginning (VHT) or at the end of the drying profile (VHT_LM). Changes in dried and in cooked pasta structure were determined regarding protein solubility, thermal properties of starch, microscopic and rheological measurements. Changes were moderate up to 70°C and increased at higher temperatures and especially for VHT_LM drying. VHT_LM drying tended to decrease starch digestibility and significantly decreased protein digestibility of cooked pasta by 10% probably due to the formation of highly-aggregated proteins linked by very strong covalent bonds. None of the drying profiles were found to remove the allergenic properties of pasta. IgE-reactive peptides from prolamins and albumins/globulins fractions were found in all digestion juices; VHT-LM drying increased the latter. [Copyright &y& Elsevier]