Ultrastructure of Consecutively Extracted and Flocculated Gliadins and Glutenins

Gliadin and glutenin are characterized by specific ultrastructures, which depend on variety and separation conditions. Gliadins, extracted with 80% ethanol, of Israeli spring wheat ‘Ariel’ appeared as spherical bodies within an amorphous perforated matrix. The gliadins of a commercial sample of U.S. hard red winter wheat were deposited in bundles of bodies of concentric membrane-like units during water dialysis and they tended to separate while heating at 120 °C. Acetic-acid-extracted glutenins heated at 120 °C appeared as amorphous compact agglomerated particles beside dispersed aggregates, fibril-like patterns and oil-like bodies. The extracted glutenins, which were dialysed vs water, appeared as dispersed or aggregated particles beside oil-like bodies embedded in and/or encapsulated by coagulated protein. Differences were found in high-performance capillary electrophoresis patterns of both gliadins and glutenins between the Israeli spring wheat ‘Ariel’ and the good baking quality U.S. hard red winter wheat ‘Karl 92’; indicating that the structural differences are a result of different proteins and differences in the physicochemical properties of the proteins.     

Stability of wheat proteins in solution

Gluten from defatted wheat flour was used to study the stability of protein extracts during various steps that are routinely made in protein analyses. These included aqueous extraction and short-term storage, handling of chromatographic fractions, freeze-drying and reconstitution. Protein composition was monitored by size-exclusion high performance liquid chromatography (SE-HPLC) and sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Distilled, deionized and sterilized water were used to prepare the gluten solutions (TFA or HCl solutions at pH 3.0) and to prepare elution solvents. In distilled or deionized water there was a decrease of polymeric protein and a corresponding increase in the monomeric components with time unless initial heating was applied. Protein extracts obtained from gluten and solvents prepared with freshly sterilized water showed no change during storage for 4 days at a temperature of 25 °C. Microbiological assays of the water samples supported the view that microbial contaminants were the source of proteases. After elution from SE-HPLC column with acetonitrile/water followed by freeze-drying and re-dissolution, the SE-HPLC profile of the monomeric proteins was unchanged. However, polymeric proteins aggregated, lost solubility and showed an altered SE-HPLC profile. The effect appeared to be due to the presence of acetonitrile and could be avoided by membrane concentration instead of freeze-drying.     

Distribution and function of LMW glutenins,HMW glutenins,and gliadins in wheat doughs analyzed with ‘in situ’ detection and quantitative imaging techniques

The different gluten subunits, gliadins, LMW glutenins, and HMW glutenins have been reported to play different key roles in different type of wheat products. This paper studied the interaction between gliadin, LMW and HMW glutenins in soft, hard and durum semolina flour doughs during different stages of mixing. In order to see how do the gluten subunits (gliadin, LMW glutenin and HMW glutenin) redistribute during mixing, dough samples were taken at maximum strength and 10 min after maximum strength. The doughs have been mixed with the same level of added water (55%), therefore they all have different strengths values due to their changes in proteins content. Oscillatory rheological measurements were performed on the doughs. It has been found that HMW glutenins are relatively immobile because of their less molecular mobility and do no redistribute themselves especially at high strength for doughs such as hard wheat flour. LMW glutenins and gliadins on the other hand redistribute themselves at even at high dough strengths forming a more stable network. In weaker doughs such as soft wheat, the breakdown of the three proteins subunits is responsible for the decay in dough strength. We have also visualized how the greater amount of LMW glutenins in semolina is in constant interaction with HMW glutenins and gliadins allowing the dough to maintain a stable strength for an extended mixing time. Finally, we have found the ‘in situ’ detection and quantitative analysis techniques to be more sensitive to the changes occurring in the gluten network of the dough than the oscillatory rheological analysis.     

Effect of heat on rheology of gluten fractions from flours with different bread-making quality

Flours from wheat varieties of differing bread-making quality were fractionated using a sequential salt precipitation technique. The gluten fractions in the different varieties varied in the proportion of HMW, LMW glutenins and gliadins. Their rheological behaviour was examined using constant strain (2%) small deformation oscillation tests over frequencies ranging from 0.005 to 10 Hz, before and after heating at 90 °C. The fractions containing a higher proportion of HMW glutenins were associated with a predominantly elastic character, whereas fractions containing mostly gliadins exhibited a viscous-like behaviour. The frequency dependent rheological behaviour of fractions containing HMW proteins was less susceptible to heat, and their elastic character was maintained after heating, whereas the rheology of intermediate fractions and fractions containing mostly gliadins was more susceptible to heating, indicating a rapid change from viscous to elastic behaviour after heating.     

Heat Coagulation of Wheat Flour Albumins and Globulins,their Structure and Temperature Fractionation

Albumins and globulins were fractionated by coagulation at 70, 100, and 120°C and were studied by microscopic and electrophoretic methods. The coagulated albumins of a U.S. commercial hard red winter (HRW) wheat blend sample included larger aggregates than those of an Israeli spring wheat (SW). Dialyzed globulins appeared as finger-like patterns with embedded oil droplets and heat-coagulated globulins appeared as aggregates with fibril-like patterns. An increase in size of coagulated aggregates was observed as temperatures increased (70, 100, and 120°C). Differences in capillary zone electrophoresis (CZE) and sodium dodecyl sulfate (SDS) – polyacrylamide gel electrophoresis (PAGE) patterns between coagulates from samples of an Israeli SW and a U.S. commercial HRW wheat were seen at all the coagulation temperatures. SDS-PAGE patterns of coagulates obtained at lower temperatures exhibited relatively more intense bands of higher molecular weight components, and those obtained at higher temperatures exhibited relatively more intense bands of lower molecular weights.     

Effect of high-nitrogen fertilizer on gliadin and glutenin subproteomes during kernel development in wheat(Triticum aestivum L.)

Nitrogen(N),a macronutrient essential for plant growth and development,is needed for biosynthesis of protein and starch,which affect grain yield and quality.Application of high-N fertilizer increases plant growth,grain yield,and flour quality.In this study,we performed the first comparative analysis of gliadin and glutenin subproteomes during kernel development in the elite Chinese wheat cultivar Zhongmai 175 under high-N conditions by reversed-phase ultra-performance liquid chromatography and twodimensional difference gel electrophoresis(2D-DIGE).Application of high-N fertilizer led to significant increases in gluten macropolymer content,total gliadin and glutenin content,and the accumulation of individual storage protein components.Of 126 differentially accumulated proteins(DAPs)induced by high-N conditions,24 gliadins,12 high-molecularweight glutenins,and 27 low-molecular-weight glutenins were significantly upregulated.DAPs during five kernel developmental stages displayed multiple patterns of accumulation.In particular,gliadins and glutenins showed respectively five and six accumulation patterns.The accumulation of storage proteins under high-N conditions may lead to improved dough properties and bread quality.     

Effect of pH and temperature on the immunogenicity of glycinin (Glycine max L.)

Sensitive immunologic techniques for the detection of alterations that occur in protein antigens were used to evaluate the immunogenicity of soybean glycinin after isolation, heat denaturation and pH alteration. The objective was to determine the effect of these agents on the immunogenic ability of this protein fraction. Immunologic assays performed on heat-denatured glycinin up to 80°C in the presence of antinative glycinin serum demonstrated that glycinin retains its immunogenic properties. Above 90°C this biological property begins to disappear, with protein insolubilization and epitope modification due to the conformational changes imposed by temperature. A reduction in immunogenicity also occurred when glycinin was taken to pH 2.0 (below its pl) and pH 11.00 (above its pl) and exposed to high temperatures in the presence of native antiglycinin serum. From these data one can conclude that, at extreme pH values, intramolecular reactions may occur which, in combination with the structural disorganization caused by high temperatures, may contribute to the reduction of immunogenicity.     

Effect of temperature, time and wheat gluten moisture content on wheat gluten network formation during thermomolding

A plastic-like material can be obtained by thermomolding wheat gluten protein which consists of glutenin and gliadin. We studied the effect of molding temperature (130-170 °C), molding time (5-25 min) and initial wheat gluten moisture content (5.6-18.0%) on the gluten network. Almost no glutenins were extractable after thermomolding irrespective of the molding conditions. At the lowest molding temperature, the extractable gliadin content decreased with increasing molding times and moisture contents. This effect was more pronounced for the α- and γ-gliadins than for the ω-gliadins. Protein extractabilities under reducing conditions revealed that, at this molding temperature, the cross-linking was predominantly based on disulfide bonds. At higher molding temperatures, also non-disulfide bonds contributed to the gluten network. Decreasing cystine contents and increasing free sulfhydryl and dehydroalanine (DHA) contents with increasing molding temperatures and times revealed the occurrence of β-elimination reactions during thermomolding. Under the experimental conditions, the DHA derived cross-link lanthionine (LAN) was detected in all gluten samples thermomolded at 150 and 170 °C. LAN was also formed at 130 °C for gluten samples containing 18.0% moisture. Degradation was observed at 150 °C for samples thermomolded from gluten with 18.0% moisture content or thermomolded at 170 °C for all moisture contents.     

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.     

Comparison of attrition in citric acid modified soybean hulls and commercial cation exchange resins

The integrity of ion exchange media used under conditions of different times of use, temperatures and pH values is important in its selection. This study was conducted to quantify the lack of integrity (attrition) in base-extracted (BE), citric acid (CA)-modified soybean hulls, a lignocellulosic cation exchange material and compare its attrition to two synthetic, commercial cation exchange resins. Attrition was determined in both batch and column operations. Batch studies included measuring attrition over a 24 h period under conditions of constant pH, variable pH and at different temperatures. Under conditions of a constant pH of 4.8, 25°C and using a stir bar, modified hulls had mostly lower attrition than the two commercial products. Under acidic conditions, modified hulls demonstrated very low (<5%) attrition. At alkaline pH values, modified hulls had higher attrition than the resins after 24 h of stirring at 25°C. Although attrition increased at alkaline pH, the modified hulls ability to bind copper ion (Cu²⁺) was unaffected by pH. After 24 h shaking at 65 and 85°C, modified hulls also had greater attrition than the synthetic polymers. At these temperatures, a decreased ability of the modified hulls to bind copper ion was observed compared to the lower temperatures of 25 and 45°C. When the products were compared in column experiments at 25°C, all materials had low (<10%) attrition. Our studies indicate that in terms of product integrity, modified soybean hulls could be useful in several applications requiring a metal ion adsorbent, but not necessarily at high temperatures.     

Net photosynthetic rate of potato at high temperatures

Summary Potato cultivars were grown in a glasshouse and plants periodically transferred to a growth chamber. When the ambient temperature in the growth chamber was raised from 15 to 40°C in steps of 5°C per hour, net photosynthetic rate decreased at temperatures above 20°C. At 40°C the rate was 37% of the rate at 20°C. A greater decrease in net photosynthetic rate occurred with plants of the cultivar Up-to-Date than with cultivars R100 and BP13. Low values of leaf diffusive resistance were recorded and changes in photosynthetic rate could not be explained by changes in this factor. When a constant ambient air temperature of 20°C was maintained while soil temperature was increased, net photosynthetic rate decreased.     

Thermal inactivation of Plasmodiophora brassicae Woron. and its attempted control by solarization in the Salinas Valley of California

Thermal inactivation of resting spores of P. brassicae Woron. in glasshouse soil depended on temperature, duration of treatment, inoculum concentration, and soil moisture. At 42, 44 and 50°C, the relationship between temperature and the time for thermal inactivation plotted on a semi-log scale was linear. Treatment times up to 45 days at 30°C and 37°C did not reduce infectivity. The detection threshold in the system was 10^0·5 spores/g of soil. At all temperatures tested, inactivation was achieved more rapidly in soil infested with 10² spores/g than with 10⁶ spores/g. Heat treatment was more effective in saturated soil than in half-saturated soil. Soil temperatures in the field in the northern Salinas Valley were increased 11–14°C by tarping with clear, polyethylene plastic. The average weekly maximum temperature and minimum temperature at a 10 cm depth under tarps were 38°C and 29°C respectively. Solarization reduced disease development after a 10-week treatment but not after a 5-week treatment.     

Changes in the potato (Solanum tuberosum L.) tuber at the onset of dormancy and during storage at 23°C and 3°C. II. Evaluation of protein patterns

Summary The changes in polypeptide profiles (2D-PAGE) occurring in the soluble and microsomal fractions of parenchymatic tissue of potato (Solanum tuberosum L.) tubers were studied during the last 30 d of maturation and during storage at 23°C and 3°C. The major changes were observed in the last period of tuber maturation, when several polypeptides disappeared and new ones appeared. At both 23°C and 3°C specific polypeptides disappeared in dormant tubers and new polypeptides appeared during storage. At 3°C specific changes in protein composition occurred, particularly in the microsomal fraction. The changes in polypeptide profiles are discussed in relation to the transition from “sink” to “source” of the tuber, the onset of dormancy and of sprouting ability and the activation of cold acclimation responses. The results are also discussed on the basis of the physiological and biochemical changes that occur in the parenchymatic tissue.     

Investigation of the high-amylose maize starch gelatinization behaviours in glycerol-water systems

The effect of glycerol on gelatinization behaviours of high-amylose maize starch was evaluated by confocal laser scanning microscopy (CLSM), scanning electronic microscope (SEM), differential scanning calorimetry (DSC), texture analyzer (TPA) and rheometer. Gelatinization of the high-amylose maize starches with glycerol content of 10% (w/w) began at 95.4 °C (T_o), peaked at 110.3 °C (T_p), and completed at 118.9 °C (T_c). The birefringence began to disappear at around 100 °C and finished at 120 °C which corresponded well to the onset and conclusion temperatures obtained by DSC. The high-amylose maize starch granules maintained original morphological structure at 100 °C and swelled to a great degree at 110 °C. The high-amylose maize starch paste formed at 100 °C showed the lowest hardness (39.92 g), while at 120 and 130 °C, showed the highest hardness (610.89 g and 635.43 g, respectively). It should be noted that in going from 100 °C to 110 °C there is a significant increase in the viscosity of the slurry solution. The identical apparent viscosity was observed when the shear rate exceed 100 s⁻¹, resulting from the high-amylose maize starch granules were completely gelatinized at 120 °C, which was consistent with DSC analysis.     

Viscoelastic properties of tablets from Osborne solubility fraction,pentosans, flour and bread using relaxation tests

There is no previously published data covering the viscoelasticity of Osborne protein solubility fractions. Therefore, the objective of this study was to compare the viscoelastic properties of Osborne fractions, water soluble pentosans, flour and bread using relaxation tests. Sintered tablets from glutenins presented similar elasticity as gliadins but almost twice the viscosity. However, most of the wheat viscoelasticity performance in tablets was given by the sum of the non-gluten components (albumins, globulins, residue and especially water soluble pentosans). The residue was 86.1% w/w in flour and contained 4% protein while its estimated viscoelastic effect was higher compared to all the other flour components. Regarding the estimated viscosity in flour due to protein from specific fractions, it was higher in gliadins compared to glutenins. The residue although has low protein in flour (4.0%), the large amount of residue in flour had significant viscoelastic effect. The viscoelasticity of water soluble pentosans corrected by weight was similar to the Osborne protein fractions. The results indicate that the starch, pentosans, and non-gluten components may not be considered merely as inert filler and play a major role in determining the viscoelastic nature of flour and bread.     

Changes in pasta proteins induced by drying cycles and their relationship to cooking behaviour

Spaghetti produced in a pilot plant was dried using three different drying conditions: 60 °C for 7.5 h; 75 °C for 5.5 h; 90 °C for 5 h. Proteins of spaghetti were characterized by size-exclusion chromatography (SEC) and size-exclusion–high-performance liquid chromatography (SE-HPLC). As the temperature of the drying cycles increased, a progressive decrease of the small and large monomeric proteins and an increase in molecular size of the large polymeric proteins (LPPs) were observed. Drying temperature at 60 °C already induces a significant increase in the molecular size of the LPPs and a significant decrease of the other protein fractions. At 70 and 90 °C, large and small monomeric proteins as well as LPPs polymerized as seen by a progressive shift towards higher molecular weights in the SEC profile as temperature increased. The changes in the chromatographic profiles were accompanied by increasing amount of total unextractable polymeric protein (UPP). A decrease in stickiness and an increase in firmness corresponded to the formation of large and insoluble protein aggregates.     

Evaluation of Laundering Durability of Electro-conductive Textile Dip-coated on Para Aramid Knit with Graphene/Waterborne Polyurethane Composite

This study aims to fabricate an electro-conductive textile dip-coated with graphene/waterborne polyurethane (WPU) composite, and an evaluation of the laundering durability of this composite was conducted in order to confirm the application of the protective clothing. Samples were coated five times on the para-aramid knit with the graphene/WPU composite by the dip-coating method, and then hot-pressed processes were applied with various temperatures. The samples were washed 5, 10, 15, and 20 times, and then, morphology, surface resistance, and surface temperature were measured. After five laundering cycles, control and hot-pressed samples maintained surface resistivity from 10 kΩ/sq to 100 kΩ/sq. The surface resistivity of the control sample, however, was gradually increased up to 20 laundering cycles. The sample that was hot-pressed at 120 °C showed the lowest value of about 15 kΩ/sq with almost no variation from zero laundering cycles to 20, thus, it is the most stable sample up to 20 laundering cycles. When applied voltage at 50V, the surface temperature of the nonlaundering samples was presented as over 40.0 °C. In the case of the control sample, there was almost no electrical heating performance remaining after the fifth laundering test, but the hot-pressed samples maintained 40.0 °C or more at 50 V after the 10th laundering test. The sample that was hot-pressed at 120 °C in particular could maintain electrical heating performance at about an 80 % level up to the 10th laundering cycle. Therefore, the sample that was hot-pressed at 120 °C was the most stable in terms of electrical properties after 20 laundering cycles, and its electrical heating performance could be maintained even after 10 laundering cycles. It is expected that this process can be applied and used to make functional clothes for apparel and other applications.     

Extractability and chromatographic separation of rye (Secale cereale L.) flour proteins

A size exclusion – high performance liquid chromatography (SE-HPLC) method originally developed for separating wheat, barley or rice proteins was applied to study the extractability and molecular weight (MW) distribution of rye flour proteins. These were extracted with 50 mmol/l sodium phosphate buffer (pH 6.8) containing 2.0% (w/v) sodium dodecyl sulfate (SDS) and, optionally, 1.0% (w/v) dithiothreitol (DTT). About 95% of the proteins were extracted in buffer containing 2.0% SDS. Addition of 1.0% DTT to such buffer increased the protein extractability to 100%, indicating that rye flour contains some proteins cross-linked by disulfide (SS) bonds. The SE-HPLC profiles revealed that rye flour contains SS-linked HMW-secalins and 75 k γ-secalins which elute in specific peaks. Upon reduction, these SS-linked protein aggregates dissociate and some entrapped albumins, globulins and/or ω-secalins are released. Rye flour albumins and globulins elute over the entire SE-HPLC profile. In contrast, the monomeric ω-secalins and 40 k γ-secalins are detected in specific well resolved SE-HPLC peaks. The applied fast and reproducible method can be used to characterise and quantify rye flour proteins and to determine changes as a result of processing.     

Significant down-regulation of γ-gliadins has minor effect on gluten and starch properties of bread wheat

The contribution of gliadins to the baking performance of wheat has been widely discussed. In the present study we report the properties of the flours of fifteen transgenic wheat lines with γ-gliadins down-regulated by RNAi. Technological properties were assessed by sodium dodecyl sulfate sedimentation (SDSS) test, and rheological properties were characterized during mixing using the Mixolab^®. Changes in the proportions of gluten proteins, with significant increases of glutenins, were observed in transgenic lines. These changes did not affect the SDSS test in most of the transgenic lines. The dough strength of some transgenic lines was reduced as determined by the Mixolab^®. Changes in the starch behavior were also observed in the transgenic lines, in which lower values of torque were observed at the C3, C4 and C5 points of the mixing curve. The results reported here are important in understanding the role of γ-gliadins in the bread-making quality of flours.     

Properties of Frozen Wheat Doughs at Subzero Temperatures

The subzero properties of wheat doughs were measured by dynamic mechanical thermal analysis (DMTA) and dielectric thermal analysis (DETA) over the temperature range −90 to +40 °C and by¹H-nuclear magnetic resonance (NMR) T₂relaxation over the range −45 to 0 °C. The experiments revealed two transitions in the dough: one independent of frequency at −10 °C (attributed to ice melting) and one dependent on frequency at −30 °C (attributed to a glass transition). The glass transition temperatures measured by DMTA moved to higher temperatures during frozen storage when the optimal water content of dough was used. A reduction in the water content eliminated this phenomenon. A similar effect of water reduction was observed by NMR studies, in which amplitude ratios and decay times were used to calculate the phase transitions. However, the glass transition recorded by NMR was independent of frozen storage with optimal water content. The changes of water state in frozen doughs were studied by ultracentrifugation (the amount of liquid phase) and NMR (freezable water based on liquid amplitude ratios). Frozen storage increased the liquid phase in dough with optimal water content. Thus, ice crystals are growing during frozen storage resulting in the concentration of polymers and a higher glass transition observed by DMTA. The increase of liquid phase during storage was substantially lower when the water content of dough was decreased. Ice crystals» growth can be minimised by reducing water content. The experiments were carried out with four different flours. The measurement of glass transition temperature by DMTA, DETA or NMR did not reveal great differences in doughs made from different flours. The amount of liquid phase was strongly flour dependent.