Optimisation of a solvent for the complete extraction of prolamins from heated foods

Wheat bread was lyophilised, ground, extracted and centrifuged. The supernatants were analysed for gluten content by RP-HPLC and a commercial sandwich ELISA. Prolamin extraction solvents contained tris(2-carboxyethyl)phosphine (TCEP; 1, 2, 5, 10, 20, 50 mmol/L), guanidine hydrochloride (GUA; 0 or 2 mol/L) and a buffered salt solution. A commercial cocktail solution (250 mmol/L mercaptoethanol (ME), 2 mol/L GUA, buffered salt solution) as well as 60% (v/v) ethanol were used as control solvents. Wheat flour was the control for the extractability of the native prolamins. 60% ethanol only extracted 37% of the prolamins from wheat bread (cocktail = 100%). When ME was replaced by TCEP the protein yield increased from 35% at the lowest TCEP-level to 95% when 20–50 mmol/L TCEP were used. The use of GUA was essential to extract prolamins quantitatively. Comparative protein analysis using RP-HPLC and ELISA showed that both methods provided comparable prolamin (gliadin) concentrations of the wheat flour (40.3–45.7 mg/g), when 60% ethanol was used as extraction solvent. The extraction yields from bread were considerably lower (16.7–24.7 mg/g). Cocktail and TCEP extracted almost the same amount of protein from flour and bread with TCEP showing slightly lower yields. Total extractable protein (gliadin + glutenin) as determined by RP-HPLC was 70.5–75.3 mg/g, and total gliadin as determined by ELISA was 42.7–44.2 mg/g. Thus, the study has shown that TCEP in combination with GUA extracts proteins from heated, gluten-containing foods as effective as the commercial cocktail solution.     

Durum wheat breadmaking quality: Effects of gluten strength,protein composition,semolina particle size and fermentation time

The effects of particle size of granulars (semolina and flour combined), gluten strength, protein composition and fermentation time on the breadmaking performance were compared for eleven durum wheat genotypes of diverse strength from North America and Italy grown in the same environment. All genotypes were γ-gliadin 45 types (low-molecular weight glutenin subunit 2 patterns) associated with superior pasta-making quality. Three cultivars with high-molecular weight glutenin subunit 20 exhibited relatively weak gluten, confirming that this subunit is associated with weakness in durum wheat. Gluten strength as measured by a range of technological tests was directly and strongly related to the proportion of insoluble glutenin (IG) in granulars protein as determined by a spectrophotometric procedure. Reducing the particle size of granulars by gradual reduction shortened development time in both the farinograph and mixograph. Reducing granulars also increased starch damage and, accordingly, farinograph water absorption, but remix-to-peak baking absorption was unaffected due to increased fermentation loss for finer granulars. Neither loaf volume, nor remix-to-peak mixing time were affected by the particle size of the granulars indicating that regrinding is not an asset for baking provided there is adequate gassing power. Loaf volume was directly related to gluten strength and IG content, and inversely related to residue protein, a non-gluten containing fraction. When fermentation time was reduced from the standard 165 to 90 min and 15 min, all genotypes exhibited a progressive increase in loaf volume. Therefore, regardless of strength, short fermentation time is preferred when high volume durum wheat bread is desired. Some of the stronger durum genotypes exhibited remix-to-peak bread volume comparable to that expected of good quality bread wheat, indicating that there is potential to select for genotypes with improved baking quality in conventional breeding programs by screening for high content of insoluble glutenin.     

Sourdough fermentation of wholemeal wheat bread increases solubility of arabinoxylan and protein and decreases postprandial glucose and insulin responses

Glycemic responses to most of the conventional breads are high, including breads made of wholemeal flour. Baking technology is known to affect these responses. The aim of the present study was to investigate effects of xylanase enzyme treatment and sourdough fermentation in wholemeal wheat bread baking on postprandial glucose and insulin responses and on in vitro protein digestibility. The wheat breads were made of 100% flour from peeled kernels by a straight dough or sourdough fermentation method, and with or without using xylanase during mixing of dough. Standard white wheat bread was used as a reference. All test bread portions contained 50 g available carbohydrate and were served in random order to eleven insulin resistant subjects. Blood samples for measuring glucose and insulin concentrations were drawn over 4 h. The sourdough wholemeal wheat bread resulted in the lowest postprandial glucose and insulin responses among the four tested breads (treatment × time; p = 0.000 and p = 0.022, respectively). There were differences in solubility and depolymerisation of protein and arabinoxylan among the breads but these did not fully explain the in vivo findings. In conclusion, the health effects of wholemeal wheat bread can be further improved by using sourdough process in breadmaking.     

Genetic responses in milling,flour quality,and wheat sensitivity traits to grain yield improvement in U.S. hard winter wheat

A rising global population necessitates continued genetic improvement of wheat (Triticum spp.), but not without monitoring of unintended consequences to processors and consumers. Our objectives were to re-establish trends of genetic progress in agronomic and milling traits using a generational meter stick as the timeline rather than cultivar release date, and to measure correlated responses in flour quality and human wheat-sensitivity indicators. Grain yield and kernel size showed stepwise increases over cycles, whereas wheat protein content decreased by 1.1 g/100 g. Reduced protein content, however, did not result in lower dough strength pertinent to bread baking. A novel method of directly testing gluten elasticity via the compression-recovery test indicated a general increase in gluten strength, whereas the ratio of total polymeric to total monomeric proteins remained stable. Also showing no change with genetic progress in yield were flour levels of gluten epitopes within the key immunotoxic 33-mer peptide. The oligosaccharide fructan, present in milled and wholemeal flours, increased with increasing grain yield potential. While yield improvement in U.S. bread wheat was not accompanied by a decline in gluten strength or systematic shift in a key wheat sensitivity parameter, the unanticipated rise in total fructans does implicate potentially new dietary concerns.     

The influence of temperature extremes on some quality and starch characteristics in bread,biscuit and durum wheat

Environmental conditions during grain-fill can affect the duration of protein accumulation and starch deposition, and thus play an important role in grain yield and flour quality of wheat. Two bread-, one durum- and one biscuit wheat were exposed to extreme low (−5.5 °C for 3 h) and high (32 °C/15 °C day/night for three days) temperatures during grain filling under controlled conditions for two consecutive seasons. Flour protein content was increased significantly in one bread wheat, Kariega, under heat stress. Cold stress significantly reduced SDS sedimentation in both bread wheats. Kernel weight and diameter were significantly decreased at both stress treatments for the two bread wheats. Kernel characteristics of the biscuit wheat were thermo stable. Kernel hardness was reduced in the durum wheat for the heat treatment. Durum wheat had consistently low SDS sedimentation values and the bread wheat high values. Across the two seasons, the starch content in one bread wheat was significantly reduced by both high and low temperatures, as is reflected in the reduction of weight and diameter of these kernels. In the durum wheat, only heat caused a significant reduction in starch content, which is again reflected in the reduction of kernel weight and diameter.     

Dehydration of gluten matrix as a result of dietary fibre addition – A study on model flour with application of FT-IR spectroscopy

Nowadays, consumers demand dietary fibre-enriched products of appropriate taste, texture, smell and appearance. Unfortunately, addition of the dietary fibre supplements to bread significantly reduces its quality which is connected with changes in the structure of gluten proteins. Structural changes as well as changes in the water state of gluten matrix induced by eight dietary fibres were observed by using Fourier transform infrared spectroscopy. To facilitate this the difference spectra were calculated by subtraction of the control (gluten only) infrared spectrum from the spectra of gluten-fibre mixtures. The presence of positive bands at ca. 1597 and 1235 cm⁻¹ indicated aggregation of gluten proteins into hydrogen bonded β-sheets. These β-sheets can be formed by other β-sheets, antiparallel-β-sheets, β-turns and/or α-helices. The aggregation is probably induced by partial dehydration of gluten matrix due to competition for water molecules between gluten proteins and fibre polysaccharides. This assumption is confirmed by the presence of the negative band at 3237 cm⁻¹ and decrease in the intensity of the band at 3051 cm⁻¹. These bands are assigned to the weak and strong H-bonds in the gluten matrix, respectively. The results indicated that both weak and strong H-bonds are necessary to dough formation of adequate rheological properties.     

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.     

Dough quality of bread wheat lacking α-gliadins with celiac disease epitopes and addition of celiac-safe avenins to improve dough quality

Celiac disease is a T-cell mediated immune response in the small intestine of genetically susceptible individuals caused by ingested gluten proteins from wheat, rye, and barley. In the allohexaploid bread wheat (Triticum aestivum), gluten proteins are encoded by multigene loci present on the homoeologous chromosomes 1 and 6 of the three homoeologous genomes A, B, and D. The effect of deleting individual gluten loci was analyzed in a set of deletion lines of T. aestivum cv. Chinese Spring with regard to the level of T-cell stimulatory epitopes (Glia-α9 and Glia-α20) and to technological properties of the dough including mixing, stress relaxation, and extensibility.     

Ecophysiological determinants of biomass and grain yield of wheat under P deficiency

Grain yield of crops can be expressed as a function of the intercepted radiation, the radiation use efficiency and the partitioning of above-ground biomass to grain yield (harvest index). When a wheat crop is grown under P deficiency the grain yield is reduced but it is not clear how these three components are affected. Our aim was (i) to identify which of these components were affected in spring bread wheat under P deficiency at field conditions and (ii) to relate the grain yield responses to processes of grain yield formation during the spike growth period. Three field experiments were conducted in the potentially high wheat yielding environment of southern Chile. All experiments had two levels of P availability: with (155 kg P ha⁻¹) or without P fertilization (average soil P-Olsen concentration of 10 ppm, a medium level of P availability). High wheat grain yields were obtained varying between 815 and 1222 g m⁻² with P applications. Experiments showed a grain yield reduction caused by P deficiencies of 35, 16 and 18% in experiments 1, 2 and 3, respectively. This was related (R² = 0.99, P < 0.01) to a reduction in the total above-ground biomass at harvest and not to the harvest index. Reductions in above-ground biomass were due to a reduction in radiation intercepted under P deficiency without effecting radiation use efficiency. Grain number per square meter was the main yield component (R² = 0.99, P < 0.01) that explained the grain yield reduction caused by the P deficiency which was due to low spike biomass at anthesis (R² = 0.96, P < 0.05). The reduction in spike biomass at anthesis was related (R² = 0.86, P < 0.01) to reductions in crop growth rate during the spike growth period as a consequence of a lower radiation intercepted during this period. This study showed that under high wheat yield conditions the main effect of a P deficiency on grain yield reduction was a negative impact on the total above-ground biomass due to the negative impact on intercepted radiation, particularly during the spike growth period, affecting negatively spike biomass at anthesis and consequently grain number and yield.     

Modification of the rheological behavior of amaranth (Amaranthus hypochondriacus) dough

For people with celiac disease, a lifelong abdication of gluten including-products is necessary to live a life without celiac affected reactions. The production of high-quality bread from gluten free flour is not simple in comparison to gluten including flours such as those derived from wheat (Triticum spp.). The gas binding and crumb structure forming capacity are very low in gluten free batters. They can efficiently be analyzed through the rheological properties of the dough used. The use of acidification in amaranth (Amaranthus hypochondriacus) dough preparation is a possible means of changing the rheological behavior of amaranth in the desired direction. Methods include the use of lactic acid directly, or the fermentation via lactic acid bacteria. Adding up to 20 mL lactic acid/kg flour in amaranth dough preparation led, during oscillation tests, to an increase of the complex shear modulus up to 30% in the range of 0.1 up to 10 Hz. The use of sourdough fermentation decreased the complex shear modulus in the same test up to nearly 60%. In creep recovery tests, the elastic part of amaranth dough decreased from 65.4% without any treatment down to 63.9% by the addition of up to 20 mL lactic acid/kg flour. Sourdough fermentation by Lactobacillus plantarum was able to decrease it to 54%. The acidification showed a significant positive influence on the rheological parameters of amaranth dough only at the higher stress level. In contrast, sourdough fermentation was able to produce doughs with viscosity and elasticity similar to that found in pure wheat flours.     

河北省主要推广强筋小麦的面包加工品质

为了解河北省主推强筋小麦品种的籽粒品质和面包加工品质,评选优质面包小麦品种,对河北省9个强筋小麦品种的31个籽粒品质和8个面包加工品质指标进行了测定。结果表明,除千粒重、容重、籽粒硬度、出粉率、面粉色泽L*值、面粉色泽b*值、面粉白度、籽粒蛋白质含量、湿面筋含量、糊化温度、吸水率外,其余被测指标的变异系数均大于10%,说明河北省强筋小麦品种多数品质性状的遗传多样性比较丰富。藁优9415、冀师02-1、藁优2018和金麦1号4个小麦品种制作的面包达到国家优质面包标准。面包评分与面团拉伸曲线面积和最大拉伸阻力极显著正相关,与形成时间、稳定时间、粉质质量指数、延伸度和拉伸阻力显著正相关,与面包质构的粘聚性极显著正相关,与面包质构的硬度、胶着性、咀嚼度、坚实度均极显著负相关。     

Use of chemical redox agents and exogenous enzymes to modify the protein network during breadmaking – A review

During breadmaking, a continuous protein network is formed which confers visco-elasticity to dough. The properties of this protein network are highly dependent on the characteristics of the gluten proteins of the wheat flour. A good quality (highly elastic) gluten network retains the carbon dioxide that is produced by the yeast, giving dough and bread with optimal properties. However, the properties of the gluten proteins can differ substantially between wheat flours and are highly dependent on genetic, environmental and post-harvest conditions. Deficiencies in wheat quality for breadmaking can be overcome by incorporating exogenous components which alter the functionality of the gluten proteins during breadmaking. These include additives (e.g. potassium bromate, iodate, chlorine dioxide and chlorine, azodicarbonamide, ascorbic acid and peroxides) and enzymes affecting protein crosslinking. Transglutaminase, glucose oxidase, hexose oxidase and laccase all promote the formation of covalent bonds between gluten proteins and, hence, can serve as alternatives to chemical bread improvers.     

Effect of the grain protein content locus Gpc-B1 on bread and pasta quality

Grain protein concentration (GPC) affects wheat nutritional value and several critical parameters for bread and pasta quality. A gene designated Gpc-B1, which is not functional in common and durum wheat cultivars, was recently identified in Triticum turgidum ssp. dicoccoides. The functional allele of Gpc-B1 improves nitrogen remobilization from the straw increasing GPC, but also shortens the grain filling period resulting in reduced grain weight in some genetic backgrounds. We developed isogenic lines for the Gpc-B1 introgression in six hexaploid and two tetraploid wheat genotypes to evaluate its effects on bread-making and pasta quality. In common wheat, the functional Gpc-B1 introgression was associated with significantly higher GPC, water absorption, mixing time and loaf volume, whereas in durum wheat, the introgression resulted in significant increases in GPC, wet gluten, mixing time, and spaghetti firmness, as well as a decrease in cooking loss. On the negative side, the functional Gpc-B1 introgression was associated in some varieties with a significant reduction in grain weight, test weight, and flour yield and significant increases in ash concentration. Significant gene × environment and gene × genotype interactions for most traits stress the need for evaluating the effect of this introgression in particular genotypes and environments.     

Gluten and non-gluten proteins of wheat as target antigens in autism,Crohn’s and celiac disease

Studies show that patients with celiac disease react not only with gluten wheat proteins but also with non-gluten wheat components. Our goal was to measure IgG or IgA antibodies against wheat proteins or peptides that would provide the most sensitive method for the detection of wheat immune reaction in children with autism spectrum disorder, and patients with Crohn’s and celiac disease (CD). Using ELISA, we measured these antibodies against various gluten and non-gluten wheat proteins. Compared to controls in all three conditions, the strongest reaction was against CXCR3-binding gliadin peptide, followed by a wheat protein mixture, and α-gliadin 33-mer peptide. We determined that a sample that strongly reacted against non-gluten proteins also reacted strongly against gluten proteins. We also found that IgA antibodies against CXCR3-binding gliadin peptide were strongly reactive in a subgroup of 33% in the autism group, 42% in the Crohn’s group, and all tested samples with CD. The results indicate that measuring IgG and IgA antibodies against non-gluten proteins adds nothing to the pathologic relevance of these antibodies. Further research is needed on CXCR3-binding gliadin peptide antibodies as a possible biomarker and as a guide for dietary elimination in CD, Crohn’s disease and a subgroup of children with ASD.     

Comparative analysis of dough rheology and quality of bread baked from fortified and high-in-fiber flours

The research, evaluated the rheological properties of dough and final bread quality production, in function of time, made from wheat refined flour that was enriched with an oat dietary fiber in two dosages (WOF 6% and WOF 12%), spelt flour and two types of wholegrain flour: wholegrain (full milling) and wholemeal (one-step milling). The rheological measurements revealed that the highest instantaneous compliance (J₀) was observed in the wholemeal sample and the lowest was in the WOF 6%. The lowest specific volume was observed in the wholegrain bread (0.82 cm³/g), while the highest was observed in the control white bread sample (1.60 cm³/g). The most rapid loss of moisture appeared in white bread. The moisture content was significantly influenced by the type of flour, day of storage and the interaction of these two variables (p ≤ 0.01). The hardest was the sample of wholegrain bread on the first and third day. The smallest pores were noticed in WOF 12% sample. In water extraction, white bread and WOF 12% were comparable and there were no significant differences between spelt bread and wholegrain bread. THE WOF 12% sample had the optimal ratio of health benefits and technological properties.     

Development of an Aegilops longissima substitution line with improved bread-making quality

This study focuses on the effect of Aegilops longissima on wheat bread making quality. Chromosome 1S^l disomic addition line of Ae. longissima (DAL1S^l) had significantly higher dough strength, grain hardness, mixographic peak height, band width, and unextractable polymeric protein content compared with wheat. DAL1S^l also had additional glutenin and gliadin proteins contributed by Ae. longissima. The larger size of 1S^l coded HMW-GSs sequenced from DAL1S^l and their phylogenetic similarity to the D-genome-coded subunits were suspected to be one of the major reasons for the increased dough strength of DAL1S^l. To transfer the chromosome 1S^l genes responsible for the good bread-making quality to wheat, we generated a chromosome-specific disomic substitution line [DSL1S^l(1A)] by crossing DAL1S^l with nulli 1A tetra 1B genetic stock and further selection. Grain quality analysis revealed significantly lower grain hardness and significantly higher dough strength, farinograph development time, stability time, gluten index, bread loaf volume, and bread quality score in DSL1S^l(1A), compared with wheat. However, the increased bread loaf volume and quality were not proportional to the relatively higher increases in dough strength and gluten index, indicating importance of other traits influencing bread making quality. The presence of a minor hardness locus on chromosome 1A is speculated.     

Endogenous redox agents and enzymes that affect protein network formation during breadmaking – A review

During breadmaking, wheat gluten proteins form a continuous network which is stabilized by disulfide bonds and modified by thiol/disulfide interchange reactions. This gluten network results in visco-elastic dough that holds together the other dough components and assists in retaining carbon dioxide. Wheat flour contains several components, enzyme co-factors and enzymes which can affect the formation and properties of the gluten network and, hence, the dough and bread characteristics. We present a brief overview of our current knowledge of the fate of gluten proteins during breadmaking, and how they are affected by endogenous wheat components (e.g. glutathione, cysteine and NAD(P)(H)) and enzyme systems (e.g. tyrosinase, peroxidase, the NADP-dependent thioredoxin and glutathione enzyme systems, protein disulfide isomerase, lipoxygenase, catalase and dehydrogenases).     

Using stress tolerance indicator (STI) to select high grain yield iron-deficiency tolerant wheat genotypes in calcareous soils

Despite large variation among crop genotypes in response to Fe fertilization, there is no reliable indicator for identifying Fe-deficiency tolerant wheat genotypes with high grain yield. The aim of this investigation was to compare the grain yield response of 20 spring and 30 winter bread wheat genotypes to Fe fertilization under field conditions and to select high grain yield Fe-deficiency tolerant genotypes using a stress tolerance indicator (STI). Two individual trials, each one consisting two field plot experiments, were conducted during 2006–2007 and 2007–2008 growing seasons. Spring wheat genotypes (Trial l) and winter wheat genotypes (Trial 2) were planted at two different locations. Two Fe rates (0 and 20 kg Fe ha⁻¹ as Fe-EDTA) were applied. Spring and winter wheat genotypes differed significantly (P < 0.01) in the grain yield both with and without added Fe treatments. Application of Fe fertilizer increased grain yield of spring wheat genotypes by an average of 211 and 551 kg ha⁻¹ in Karaj and Isfahan locations, respectively. By Fe application, the mean grain yield of winter wheat genotypes increased 532 and 798 kg ha⁻¹ in Karaj and Isfahan sites, respectively. Iron efficiency (Fe-EF) significantly differed among wheat genotypes and ranged from 65% to 113% for spring wheat and from 69% to 125% for winter wheat genotypes. No significant correlation was found between Fe-EF and grain yield of spring wheat genotypes under Fe deficient conditions. For winter wheat genotypes grown in Mashhad, Fe-efficiency was not significantly correlated with the grain yield produced without added Fe treatment. The STI was significantly (P < 0.01) varied among spring and winter wheat genotypes. The interaction between location and genotype had no significant effect on the STI. According to these results, the STI should be considered as an effective criterion for screening programs, if a high potential grain yield together with more stable response to Fe fertilization in different environments is desired.     

Improving wheat to remove coeliac epitopes but retain functionality

Coeliac disease is an intolerance triggered by the ingestion of wheat gluten proteins. It is of increasing concern to consumers and health professionals as its incidence appears to be increasing. The amino acid sequences in gluten proteins that are responsible for triggering responses in sensitive individuals have been identified showing that they vary in distribution among and between different groups of gluten proteins. Conventional breeding may therefore be used to select for gluten protein fractions with lower contents of coeliac epitopes. Molecular breeding approaches can also be used to specifically down-regulate coeliac-toxic proteins or mutate coeliac epitopes within individual proteins. A combination of these approaches may therefore be used to develop a “coeliac-safe” wheat. However, this remains a formidable challenge due to the complex multigenic control of gluten protein composition. Furthermore, any modified wheats must retain acceptable properties for making bread and other processed foods. Not surprisingly, such coeliac-safe wheats have not yet been developed despite over a decade of research.     

Elastic properties of gluten representing different wheat classes

Traditional instruments used to evaluate dough and/or gluten rheological properties do not provide unambiguous separation of elastic and viscous behaviors. Recovery after shear creep and cyclic large deformation cyclic tensile testing were used here to decouple elastic and viscous effects. A large variation in the recoverable shear strain (∼7.2% to ∼28%) was seen for glutens from 15 U.S. popular common wheat cultivars with varying HMW subunits. Sedimentation values ranged from 29 to 57 ml for 12 hard wheat cultivars and 15 to 22 ml for three soft wheat cultivars. The tensile force at 500% extension ranged from 0.12 to 0.67 N for hard wheat glutens and from 0.10 to 0.20 for soft wheat glutens. However, the recoverable work after large extension was less than 40% of the total work of extension. In addition, recoverable work in tensile testing was highly correlated with the total work of extension (r² = 0.97) and mixograph mix times (r² = 0.81). Good to excellent bread volume was obtained for several cultivars from this sample set. This suggests that optimizing water absorption for mixing doughs to achieve maximal bread volume compensates for the wide range of viscoelastic behaviors of gluten.