Authors:J. Wang, J. Chen, F. Dai, F. Wu, J. Yang, and G. Zhang
The effects of sowing date, nitrogen application level and timing on barley protein components and malt quality were investigated. There was a significant difference in total protein and its protein fractions among the four barley genotypes. The protein component was changeable over the different growing conditions, and the extent of change varied with protein fraction and genotype. Marked variation in malt quality over the different environments (sowing date, N fertilizer rate and applying time) was also observed. Increased N fertilizer application increased diastatic power (DP) value, but reduced malt extract. Grain protein content was significantly and positively correlated with albumin, globulin and hordein, but was not correlated with glutelin. However, glutelin was significantly related to other malt quality parameters.
Authors:S. Uthayakumaran, R.I. Tanner, S.-C. Dai, F. Qi, and C.W. Wrigley
Two fundamental test systems were used to evaluate the visco-elastic properties of doughs from wheat samples of three varieties grown at four distinct sites. For comparison, tests were also performed with traditional equipment, namely the Mixograph, an extension tester and a Farinograph-type small-scale recording mixer. Uniaxial dough elongation (with an Instron) produced results similar to the conventional extension tester, except that results were provided in fundamental units (Pascals), the critical value recorded being the elongational stress at maximum strain. Stress relaxation measurements were performed following a small initial shear strain. With this method, it was possible to distinguish between the viscosity and the elastic components of dough visco-elasticity. In all the tests the extra dough-strength properties were evident for the variety (Guardian) that had the 5 + 10 glutenin subunits, in contrast to the other two with the 2 + 12 combination of subunits.
Authors:S.F. Dai, X.F. Xue, Y.F. Wang, Y.L. Xie, Z.P. Song, D.Y. Xu, Z.J. Wen, and Z.H. Yan
New high-molecular-weight glutenin (HMW glutenin) sequences isolated from six Psathyrostachys juncea accessions by thermal asymmetric interlaced PCR differ from previous sequences from this species. They showed novel modifications in all of the structural domains, with unique C-terminal residues, and their N-terminal lengths were the longest among the HMW glutenins reported to date. In their repetitive domains, there were three repeatable motif units: 13-residue [GYWH(/I/Y)YT(/Q)S(/T)VTSPQQ], hexapeptide (PGQGQQ), and tetrapeptide (ITVS). The 13-residue repeats were restricted to the current sequences, while the tetrapeptides were only shared by D-hordein and the current sequences. However, these sequences were not expressed as normal HMW glutenin proteins because an in-frame stop codon located in the C-termini interrupted the intact open reading frames. A phylogenetic analysis supported different origins of the P. juncea HMW glutenin sequences than that revealed by a previous study. The current sequences showed a close relationship with D-hordein but appeared to be more primitive.
Authors:N.T. Vu, J. Chin, J.A. Pasco, A. Kovács, L.W. Wing, F. Békés, and D.A.I. Suter
To determine the prevalence of wheat sensitivity in a randomly selected Australian population, a study was carried out on sera samples of the Geelong Osteoporosis Study (GOS) age-stratified cohorts of men and women who were randomly selected from electoral rolls for the Barwon Statistical Division (n = 1145). The human sera were analysed by ELISA-based method using the ImmunoCAP 100 instrument (Phadia, Sweden). IgE from human sera were bound to the wheat (f4) and milk (f2) allergens that have been previously coated on the ImmunoCAPs. The number of IgE wheat and milk RAST positive individuals was determined. In order to relate the increased IgE immuno-reactivity to allergen symptoms, a questionnaire was established and sent to the blood donors and 974 individuals responded. Of these (n = 974) 147 individuals (15.1%) reported symptoms caused by wheat consumption, 179 (15.6%) and 112 (9.8%) sera showed RAST positive results (IgE > 60 response units) in wheat and milk RAST tests, respectively. However, only 2.5% of those participants with symptoms related to wheat had positive IgE values indicating that the relationship is complex: a large proportion (12.7%) of the investigated population might suffer from other wheat related disorders (i.e. not IgE mediated), such as celiac disease, non-celiac reaction to gluten, reaction to fructans for those with irritable bowel syndrome as well as other factors. For the 13.2% who showed raised IgE antibody levels without symptoms we postulate that these individuals have latent wheat sensitivity with the potential of developing symptoms sooner or later.A comparative study to investigate the immune reactivity of human IgE against wheat and spelt antigens was carried out using the sera of 73 patients found to be RAST positive for wheat. Of these 63% (n = 50) showed a higher IgE immune reactivity against wheat, while 30% (n = 24) showed higher IgE response against spelt antigens, the remaining 7% have indifferent responses against both antigens. Since the provided Phadia wheat and spelt antigens used in this study originated from Europe, Australian wheat and spelt varieties were also used to prepare antigens in order to investigate the response of Australian sera to local wheats. It was found that the immune reactivity of IgE wheat positive sera from a normal Australian population is lower for spelts compared to wheats regardless of their origin but much lower against an Australian spelt containing a mutation in its expansin gene. Aclinical feeding trial would be necessary to confirm if this difference in immune reactivity between spelt and wheat is consistent with a difference in allergenicity.
Authors:S.F. Dai, D.Y. Xu, Z.J. Wen, Z.P. Song, H.X. Chen, H.Y Li, J.R. Li, L.Z. Kang, and Z.H. Yan
A novel 4.0-kb Fy was sequenced and bacterially expressed. This gene, the largest y-type HMW-GS currently reported, is 4,032-bp long and encodes a mature protein with 1,321 amino acid (AA) residues. The 4.0-kb Fy shows novel modifications in all domains. In the N-terminal, it contains only 67 AA residues, as three short peptides are absent. In the repetitive domain, the undecapeptide RYYPSVTSPQQ is completely lost and the dodecapeptide GSYYPGQTSPQQ is partially absent. A novel motif unit, PGQQ, is present in addition to the two standard motif units PGQGQQ and GYYPTSPQQ. Besides, an extra cysteine residue also occurs in the middle of this domain. The large molecular mass of the 4.0-kb Fy is mainly due to the presence of an extra-long repetitive domain with 1,279 AA residues. The novel 4.0-kb Fy gene is of interest in HMW-GS gene evolution as well as to wheat quality improvement with regard to its longest repetitive domain length and extra cysteines residues.