The quality of wheat (Triticum aestivum L.) for making bread is largely due to the strength and e... more The quality of wheat (Triticum aestivum L.) for making bread is largely due to the strength and extensibility of wheat dough, which in turn is due to the properties of polymeric glutenin. Polymeric glutenin consists of high- and low-molecular-weight glutenin protein subunits linked by disulphide bonds between cysteine residues. Glutenin subunits differ in their effects on dough mixing properties. The research presented here investigated the effect of a specific, recently discovered, glutenin subunit on dough mixing properties. This subunit, Bx7.1, is unusual in that it has a cysteine in its repetitive domain. With site-directed mutagenesis of the gene encoding Bx7.1, a guanine in the repetitive domain was replaced by an adenine, to provide a mutant gene encoding a subunit (MutBx7.1) in which the repetitive-domain cysteine was replaced by a tyrosine residue. Bx7.1, MutBx7.1 and other Bx-type glutenin subunits were heterologously expressed in Escherichia coli and purified. This made it possible to incorporate each individual subunit into wheat flour and evaluate the effect of the cysteine residue on dough properties. The Bx7.1 subunit affected dough mixing properties differently from the other subunits. These differences are due to the extra cysteine residue, which may interfere with glutenin polymerisation through cross-linkage within the Bx7.1 subunit, causing this subunit to act as a chain terminator.
Cereal Chem. 73(4):478-482 A device is described for measuring rheological properties of a dough ... more Cereal Chem. 73(4):478-482 A device is described for measuring rheological properties of a dough tional viscosity was of the order 105-106 Parsec when the elongation rate sheet with an Instron universal testing machine. A mathematical analysis varied from 10-3 to 1' sec1. Water addition affected the slope and the of the setup is presented, allowing the stresses, deformation (elongation), intercept
ABSTRACT As part of our studies on the mechanisms of bread staling, starch bread was used as a re... more ABSTRACT As part of our studies on the mechanisms of bread staling, starch bread was used as a research tool that enables us to gain insights into the individual contributions that starch and gluten have on staling. Reconstitution experiments have demonstrated that bread of equivalent specific loaf volume stales at the same rate irrespective of protein concentration, or type of protein. However, other properties of bread, such as specific loaf volume, may be altered by specifically changing the protein component in the flour.
The prediction of final sheet thickness after rolling of wheat flour dough is studied using an ap... more The prediction of final sheet thickness after rolling of wheat flour dough is studied using an approximate method that concentrates on the initial, intermediate and final material configurations. A newly proposed viscoelastic constitutive model containing a damage function is used. Compressibility and sideways spreading are ignored. Predictions of final sheet thickness given roll speed and diameter, gap and initial thickness
Australian & New Zealand Journal of Statistics, 2012
ABSTRACT There is an emerging need to advance linear mixed model technology to include variable s... more ABSTRACT There is an emerging need to advance linear mixed model technology to include variable selection methods that can simultaneously choose and estimate important effects from a potentially large number of covariates. However, the complex nature of variable selection has made it difficult for it to be incorporated into mixed models. In this paper we extend the well known class of penalties and show that they can be integrated succinctly into a linear mixed model setting. Under mild conditions, the estimator obtained from this mixed model penalised likelihood is shown to be consistent and asymptotically normally distributed. A simulation study reveals that the extended family of penalties achieves varying degrees of estimator shrinkage depending on the value of one of its parameters. The simulation study also shows there is a link between the number of false positives detected and the number of true coefficients when using the same penalty. This new mixed model variable selection (MMVS) technology was applied to a complex wheat quality data set to determine significant quantitative trait loci (QTL).
The quality of wheat (Triticum aestivum L.) for making bread is largely due to the strength and e... more The quality of wheat (Triticum aestivum L.) for making bread is largely due to the strength and extensibility of wheat dough, which in turn is due to the properties of polymeric glutenin. Polymeric glutenin consists of high- and low-molecular-weight glutenin protein subunits linked by disulphide bonds between cysteine residues. Glutenin subunits differ in their effects on dough mixing properties. The research presented here investigated the effect of a specific, recently discovered, glutenin subunit on dough mixing properties. This subunit, Bx7.1, is unusual in that it has a cysteine in its repetitive domain. With site-directed mutagenesis of the gene encoding Bx7.1, a guanine in the repetitive domain was replaced by an adenine, to provide a mutant gene encoding a subunit (MutBx7.1) in which the repetitive-domain cysteine was replaced by a tyrosine residue. Bx7.1, MutBx7.1 and other Bx-type glutenin subunits were heterologously expressed in Escherichia coli and purified. This made it possible to incorporate each individual subunit into wheat flour and evaluate the effect of the cysteine residue on dough properties. The Bx7.1 subunit affected dough mixing properties differently from the other subunits. These differences are due to the extra cysteine residue, which may interfere with glutenin polymerisation through cross-linkage within the Bx7.1 subunit, causing this subunit to act as a chain terminator.
Cereal Chem. 73(4):478-482 A device is described for measuring rheological properties of a dough ... more Cereal Chem. 73(4):478-482 A device is described for measuring rheological properties of a dough tional viscosity was of the order 105-106 Parsec when the elongation rate sheet with an Instron universal testing machine. A mathematical analysis varied from 10-3 to 1' sec1. Water addition affected the slope and the of the setup is presented, allowing the stresses, deformation (elongation), intercept
ABSTRACT As part of our studies on the mechanisms of bread staling, starch bread was used as a re... more ABSTRACT As part of our studies on the mechanisms of bread staling, starch bread was used as a research tool that enables us to gain insights into the individual contributions that starch and gluten have on staling. Reconstitution experiments have demonstrated that bread of equivalent specific loaf volume stales at the same rate irrespective of protein concentration, or type of protein. However, other properties of bread, such as specific loaf volume, may be altered by specifically changing the protein component in the flour.
The prediction of final sheet thickness after rolling of wheat flour dough is studied using an ap... more The prediction of final sheet thickness after rolling of wheat flour dough is studied using an approximate method that concentrates on the initial, intermediate and final material configurations. A newly proposed viscoelastic constitutive model containing a damage function is used. Compressibility and sideways spreading are ignored. Predictions of final sheet thickness given roll speed and diameter, gap and initial thickness
Australian & New Zealand Journal of Statistics, 2012
ABSTRACT There is an emerging need to advance linear mixed model technology to include variable s... more ABSTRACT There is an emerging need to advance linear mixed model technology to include variable selection methods that can simultaneously choose and estimate important effects from a potentially large number of covariates. However, the complex nature of variable selection has made it difficult for it to be incorporated into mixed models. In this paper we extend the well known class of penalties and show that they can be integrated succinctly into a linear mixed model setting. Under mild conditions, the estimator obtained from this mixed model penalised likelihood is shown to be consistent and asymptotically normally distributed. A simulation study reveals that the extended family of penalties achieves varying degrees of estimator shrinkage depending on the value of one of its parameters. The simulation study also shows there is a link between the number of false positives detected and the number of true coefficients when using the same penalty. This new mixed model variable selection (MMVS) technology was applied to a complex wheat quality data set to determine significant quantitative trait loci (QTL).
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