OSU Biochemistry and Molecular Biology

Dr. Patricia Rayas-Duarte




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 Research Tidbits

The prolamin proteins stored by the wheat plant in the kernels as a source of nitrogen for the development of a new plant is a marvel of polymeric (glutenin) and monomeric (gliadin) protein chains ready to form a very large polymer upon hydration and applied work.  Think in the work of mixing the dough in a yeasted bread to form a polymeric sponge that will soften during the fermentation process and then firm or set during the baking process.  The end result is the polymeric structure of yeasted bake bread possessing both elastic and viscous properties.

It is fascinating to study how a storage mass of prolamin protein chains relatively tightly folded in the wheat kernel ends up in a three dimensional sponge like network of gluten protein chains forming one of the largest polymers in nature.  The biopolymers formed the three dimensional chains that trap the CO2 and ethanol during fermentation expanding the dough. They also expand even more during the early stage of baking and end up forming the soft crumb as an interconnected system of cells and tunnels that form the bread crumb as well as a drier connected network that forms the bread crust.

All this is a result of the interconnected gluten biopolymers with specific material properties that allows them to be strong and resilient (elastic character) and expandable to flow (viscous character) as a result of an external disturbance.   The biopolymers that form the bread structure are viscoelastic at in all the stages of processing from dough to bread.  The balance of the elastic to viscous characters and their relationship to how the dough and bread behave it is the holy grail of making bread with specific characteristics, some desirable and others that definitively need to be improved, in order to produce baking goods with particular structures and for a particular customer expectations. 

We study the biochemical and physical (viscoelastic properties, surface hydrophobicity) properties of gluten biopolymers from hard red winter wheat that need to be improved and are of interest to the baking industry.  We collaborate with breeding efforts of improving the quality of wheat to achieve what the baking industry needs at the present time and anticipate future uses of wheat products.  We are creating new parameters and tools for understanding the structures of gluten biopolymers.  Specifically we strive for deciphering the physical tales of quite complicated biopolymers by interrogating their structure and biochemical components. 

For the study of material properties of gluten biopolymers, we study dough and isolated gluten systems.  We use fundamental rheological testing that measures the disturbance or deformation of the structure in the form of strain of the material under study as a response of an applied stress. We apply mechanical models to obtain quantitative information on the components of the biopolymers.

The information gained from these tests are related to the traditional empirical rheological testing that has been used since the 1940’s and have been successful in giving guidance to quality indicators of particular performance.  However, these empirical tests cannot be compared across each other and lack theoretical basis.

Strains vs. stress curves from fundamental tests are used to estimate key properties that reveal comparisons of the molecular structures formed by the gluten biopolymers.  These biopolymers have extensive polymorphism within the wheat cultivars and wild relatives.  This means that there are large number of individual proteins from different classes resulting in complex mixtures of homologous proteins varying in molecular mass and charge.  For example, individual proteins of low molecular weight glutenins (30-50 KDa) and gliadins (α-, ß-, γ- and ω-gliadins, 28 – 55 kDa) are difficult to isolate since their composition and molecular size is similar.  Up today, it has been difficult to prove the contribution of each particular type of gluten proteins with the present technology.   In the future, molecular genetic tools will be able to handle polyploid plants such as wheat with more efficacy.  For example, it will be possible to silence specific low molecular weight glutenin and gliadin proteins in hexaploid (six genomes in the cell) wheat, then direct evidence of the contribution of these proteins will be provided.  Thus, it will be possible to determine the underlying mechanism of the contributions of each gluten protein type. This will make possible to design the protein type and ratio that will produce a desired structure and functionality in specific products.   

We study three broad groups of gluten proteins known as high molecular glutenins, low molecular weight glutenins and gliadins.  We are interested in biochemical indicators such as protein-protein interactions, protein characteristics including charge to mass ratio, composition of groups separated by solubility and electrophoretic mobility, water soluble complex carbohydrates, antioxidant compounds found in hexaploid bread wheat.  Our interest also includes the study of compounds that will preserve the quality of frozen dough.  Our team and collaborators use modeling to understand mechanical properties of wheat kernels, gluten and dough.  We compare the coefficients of the pure elastic character, the retarded elastic behavior and the viscous flow to understand the quality character associated with each variety and breeding line. 

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