Identification of Variety and Quality Type by Protein Analysis: Recommendation of Methods

Established and supported under the Australian Government’s Cooperative Research Centre Progra

Identification of wheat varieties and glutenin subunits: capillary electrophoresis and computer-assisted interpretation of results

Established and supported under the Australian Government’s Cooperative Research Centre Progra

DNA-based identification of Australian varieties of wheat and barley

Established and supported under the Australian Government’s Cooperative Research Centre Progra

Structure/function studies on systematically altered wheat flours

The gluten proteins have unique physico-chemical properties which enable use of the wheat flour to produce bread. This project was undertaken to study the chemistry of the different wheat storage proteins and to evaluate their contribution to the bread­making process in a controlled system where all parameters other than the varied one remained constant. In a systematic study of the functionality of different storage proteins, gluten and starch were separated from seven flour samples having a range of protein contents and functionality. Gliadin- and glutenin-rich fractions, high molecular weight glutenin subunits (HMW-GS), low molecular weight glutenin subunits (LMW­GS), HMW-GS 7 (x-type), HMW-GS 8 (y-type), and a range of gliadin types (a., P, y, co) were isolated. In addition HMW-GS 5 and 10 obtained by bacterial expression were also purified. Protein content, glutenin-to-gliadin ratio, HMW-GS-to-LMW-GS ratio, amounts of HMW-GS 7, 8, 5 and 10 and the different gliadin types were altered by blending these fractions into the test flours in calculated amounts using addition or incorporation. Mixing properties, extension-tester parameters and baking performance of composite flours were determined using small-scale techniques. New incorporation methods were developed to investigate the effects of glutenin subunits on extension and baking parameters. For the first time, basic principles of physics (basic rheological tests for elongation and viscosity) have been used to separate the effects of protein content and glutenin-gliadin ratio. The mixing time increased with increase in protein content, glutenin-to-gliadin ratio and HMW-GS-to-LMW-GS ratio. There was a general increase in peak resistance with increase in protein content, glutenin-to-gliadin ratio (in five out of seven flours) and HMW-GS-to-LMW-GS ratio. There was a decrease in resistance breakdown observed with increase in glutenin-to-gliadin ratio and HMW-GS-to-LMW-GS ratio. However resistance breakdown was different in samples as the protein content was increased. Three samples showed a general increase in resistance breakdown, two others showed an initial decrease in resistance breakdown followed by an increase and two samples showed a consistent decrease in resistance breakdown. The maximum resistance to extension increased with increase in protein content and glutenin-to-gliadin ratio. The maximum resistance to extension slightly increased with increase in HMW-GS-to-LMW-GS ratio (strongly in one cultivar, Hartog). Extensibility increased with protein content but decreased with increase in glutenin-to-gliadin ratio and HMW-GS-to-LMW­GS ratio (except in Osprey derivative). Increases in loaf height were observed with increase in protein content, glutenin-to-gliadin ratio and HMW-GS-to-LMW-GS ratio. Since this work confirmed that glutenin-to-gliadin ratio and HMW-GS-to-LMW-GS ratio had important effects on bread-making quality, there was potential to evaluate near infrared spectroscopy (NIR) as a tool for measuing the content of these four classes ofprotein non-destructively. Its use for measuring total protein content is very widespread and well established. NIR calibrations were developed for two blends of proteins, with 2308 nm distinguishing glutenin from gliadin and 2300 nm HMW-GS from LMW-GS. When a third component, starch, was added, however, the differences in spectra at these single wavelengths were no longer detectable. Nevertheless, the potential for non­destructive and indirect measurement of these two key ratios was demonstrated and its eventual application may depend on more sophisticated data processing. In incorporation studies of single and paired glutenin subunits, HMW-GS 5 + 10 gave a synergistic effect, increasing mixing time, maximum resistance to extension and loaf height as compared to HMW-GS 5 or 10 separately. However, HMW-GS 7 + 8 did not show any synergistic effects, and HMW-GS 7 incorporated separately had a higher mixing time, maximum resistance to extension and loaf height than those of HMW-GS 7 + 8 and HMW-GS 8. All gliadin fractions decreased mixing time, maximum resistance to extension and loaf height and increased resistance breakdown and extensibility. The various gliadin fractions showed differences in functional properties, with y-gliadin reducing the mixing time and maximum resistance to extension to the greatest extent, ro­gliadin contributing to the greatest reduction in loaf height and a + -gliadins having the least effect on reducing loaf height. Dough measurements determined by traditional Mixograph, Farinograph, Extensograph and Al veograph methods are empirical and not founded on parameters of basic physics. The application of methods of basic physics was also used in this study to differentiate the effect of protein content and glutenin-to-gliadin ratio on dough properties. Parmeters such as extension to rupture, tensile force, extensional viscosity, tensile stress (United Testing Machine), steady shear viscosity and time to peak viscosity (rheometer) were determined. The increase in protein content increased extension to rupture, tensile force, extensional viscosity and tensile stress but decreased steady shear viscosity. The increase in glutenin-to-gliadin ratio increased tensile force, extensional viscosity, tensile stress and steady shear viscosity but decreased extension to rupture. High correlations of extension to rupture and extensibility, tensile force and maximum resistance to extension (measured in traditional extension testing machine and United Testing Machine) confirmed the validity of traditional empirical measures of dough quality. The results obtained from the systematic study have allowed the separation of the effects of flour protein quantity and quality on functional properties

Wheat: grain-quality characteristics and management of quality requirements

Flour made from wheat is unique as a source of the dough-forming gluten proteins. These gluten proteins have the unique properties needed to make the many wheat-based foods, such as leavened breads, pasta, noodles, flat/pocket breads, steamed breads, biscuits, cakes, pastries and various food ingredients. Therefore wheat, an essential part of the diet of most of the world's population, is prominent in world trade. Its quality traits are the most critical of all the grains. The glutenin polypeptides (sub-units) make a substantial contribution to dough quality and their composition is used as a selection tool in breeding and in quality-based segregation of grain

Variety Identification of Australian Barley

Established and supported under the Australian Government’s Cooperative Research Centre Progra

Variety Identification of Australian Barley

Established and supported under the Australian Government’s Cooperative Research Centre Progra

Growth environment influences grain protein composition and dough functional properties in three Australian wheat cultivars

The objectives of this study were to assess how functional properties of proteins in whole meal wheat (Triticum aestivum L.) flour vary across different growth environments. Grain from three commercial, Australian hard, milling wheat cultivars was analysed from four growth locations in 2008, and from two of the corresponding cultivars and locations in 2009. The protein content of the grain, soluble and insoluble extractable protein fractions, swelling index of glutenin (SIG), glutenin to gliadin ratio (Glu:Gli), percent unextractable polymeric protein (%UPP), and dough properties including force at maximum resistance (Rmax) and extensibility (Ext) were measured. Based on analysis of variance of aggregated data for the cultivars, growth locations and seasons, growth environment factors made significant contributions to variability in the total grain protein, Glu:Gli ratio, %UPP, SIG, Rmax and Ext of the wheat flour. Variability of protein content of the soluble and insoluble extractable protein fractions was mostly due to genotype