S. Uthayakumaran

Basic Rheology of Bread Dough with Modified Protein Content and Glutenin-to-Gliadin Ratios

ABSTRACT The uniaxial elongational and shear rheology of doughs varying in either the protein content or glutenin-to-gliadin ratio were investigated. Increasing the protein content at constant glutenin-to-gliadin ratio increased the strain-hardening properties of the dough, as shown by increasing elongational rupture viscosity and rupture stress. Glutenin and gliadin had a more complex effect on the elongational properties of the dough. Increased levels of glutenin increased the rupture viscosity but lowered the rupture strain, while elevated gliadin levels lowered the rupture viscosity but increased the rupture strain. These observations provide rheological support for the widely inferred role of gliadin and glutenin in shaping bread dough rheology, namely that gliadin contributes the flow properties, and glutenin contributes the elastic or strength properties. The shear and elongational properties of the doughs were quite different, reflecting the dissimilar natures of these two types of flow. Increasin...

Effects of Incorporated Glutenins on Functional Properties of Wheat Dough

ABSTRACT The development of reduction-oxidation methods to open the native gluten polymer, incorporate monomers, and repolymerize the modified polymer, has allowed new types of investigation of the effects of glutenin subunits on dough characters. These methods were used to incorporate bulk high molecular weight glutenin subunits (HMW-GS) and bulk low molecular weight glutenin subunits (LMW-GS) from four cultivars into the parent flours to modify the HMW-GS-to-LMW-GS ratio. In addition, the glutenins from the four cultivars were added to a single base flour of differing glutenin subunit composition. Finally, HMW-GS 7, 8, 5, and 10 were incorporated singly and in pairs into two base flours. The mixing time, peak resistance, maximum resistance to extension, and loaf height increased with increases in HMW-GS-to-LMW-GS ratio. There was a decrease in resistance breakdown observed with increase in HMW-GS-to-LMW-GS ratio. The maximum resistance to extension slightly increased with increases in HMW-GS-to-LMW-GS r...

Effects of Gliadin Fractions on Functional Properties of Wheat Dough Depending on Molecular Size and Hydrophobicity

ABSTRACT The effects of α- + β-, γ-, ω- and total gliadins on mixing, extension baking, and techno-functional properties of doughs from hard and soft flours were measured using small-scale techniques. The addition of all gliadin fractions resulted in decreased mixing time, peak resistance, maximum resistance to extension, and loaf height, and in increased resistance breakdown and extensibility. The various gliadin fractions showed differences in functional properties, with γ-gliadin reducing the mixing time and maximum resistance to extension to the greatest extent, ω-gliadin contributing to the greatest reduction in loaf height, and α- + β-gliadins having the least effect on reducing loaf height. The effects of gliadin fractions on loaf height were correlated with molecular mass, and effects on mixing time, maximum resistance to extension, and extensibility were correlated with hydrophobicity.

Synergistic and Additive Effects of Three High Molecular Weight Glutenin Subunit Loci. II. Effects on Wheat Dough Functionality and End-Use Quality

ABSTRACT Understanding the relationship between basic and applied rheological parameters and the contribution of wheat flour protein content and composition in defining these parameters requires information on the roles of individual flour protein components. The high molecular weight glutenin subunit (HMW-GS) proteins are major contributors to dough strength and stability. This study focused on eight homozygous wheat lines derived from the bread wheat cvs. Olympic and Gabo with systematic deletions at each of three HMW-GS encoding gene loci, Glu-A1, Glu-B1, and Glu-D1. Flour protein levels were adjusted to a constant 9% by adding starch. Functionality of the flours was characterized by small-scale methods (2-g mixograph, microextension tester). End-use quality was evaluated by 2-g microbaking and 10-g noodle-making procedures. In this sample set, the Glu-D1 HMW-GS (5+10) made a significantly larger contribution to dough properties than HMW-GS coded by Glu-B1 (17+18), while subunit 1 coded by Glu-A1 made ...

Synergistic and Additive Effects of Three High Molecular Weight Glutenin Subunit Loci. I. Effects on Wheat Dough Rheology

ABSTRACT The high molecular weight glutenin subunits (HMW-GS) play an important role in governing the functional properties of wheat dough. To understand the role of HMW-GS in defining the basic and applied rheological parameters and end-use quality of wheat dough, it is essential to conduct a systematic study where the effect of different HMW-GS are determined. This study focuses on the effect of HMW-GS on basic rheological properties. Eight wheat lines derived from cvs. Olympic and Gabo were used in this study. One line contained HMW-GS coded by all three loci, three lines were each null at one of the loci, three lines were null at two of the loci and one line null at all three loci. The flour protein level of all samples was adjusted to a constant 9% by adding starch. In another set of experiments, in addition to the flour protein content being held at 9%, the glutenin-to-gliadin ratio was maintained at 0.62 by adding gliadin. Rheological properties such as elongational, dynamic, and shear viscometric ...

Optimized Methods for Incorporating Glutenin Subunits into Wheat Dough for Extension and Baking Studies

ABSTRACT In order to study the functional properties of glutenin subunits added to a dough, they must be incorporated into the glutenin polymer. This requires partial reduction to open up the polymer, followed by oxidation to incorporate the added monomer into the polymer. Existing methods for incorporating glutenin subunits were suitable only for studies on mixing properties and needed to be modified for use in studies on extension and baking. A range of concentrations and of reaction times was therefore tested for both the reductant and the oxidant. In addition, mixing time as well as relaxation time before extension were varied. Extension curves and loaf heights were used to evaluate the treatments. Optimum conditions were developed that provided extension curves of normal dimensions but with altered shape. The conditions were reduction with 0.2 mg/mL of dithiothreitol (DTT) solution for 1 min followed by oxidation with 5 mg/mL of KIO3 solution, then mixing the dough to 70% of the peak dough developmen...

Wheat: characteristics and quality requirements.

Abstract: Wheat is unique as a source of the gluten proteins that alone have the dough-forming properties needed to make the variety of foods that rely on the rheology of dough, namely, 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 (subunits) make a substantial contribution to the wheat quality and their composition is used extensively as a selection tool in breeding and in quality-based segregation of grain.

Growth Environment Influences Grain Protein Composition and Dough Functional Properties in Three Australian Wheat Cultivars

ABSTRACT 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 analyzed 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 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 extensibility of the wheat flour. Variability of protein content of the soluble and insoluble extractable protein...

The effect of pre-test deformation on dough rheology

We show that the strain involved in forming a dough specimen before testing will often radically alter the measured rheological properties in shear and in elongation if these pre-strains are greater than about 0.5 (Hencky strain). It is shown that this may be accounted for by changing the G(1) value used in the damage function model to a relevant value.

Relationships between traditional and fundamental dough-testing methods

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.