Vol. 76, No. 3, 1999 389
Effect of Varying Protein Content and Glutenin-to-Gliadin Ratio
on the Functional Properties of Wheat Dough
1,2 P. W. Gras,
1,3,4 F. L. Stoddard,
1,2 and F. Bekes
Cereal Chem. 76(3):389–394
Gluten, starch, lipids, and water-soluble material were separated from
seven wheat samples with a range of protein contents and breadmaking qual-
ity. The isolated glutens were further partitioned into gliadin- and glutenin-
rich fractions using pH precipitation. Protein content and glutenin-to-
gliadin ratio were systematically altered by blending these fractions into
the original flours in calculated amounts. Mixing properties, extension-tester
parameters, and baking performance of composite flours were deter-
mined using small-scale techniques. Results of dough testing with blends
of constant glutenin-to-gliadin ratio showed increases in the mixing time,
mixograph peak resistance, maximum resistance to extension, exten-
sibility, and loaf volume as the protein content increased. At constant
protein content, increases in glutenin-to-gliadin ratio were associated with
increases in mixing time, mixograph peak resistance, maximum resis-
tance to extension, and loaf volume, and with decreases in extensibility.
Thus, total protein content and glutenin-to-gliadin ratio independently
affected dough and baking properties. The results have allowed the sep-
aration of the effects of flour protein quantity and composition on bread-
Several approaches are available to answer the question “what
constitutes the basis of baking quality in wheat flours?” One
approach is to measure compositional parameters such as the
amount of gluten, glutenin, or gliadin in a range of flours and to
search for correlations with baking performance. Another approach
is fractionation and reconstitution, where the functionality of each
of the separated flour components is evaluated by varying its
amount in a given flour or by interchanging separated fractions
between flours of different baking quality. The results establish
the roles of each component and show which are responsible for
differences in quality. In one of the earliest of these studies, loaf
volumes of flours from specific wheat types were correlated with
protein content (Aitken and Geddes 1934). Low protein flour,
enriched with dried gluten to give a range of protein contents,
showed loaf volumes and dough strengths that were highly
correlated with the levels of gluten protein (Aitken and Geddes
1938, 1939). When glutens prepared from different cultivars were
tested in a standardized starch-gluten test system, loaf volumes
were dependent on the source of gluten, that is, the properties of
the wheat glutens were cultivar-dependent (Harris and Sibbitt
1942). The results of other systematic fractionation and reconsti-
tution studies have implied that gluten protein was the component
mainly responsible for inherent differences in baking quality of
different wheat cultivars (Finney 1943).
More recently, it has also been shown that loaf volume depends
on the composition of the protein. Glutenins and gliadins together
represent ≈80% of the total protein in a typical wheat flour (Hoseney
et al 1969, Bietz and Wall 1975, Pritchard and Brock 1994, Tatham
and Shewry 1995). The contributions of gliadins and glutenins to
dough properties have been long been recognized, and it has been
suggested that the gliadins generally contribute to dough viscosity
and glutenins contribute to dough elasticity (Khatkar and Schofield
1997). It is the unique combination of dough viscosity and dough
elasticity that comprises the functional properties of dough. Major
effects on loaf quality have been demonstrated due to the high
molecular weight glutenin subunits (HMW-GS) present (Payne and
Lawrence 1983), the glutenin-to-gliadin ratio (Doekes et 1982,
MacRitchie 1987, Gupta et al 1992, Blumenthal et al 1994, Pechanek
et al 1997), the molecular weight distribution (MacRitchie 1987,
Gupta et al 1993), and overall protein content (MacRitchie 1992).
In each of these studies, the importance of one of these parameters
was established using sample sets where the other three parameters
were largely uncontrolled. In the present work, we have developed a
system where these other parameters can be kept constant.
In principle, experimental designs that incorporate the ability to
vary only one aspect of composition at a time while maintaining the
others as constants can be used to examine the relative importance
of any of the aspects of gluten composition. This article describes
the results of an improved approach that builds on the fractionation-
reconstitution work on glutenins and gliadins previously reported
(Hoseney et al 1969; MacRitchie 1985, 1987; Preston and Tipples
1980). This approach has been used to establish the relative effects
of protein content and glutenin-to-gliadin ratio by varying the
protein content and the glutenin-to-gliadin ratio independently.
MATERIALS AND METHODS
Wheat flours used in this study were derived from Australian
cultivars of diverse breadmaking quality. Cultivars Banks, Hartog,
Rosella, Sunbri, Yanac, and a derivative of Osprey containing the
1BL/1RS translocation (Osprey derivative) were obtained from
BRI Australia Ltd., North Ryde, NSW. A commercial bakers’ flour
blend (Queensland Bakers’) comprising cvs. Janz and Cunning-
ham was obtained from Weston Milling, Enfield, NSW.
Nonstarch lipids were extracted with chloroform (MacRitchie and
Gras 1973). Gluten, starch, and water-soluble material were sep-
arated from these defatted flours by manual washing followed by
freeze-drying (MacRitchie 1985). Glutenin- and gliadin-rich fractions
were isolated from each gluten using hydrochloric acid precip-
itation at pH 5.3 for gliadin and pH 3.9 for glutenin (MacRitchie
1985). These methods cause minimal disruption to the functionality
of the extracted components (MacRitchie 1985, Skerritt et al 1996).
The secalins extracted with the gliadins. The glutenin and gliadin
contents of each flour, gluten, glutenin- and gliadin-rich fractions
were determined in triplicate by size-exclusion HPLC (Batey et al
1991). For the purposes of this article, glutenin was defined as
Peak I and gliadin as Peak II as described by these authors.
The nitrogen contents of the flours, glutens, and glutenin- and
gliadin-rich fractions were determined by the Dumas total com-
bustion method using an elemental analyzer (CHN–1000, Leco Inc.,
St. Joseph, MI). Protein (%) was estimated as N × 5.7. The iden-
tity of HMW-GS was determined by SDS-polyacrylamide gel elec-
trophoresis (Laemmli 1970). The protein contents and the allelic
composition of the HMW-GS of the flours are given in Table I.
1Quality Wheat CRC Limited, Locked Bag No 1345, P.O. North Ryde, NSW
2CSIRO Plant Industry, GQRL, P.O. Box 7, North Ryde, NSW 1670 Australia.
3Plant Breeding Institute, Woolley Bldg A0, The University of Sydney, NSW
4Corresponding author. E-mail: firstname.lastname@example.org
Publication no. C-1999-0416-04R.
© 1999 American Association of Cereal Chemists, Inc.
390 CEREAL CHEMISTRY
Altering Protein Content and Glutenin-to-Gliadin Ratio
Blends of each of the base flours, with gluten and starch isolated
from that flour, were prepared. For each cultivar, blends of flour
and gluten isolated from it were prepared to have 110, 120, and
130% of the protein content in the base flour. Formulations con-
taining 70, 80, and 90% of the protein of the parent flour were
prepared by blending the flour with isolated starch. Each of the test
mixtures was prepared so the glutenin-to-gliadin ratio was iden-
tical to the value of the parent flour.
Gluten, glutenin, or gliadin prepared from the parent flour was
added to the flour to vary the glutenin-to-gliadin ratio, and protein
content was kept constant at 120% of that of the parent flour.
The glutenins and gliadins extracted from Banks, Hartog, Osprey
derivative, and Queensland Bakers’ flours were added to a base flour
(Queensland Bakers’ flour) to vary both the glutenin-to-gliadin
ratio and the subunit composition of the gliadin-glutenin. In this
experiment, the protein content was kept constant at 120% of the
base flour value.
All formulations were mixed on a 2-g mixograph (TMCO, Lincoln,
NE). Mixing trials were conducted using water absorptions esti-
mated by Approved Methods (AACC 1995) using the calculated
protein and moisture contents of the blend. The quantities of flour
and water thus estimated were scaled to provide a constant 3.5 g
of dough. Mixing was done in triplicate and the mean time to peak
dough development was calculated (Gras et al 1990). Parameters
recorded were mixing time (MT [sec]), mixograph peak resistance
(PR [AU]), and resistance breakdown (RB [%]).
Doughs for extension testing were mixed to peak dough devel-
opment in a 2-g mixograph using 3.5 g of dough. Extension was
done in duplicate on a microextension tester with a 19-mm gap and
6-mm hook operating at 1 cm/sec. Dough samples for extension
testing (1.7 g/test) were molded into cylinders (≈6 mm diameter)
with a prototype molder. They were then mounted on a sample carrier
and rested at 30°C and >90% rh for 45 min before extension testing
(Gras and Bekes 1996). Recordings of the dough resistance and the
sample carrier position were taken at 100 readings/sec and recorded
by a personal computer using LabTech Notebook software. Maximum
resistance to extension (Rmax [N]) and extension before rupture (cm)
were calculated using specially written software (Rath et al 1994).
Doughs were mixed to optimum development in the 2-g mixo-
graph. The formulation used flour including the added fraction
(100 parts), water (as calculated), salt (2 parts), fresh yeast (2.5 parts)
and improver (0.5 parts). Loaves were prepared from 2.4 g of the
resulting dough which was molded, rested for 20 min at 40°C,
remolded, proofed for 45 min at 40°C and 90% rh, and baked at
200°C for 17 min (Gras and Bekes 1996). Loaf height (LH) was
measured with vernier calipers. Baking tests were done in triplicate.
Statistical analyses were made by analysis of variance, analysis
of covariance, and regression analysis using the MSUSTAT pack-
age of computer programs (version 4.1) (Richard E. Lund, Montana
State University, Bozeman, MT) and SuperAnova v1.11 (Abacus
Concepts Inc., Berkeley, CA).
RESULTS AND DISCUSSION
Functionality of flour components isolated in this study has been
checked by reconstitution and, as previously observed (MacRitchie
1985, Skerritt et al 1996), replacement of gluten by approximate
mixtures of isolated gliadin and glutenin did not show significant
differences in any dough characteristics, indicating that functional
properties of the isolated components did not change significantly
during sample preparation. Separation of the effect of protein quantity
from the effect of glutenin-to-gliadin ratio required the isolated
gluten to have the same glutenin-to-gliadin ratio as the parent flour,
and within the limits of experimental error, this was found to be so
Protein Content, Allelic Composition of HMW-GS, and Glutenin-to-Gliadin Ratios of Seven Flours
Allelic Composition of HMW-GS
Ratio of HMW-GS
to LMW-GSSample Protein Content (%)1A1B1D Flour Gluten
LSD (P < 0.05)
Mixing, Extension, and Baking Parametersa for Mixtures of Queensland Bakers’ Flour and Isolated Glutenins and Gliadinsb
Sample Added to
Queensland Bakers’ Flour
LSD (P < 0.05)
aMixing time (MT), mixograph peak resistance (PR), resistance breakdown (RB), maximum resistance to extension (Rmax), extensibility (Ext), loaf height (LH).
bSource: Queensland Bakers’ (Q), Banks (B), Hartog (H), Osprey derviative (O).
cValues followed by the same letter are not significantly different (P < 0.05).
Vol. 76, No. 3, 1999 391
The variation of mixing time as a function of protein quantity was
very dependent on the cultivar and on the protein level (Fig. 1a).
In Queensland Bakers’, Sunbri, and Rosella, increasing the protein
content from a low value caused an increase in mixing time, but
there was less effect at the highest protein contents. In Osprey
derivative, Banks, and Yanac, increases in protein content had little
effect at low protein content, but at the higher levels (120 and
130% of parent flour) mixing time did increase. Hartog flour showed
much higher mixing time than the other flours.
Data points for all samples but Hartog showed a consistent
linear-positive relationship between protein and mixograph peak
resistance (Fig. 1b). For these six flours, the increase of mixo-
graph peak resistance with protein content was slightly curved, with
less effect seen at the highest protein contents. In Hartog, how-
ever, the effect of protein content on mixograph peak resistance was
small and reached its maximum at intermediate protein content.
This implies that there was cultivar-specific variation for mixo-
graph peak resistance superimposed on a more general relation-
ship between protein content and mixograph peak resistance.
The effect of protein content on resistance breakdown differed
among the flours (Fig. 1c). Banks, Osprey derivative, and Rosella
flours showed a general increase in resistance breakdown with
increase in protein content. Queensland Bakers’ and Sunbri showed
an initial decrease in resistance breakdown followed by an increase,
while Hartog and Yanac showed a consistent decrease in resis-
tance breakdown with increasing protein content.
Both the maximum resistance to extension and extensibility (Ext)
increased monotonically with increases in protein content (Fig. 1d
and e). The slope and intercept values for the linear approximation
of these relations varied from cultivar to cultivar, suggesting that
mean resistance and response to total protein content were both
The quality of loaves as measured by loaf height showed a sig-
nificant positive relationship with protein content for each sample
(Fig. 1f and Fig. 2), in agreement with previous observations on
loaf volume (Aitken and Geddes 1934, Harris and Sibbitt 1942,
Finney 1943, and many subsequent articles).
Variation in Glutenin-to-Gliadin Ratio at Constant Protein
Increases in the proportion of glutenin in the blend generally
increased mixing time (Fig. 3a), except in Sunbri at the highest
glutenin level where the decrease was not significant. Changes in
the glutenin-to-gliadin ratio had little or no effect on mixograph
peak resistance (Fig. 3b), which seemed to depend solely on the
cultivar and protein content, at least for the range in glutenin-to-
gliadin composition used in this study.
Increasing the glutenin-to-gliadin ratio mostly led to reduced re-
sistance breakdown (Fig. 3c) or increased tolerance to overmixing
or stability. The size of this change varied widely and significantly
from one cultivar to another (Fig. 3c). This may imply that
resistance breakdown is genetically determined. It may also re-
flect increased transfer of mixing energy, and thus resistance break-
Fig. 1. Mixing, extension and baking properties of seven wheat cultivars with protein content altered by the addition of gluten or starch from the cultivar
to provide 70, 80, 90, 100, 110, 120, and 130% of the protein in the parent flour. a) Mixing time; b) mixograph peak resistance; c) resistance breakdown;
d) maximum resistance to extension; e) extensibility; and f) loaf height. Banks (?), Hartog (?), Osprey derivative (?), Queensland Bakers’ (1),
Rosella (?), Sunbri (?), and Yanac (N).
392 CEREAL CHEMISTRY
down, in the stronger doughs because the height of the mixograph
curve represents a direct measure of the transfer of energy through
the dough. Increases in glutenin-to-gliadin ratio were associated with
increases in maximum resistance to extension in all cases (Fig. 3d).
The increase in resistance was consistent with the view that increases
in net average molecular weight of dough protein increases dough
strength (MacRitchie 1992). Increase in the glutenin-to-gliadin ratio
was generally associated with a decrease in extensibility (Fig. 3e),
Fig. 2. Microbaked loaves from wheat cultivar Banks with protein content altered by the addition of gluten or starch from the cultivar to provide 70, 80,
90, 100, 110, 120, and 130% of the protein in the parent flour.
Fig. 3. Mixing, extension, and baking properties of seven wheat cultivars with glutenin-to-gliadin ratio altered by adding gluten, glutenin, or gliadin. a) Mix-
ing time, b) mixograph peak resistance, c) resistance breakdown, d) maximum resistance to extension, e) extensibility, and f) loaf height. Values inside
bars represent glutenin-to-gliadin ratios.
Vol. 76, No. 3, 1999 393
with the exception of Hartog at the highest glutenin level where
the increase was not significant.
Increases in glutenin-to-gliadin ratio consistently showed signi-
ficant increases in loaf height (Fig. 3f and Fig. 4) as previously
reported for loaf volume (MacRitchie 1987). For the production of
pan bread, the most important quality characteristic of any flour is
its ability to produce bread of good volume. These results show
that increases in glutenin-to-gliadin ratio consistently improved flour
quality for this purpose, but if it is increased beyond the ranges
used in this experiment (0.58–1.55), it may reach a point where the
dough is too strong for breadmaking. From a practical viewpoint,
the resulting increases in mixing time might make such large
increases in glutenin proportion impractical.
Addition of Glutenins and Gliadins to a Base Flour
In this experiment, both the glutenin-to-gliadin ratio and the com-
position of the glutenin and the gliadin fractions were varied while
keeping the absolute amount of protein constant. In almost every
case, increases in the proportion of glutenin in the base flour
increased mixing time (Table II), as observed when glutenins from
the same flour were used. The extent of the change in mixing time
was largely dependent on the final glutenin-to-gliadin ratio. As
when gliadin and glutenin fractions were added to the parent
flours, the relation between mixing time and glutenin-to-gliadin
ratio was approximately linear, with the exception of the points
corresponding to glutenin from Osprey derivative.
Mixograph peak resistance was slightly but significantly reduced
when glutenin from Banks or Hartog was used, but increased when
glutenin from the Osprey derivative was used (Table II). It is
notable that this increase resulted from the addition of a fraction
that had a higher amount of HMW-GS than glutenins from Banks,
Hartog, and Queensland Bakers’ flour (Table I). Differences in
mixograph peak resistance resulting from admixture with gliadin
fractions were not statistically significant.
Increases in the proportion of gliadins increased the resistance
breakdown regardless of the gliadin source (Table II). The addition
of the glutenins resulted in no change in resistance breakdown,
except for Osprey derivative glutenin, which was atypical and
increased resistance breakdown. Thus, tolerance to overmixing or
stability decreased with decreased glutenin-to-gliadin ratio as ob-
served when the glutenin-to-gliadin ratio was altered with gliadin
from the base flour.
In every case (Table II), increases in the proportion of glutenins
in the test mixtures were negatively correlated with extensibility
(r = –0.69) and positively correlated with maximum resistance to
extension (r = 0.84). The trend line between maximum resistance
and glutenin-to-gliadin ratio was nonlinear, and the point associated
with Hartog glutenin appeared to be atypical. For extensibility, the
relation appeared to be linear, although the points due to Hartog
and Osprey derivative glutenins appeared atypical. The results
imply that in wheat breeding, emphasis on the proteins that will
increase the glutenin-to-gliadin ratio (or net molecular weight) at
some desired protein level will result in flours that have stronger
doughs but reduced extensibility.
Increases in glutenin contents at constant protein content were
also associated with increases in loaf height (Table II), as observed
when glutenin-to-gliadin ratio was altered with glutenin- and
gliadin-rich fractions of the same flour.
The use of glutenin- and gliadin-rich fractions from various
sources in one base flour (Queensland Bakers’) confirmed the trends
observed when glutenin- and gliadin-rich fractions were added to
the parent flours. In particular, the relationships between glutenin-
to-gliadin ratio and extensibility and maximum resistance to extension
were strongly confirmed. It was also apparent that protein content
and glutenin-to-gliadin ratio together were not sufficient to fully
describe the observed behavior. It is perhaps no coincidence that
those samples which behaved atypically in this study were those
where either the quantity (ratio of HMW-GS to LMW-GS in
Osprey derivative) or the quality (allelic composition of the HMW-
GS in Hartog) in the glutenin fraction were particularly different
from the remainder of the samples. It seems that both the mono-
meric and polymeric protein fractions have their own influence on
functional properties. Investigation of the effects of the composi-
tions of each of these monomeric and polymeric protein fractions
Fig. 4. Microbaked loaves from wheat cultivar Banks. 1) Parent flour; 2) flour plus gliadin; 3) flour plus gluten; 4) flour plus glutenin. Protein content of
2–4 equal to 120% of 1.
394 CEREAL CHEMISTRY Download full-text
is in progress using the concepts described above (systematically
changing one parameter at a time while keeping the remainder
The protein content and glutenin-to-gliadin ratio (a measure of
molecular weight distribution or protein size) have different roles
in determining the various dough and bread quality parameters.
Increases in the protein content at constant glutenin-to-gliadin
ratio increased mixing time, mixograph peak resistance, extensibility,
maximum resistance to extension, and loaf volume. Increases in
glutenin-to-gliadin ratio at fixed protein content increased mixing
time, mixograph peak resistance, maximum resistance to extension,
and loaf volume. Increases in glutenin-to-gliadin ratio decreased
resistance breakdown and extensibility. Differences in the quality
observed from flour to flour are thus determined, in part, by a
superimposition of the effects of protein content and glutenin-to-
gliadin ratio. These two effects are not sufficient to fully describe
the structure-function relationships in dough, and further work is
required to determine the effects of the chemical composition on
This project was funded by the Quality Wheat CRC, North Ryde,
NSW. We wish to thank Don Marshall for valuable discussion and
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[Received September 3, 1998. Accepted February 6, 1999.]