Writing Australian and Chinese wheats on floor protein content,

Writing
a review on the interaction between Protein content, Quality and Dough
properties in measuring the Quality of Chinese Steamed Bread

Summary

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China is the biggest producer and exporter of wheat
in the world among other countries. Wheat in china has varied uses and among
these is the production of steamed bread1.
Across the globe, most markets especially in Asia, steamed bread is popular comprising
over 40% total annual consumption 2
3.
There are two major types of steamed breads; The Southern style and the
Northern style2,
4.
In china, steamed bread has diverse tastes due to various assorted variables
incorporated in mixing and formulation procedures2.
The Northern and Southern styles have also different flour qualities which
exist in them2,5
Northern wheat need to be genetically improved to improve the quality of
Chinese steamed bread. Food processors researched the attributes of an
increased steamed bread quality with many cultivars of wheat2,5.
Surprisingly, startling outcomes were recorded. In studies carried out between Australian
and Chinese wheats on floor protein content, Australian wheats indicated a very
big difference and it negatively correlated with quality of steamed bread6.
The other study indicated a positive correlation where the protein content of
less than 10% was found5.
Steamed bread quality is greatly affected by the quality of the protein there
by directly giving a bearing of the strength of the dough5.
High levels of protein were found in Canadian and Chinese wheats and these
correlated with quality of steamed bread. This was also evidenced in soft wheat
which contain a sizeable amount of protein which improve the softness of
steamed bread and able to retain carbon dioxide during fermentation. Soft wheat
is also believed to contain more friable particles hence less heat energy is
required during milling7.
Few if not any of these characteristics were found in hard wheat8, 9.

 Differences
in quality of steamed bread differs from processing processes used and method
of observation used. Further, formulation, milling and evaluation procedure applied
also plays a key role in steamed bread quality 5, 6, 10, 11. In the past, Chinese wheats
showed a reduction in strength of dough even though protein content was high
than with wheat from other countries 6, 7, 11. Agronomic breeding practices
maybe have contributed to a reduction in dough quality due to the emerging
demand from the ever rising population. Improvement of quality was ignored as
more emphasis was shifted towards disease resistance, desirable yields and
early maturity11.
This of course produced disease resistant crops due to high percentage of 1B/1B
translocation wheats but this practice weakened dough stickiness 12, 13. 
Breeders were not concerned with end use quality. Improvement of wheat
quality began around 80s when Chinese breeders shifted their focus to end use
quality improvement of wheat7, 11. It is however a gradual process for
the quality can be improved. Quality can be improved by the use of Recombinant
substitution lines between different cultivars to produce desirable amount of
friabilin and softness as shown by Particle Size Index PSI of Buhler milled
floors14.

Introduction

Australia used to be the biggest exporter of wheat
to china. It was because over the emerging demand and forces in the market.  This can bring a lot of interests on the
similarities and differences between Australian and Chinese wheats and the end
use quality. Australian wheats from recent studies showed an increased dough
strength which could retain gases 2, 6, 7. Due to ever increasing rates of
new cultivars, information will be scarce. Various cultivars from China and
Australia were chosen and grown in same environment across Australia. To obtain
the difference, comparison was on flour and the quality of steamed bread
between Chinese and Australian varieties. Importers and exporters need the
information as the guiding principles for agronomists to determine the end use
quality of the wheat. The most critical components of gluten viscoelastic
property is the quality and quantity of High Molecular Weight-Gluten Subunits
(HMW-GS). HMW glutenin played an important role in baking steamed bread4, 15.

Baking quality is also a determinant of HMW-GS content
as it positively affect quality of Chinese steamed bread4, 15. The requirements for Chinese
steamed bread and pan bread are different. Therefore it is of great interest to
take a close look on HMW glutenin quantity and steamed bread quality8.  In a study carried out by J. Zhu, S. Huang,
K. Khan and L. O’Brien on Relationship of Protein Quantity, Quality and Dough Properties
with Chinese Steamed Bread Quality 1,
they found out that varying wheats from Australia were randomly selected which
were possessing various biotypes differing only on quantity of High Molecular
Weight-Gluten Subunits (HMW-GS). The difference in biotypes provided a very
important tool in an attempt to investigate the correlation between High
Molecular Weight-Gluten Subunits quantity and end use requirements and other
variable effect components of protein content were eliminated.

Furthermore, processing methods also influenced the
distributional content and granularity of glutenin polymers7, 16. 
In a study research carried out, it was found SDS insoluble glutenin
determined more the strength of the dough as compared to total polymeric
proteins17.
SDS-PAGE was used for showing size distribution of the SDS soluble glutenins18, 19 and it had an impact on the
quality of the bread1-3, 8, 19-25. As researchers were more focused
on improvement of yield, disease resistance and maturity, glutenin and quality
of Chinese steamed bread was not taken into consideration as this was also affected
by unavailability of adequate information2.
However because of limited information, researchers began to carry out
experiments comparing protein content in flour and composition of HMW-GS on
Chinese steamed bread quality1.
HMW-GS and Low Molecular Weight Gluten Subunits (LMW-GS) subunits are the two
main constituents of glutenin and these are linked by Glu-1 and Glu-3 loci
respectively. It is in this regard that Chinese breeders developed the
revelation to examine the possible measures of improving quality of Chinese
steamed bread. Extensive agronomic research was employed.

 

Materials and Methods

Wheat and flour sample

In a study carried out by J. Zhu, S. Huang, K. Khan
and L. O’Brien on Relationship of Protein Quantity, Quality and Dough Properties
with Chinese Steamed Bread Quality, 11 Australian cultivars were used which
are; HMR-H31, Batavia, Tasman, Ouyen, Matong, Machete, Vulcan, Oxley, Eradu,
Spear And Sunvale. Among the Chinese wheat cultivars used were; Zhong 33,
Linfen 7203, Yangmai 5, Jingdong6, Jimai 26 and Limai 151, 2, 22. Randomized split block design was
used. Some  plots were deficient of
nitrogen per hectare basis and in other plots nitrogen was introduced 200kg/ha1, 3. The research was carried out in
1996 in Narrabri, Australia1.
The correlation between HMW glutenin subunit and quantity and quality of
Chinese steamed bread was examined by the use of different biotypes with
cultivars which were differing in HMW glutenin subunit. Milling of grains was
done by a Brabender Quadrumat Sr. mill which was obtained in Germany.3

 

Source: Relationship of Protein Quantity, Quality
and Dough Properties with   Chinese
Steamed Bread Quality

 Chinese
steamed bread quality

Quality test

In J. Zhu, S. Huang, K. Khan and L. O’Brien’s study
on Relationship of Protein Quantity, Quality and Dough Properties with Chinese
Steamed Bread Quality1,
testing of four protein quantity was done according to the method of AACC39-11
using Near-Infrared Reflectance (NIR)26
. Farinograph tests were also employed to test dough properties with 10g and
this took place at Narrabri NSW Australia at Plant Breeding Institute. In an experiment
conducted by Ping ping Zhao, for protein content was also determined by the
Near-Infrared Reflectance spectroscopy method (AACC 39-11.01) using a Parten DA
70027.
Ping ping Zhao and co- workers4
also used a 10g mixograph to measure the mixing peak time of dough as well as
calculation of the interaction of water absorption and dough using mixograph
curve27.(AACC54-40.02)
J Zhu and co-workers prepared Northern Styles steamed breads using known
procedures for preparation of steamed breads8.
Quality makers used were dough elasticity, color, texture, spread ratio, crumb
structure, volume, weight, height and width. Each marker was expressed as a
percentage. Rapeseed displacement was used to evaluate the volume of steamed
bread.

 

 

Results and discussion

Differences in quality of steamed bread between
Chinese and Australian wheats

Both Australian and Chinese wheats exhibited a great
difference in quality of Chinese steamed bread as evidenced in (Table1&2).
Australian varieties showed an increased protein quantity and high scores were
evidenced on volume, weight, spread ratio, color, structure and quality in
eating as compared to Chinese steamed bread quality Table1). At highly extreme
protein content between Australian and Chinese wheats, two similarities were
seen, thus shininess and smooth texture. Protein quantity in both wheats were
found to be at par and this brings the notion that the divergence in quality of
steamed breads may be as a result of protein quality in the cultivars used
(Table 3).1, 5, 21

Table 2

Source: Relationship of Protein Quantity, Quality
and Dough Properties with   Chinese
Steamed Bread Quality

 Australian
wheats had poor scores on shininess at low protein content while Chinese wheats
exhibited exorbitant scores at low protein content (volume, with, spread
ration, color, etc…) and negative scores being recorded on shininess
(Table1). At low protein quantity, both cultivars did not correlate especially
on chewiness and smoothness1.
This may be due to the additives added like yeasts, gluten matrix dilution and
dough viscosity in relation to absorption21. In their study
they also discovered that differences in eating quality, color, texture, and
sensory assessment was due to addition of 3% Soy Protein Isolate (SPI)21. Quality of
Chinese wheats (Jimai 26, Lumai15 and Jingdong) was also lowered by dough stickiness
while Australian varieties did not exhibit any stickiness (Table1). Breeding
procedure in chine could be the major contributing factor for the dough
stickiness

Lower protein content seemed to be of no influence
on dough stickiness in making steamed bread for example Jamai 261,3.

Zhong 33, Yangmai5 and Linfen 7203 had an average
score of 76.8 (Table 2) which is the best score, scored by those Australian varieties
of 73.1 of all 11 wheats used (Table 1)1.
These results were recorded at high protein level.  At lower protein quantity, three Chinese
varieties which are Zhong 33, Yangmai 5 and Linfen 7203 recorded an average
score of 51.61.(Table
2) of which the average score of Australia counterparts was as low as 43.9
(table 1) (P?0.05). With these outcomes, it can partially be concluded that
dough stickiness in Chinese wheats contributed greatly to the quality of
Chinese steamed bread than Australian wheats.

Farinograph highlighted a big gap between Australian
and Chinese wheats on dough viscosity 1, 21, 24, 3(Table3).
Australian wheats are also characterized by increased stability and needed more
development time on dough (DDT)1.
At low protein content, dough development time in both Australian and Chinese
wheats were the same, no variables were recorded. Weak dough stability was recorded
in Chinese wheats than Australian wheats.

Correlation between protein quantity, dough stickiness
and Chinese steamed bread quality

Australian and Chinese wheats exhibited an
improvement in protein quantity on the steamed quality markers but however
shininess and spread ratio differed (Table 1). As protein quantity positively
accelerated, spread ratio decreased reflecting a negative effect of protein on
dough stickiness.

Source: Relationship of Protein Quantity, Quality
and Dough Properties with   Chinese
Steamed Bread Quality

 

The increase in protein content hence is believed to
affect the size, structure and volume. A reduction in shininess (outlook
appearance) on Australian wheats was evidenced. Chinese wheats showed no
variation with increased protein content1.
No significant change was recorded on smoothness on Chinese wheats but was
evidenced in Australian wheats. Protein quantity in flour had an overall
influence on quality of Chinese steamed bread1.
This show that protein quantity in flour play a pivotal role in bringing about
quality of chines steamed bread 1, 22-24.

Australian wheats showed an increased protein
content and the proteins retain or trap gas particles during leavening there by
increasing quality of steamed bread. The total score in Australian wheats which
were subjected to nitrogen treatment were high (Table 1). Dough stickiness also
believed to be a contributing factor to these worrying divergences.

 

 

Chinese
steamed bread quality

Source: Relationship of Protein Quantity, Quality
and Dough Properties with   Chinese
Steamed Bread Quality

 

Table 4 above show some correlation parameters in
Chinese steamed bread on Chinese and Australian wheats. Quality markers thus
volume, smoothness, structure, eating quality negatively correlated at 200kg/ha
when nitrogen was added1.
Farinograph also recorded a negative stability time1.  These results indicate that the increase in
protein may cause or bring about good quality to steamed bread. Positive
correlations were seen with increased flour protein. In 0kg/ha treatments, no
correlation was recorded between Farinograph stability time on Chinese steamed
bread quality among Australian wheats variety showed an increased flour protein
as evidenced by color, structure and total score (Table 4). On nitrogen treated
samples for Chinese wheats, Farinograph stability time positively and
significantly correlated indicating an increase in structure, chewiness, color,
volume, width and total score while no variation was witnessed on quality of
Chinese steamed bread (Table 4). The differences obtained in correlations
between Australian wheat flour protein and Chinese wheat protein flour might
not only due to variations in protein quantity but also different countries
(Australia and China)1, 3

Chinese wheats are characterized with sticky and too
viscous dough properties and development time on Farinograph dough even though
protein content in Australian and Chinese wheats was the same2, 3, 22, 24, 25, 28. With these data, researchers now
need to shift their focus towards dough improvement since it will also affect
quality of Chinese steamed bread1.
Size distribution of Glutenin polymers and quantity of protein are believed to
be the pillars of the differences between Australian and Chinese dough
structure. The outcome of each results may pave way for breeders to improve
Chinese breeders1.

Protein traits and Chinese steamed bread

Source: Relationship of Protein Quantity, Quality
and Dough Properties with   Chinese
Steamed Bread Quality

 

The data on table 5 shows that Australian cultivar,
Wariginal at HMW exhibited an increase in quality of Chinese steamed bread with
a total score of 44.2c1.
At LMW sub units, no difference was recorded. Australian wheats are known for
improvement in Chinese steamed quality but amongst the cultivars used in J.
Zhu, S. Huang’s experiment, they all displayed different results which may then
raise the idea that not only protein quantity bring a bearing in the quality of
Chinese steamed bread. This can be attributed to puroindolines or granularity
of glutenin polymers with the grains29. This mishap
maybe overcomed during milling where the grains needs to be milled to a fine
powder. Protein is believed to be centralized on one part of the grain
therefore milling methods must ensure even distribution of protein in the
flour. The differences in biotypes between Waginal, Lance and Schomburgk can be
as a result of drying methods used as these have an impact on protein
functionality7.
Protein quality in Lance and Schomburgk was believed not functional maybe due
to drying procedures incorporated, thus gamma irradiation and or microwave
heating.7

Dough stickiness

In the study carried out by J. Zhu, S Huang, etc..,
nothing on grain texture was mentioned. Huang et al 5purported
that for increased quality, hard grain texture is much preferred for Chinese
steamed bread7.
In another study carried out by Addo et al compared dough properties in making
pan bread and the outcome was that hard wheats perform better in dough
properties8.
They further concluded that wheat varieties are called soft or weak wheats if
gluten content is low and hard or strong wheats if gluten content is high7, 8. 
This will determine end use quality. 
Some studies outlined that medium sized gluten is much preferred for
almost all kinds of bread because of good malleability property and increased
raising of the bread which will retain gases8.
Some scholars also argued that dough properties may be due to environmental
factors like location, soil type not necessarily protein quantity. So other
variables need to be taken into consideration when trying to site the properties
of dough in Chinese and Australian wheat. Dough stickiness maybe affected by
non-endosperm components which may dilute the functional components 5, 6, 8, 11.

Conclusions

Quality of Chinese steamed bread is dependent on a
number of factors. The major factor among these is protein quantity and
quality. Protein content give the quality to Chinese steamed bread as seen in
the research carried out by J. Zhu, S. Huang that protein content enable dough
strength, increase in volume, color, size and chewiness among other variables.
Australian wheats have good dough property as compared to Chinese wheats.
Chinese wheats have poor dough properties and this weakened the quality of
Chinese steamed bread using Chinese wheats. 
Dough stickiness was one of the major contributing factors on
deterioration of Chinese steamed bread quality in Chinese wheats. Recombinant
substitution lines need to be employed to improve the quality of wheats in
china.

Breeders need to shift their focus on the
improvement of protein content in Chinese wheats to increase the quality of
Chinese steamed bread. Genetic engineering need to be effectively launched to
curb these worrying differences between Australian wheat and Chinese wheat varieties
for improved Chinese steamed bread quality. 

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