Agriculture Reference
In-Depth Information
Transformation with genes that govern known
quality traits is also progressing. This approach
offers the prospect of effi cient introgression of
attractive genes without the laborious need for
repeated backcrossing (Shewry et al., 2003, 2006).
Furthermore, such introgression may cross the
normal boundaries of species and genus. The
insertion of specifi c glutenin genes into triticale
(Martinek et al., 2008) is an obvious approach to
improving the breadmaking potential of this
wheat-rye hybrid that has not lived up to hopes
for its baking quality.
Transgenic technologies may also be used to
manipulate the expression or overexpression of
specifi c storage-protein genes, thereby creating
novel dough properties (e.g., Rooke et al., 1999;
Butow et al., 2003). Such approaches might
provide “ingredient wheats” of extreme dough
strength that might be blended with low-protein
wheat with weak dough strength to provide ade-
quate dough quality, thus avoiding the need to
add vital dry gluten in baking. Alternatively,
wheat that has been manipulated to exhibit dough
of extreme extensibility might usefully blend with
otherwise unsuitable wheats to suit the needs of
biscuit (cookie) manufacture. On the other hand,
conventional breeding methods may be used to
incorporate the genes for storage proteins from
ancestral relatives into modern wheat. Such
manipulation has the potential to provide novel
properties for dough quality (e.g., Hassani et al.,
2008).
The contribution of the lipid component to
fl our quality should not be ignored when consid-
ering parameters to be used as a basis for selec-
tion in plant breeding programs, even though
protein composition appears to be the major
factor that determines fl our quality. Wheat has a
higher proportion of polar lipids than most other
cereal grains; this appears to be an important
factor contributing to its superior baking
performance.
Even in a basic bread-dough system, multiple
interactions occur among endogenous and/or
added components. The protein-starch com-
plexes, mediated by lipids, play important func-
tional roles. More studies are needed to understand
the association of lipids with dough proteins and
the manner by which gas-cell structure is stabi-
lized throughout dough mixing, proofi ng, and
baking. This information might prove applicable
in breeding programs which target intrinsic
baking qualities, thus obviating the need for
adding ingredients to wheat-based foods to
produce the required functional properties.
Whereas the range of amylose-amylopectin
ratio of wheat starch has been limited until
recently, new wheat genotypes are being devel-
oped that offer the full range of starch composi-
tion in this respect. The development of waxy
wheat (high amylopectin content) (Nakamura et
al., 1995) is further advanced than wheat with
high amylose content (Rahman et al., 2000). Both
new types of grain offer opportunities for innova-
tion in specialized and novel food products, espe-
cially in high-value snack foods.
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