Agriculture Reference
In-Depth Information
Young 2006). Alternatively, hearth breads are not
confi ned in a pan during baking and are tradition-
ally baked on the hearth, or sole, of the oven.
Hearth breads generally have thicker and/or
crispier crusts than pan breads baked in lidded
pans, and have a wider range of crumb textures
from soft to very chewy. Crumb structures of
high-volume breads range from very fi ne-grained
for sponge-and-dough derived white sandwich
breads to more open structures such as those asso-
ciated with traditional French baguettes (Seibel
1998).
When assessing the general breadmaking suit-
ability of experimental breeder lines or large com-
mercial grain lots, dough rheological properties,
loaf volume, and crumb structure are generally
emphasized. However, loaf volume on its own
provides a valuable index of overall breadmaking
potential (Graybosch et al., 1999). Other impor-
tant factors are the form ratio (height-to-width
ratio) of hearth breads (Færgestad et al., 2000;
Sahlstrom et al., 2006), visual crumb characteris-
tics such as cell uniformity, size, shape, and cell-
wall thickness, and textural characteristics such as
moistness, elasticity, and smoothness (Collar et
al., 2005). Attributes like aroma, taste, and staling
(fi rming characteristics) can be assessed when
required. These latter factors are important to
consumers but are greatly affected by formulation
and process and therefore not necessarily key to
wheat “passing the test.”
For high-volume breads, loaf volume gener-
ally increases linearly with increasing fl our
protein content. This relationship, and its inter-
action with genotype, has been known for
decades; that is, for incremental increases in fl our
protein content, different wheat genotypes have
greater or lesser incremental increases in loaf
volume (Finney and Barmore 1948; Briggs et al.,
1969). Form ratio can also be affected. In hearth
breads at equivalent fl our protein content, weaker
and less elastic doughs from wheat genotypes
with glutenin subunits 2 + 12 (encoded by
Glu-D1a
) were shown to produce hearth breads
with signifi cantly lower form ratios (and lower
volumes) than breads made from genotypes
with glutenin subunits 5 + 10 (
Glu-D1d
)
(Tronsmo 2003). The biochemical basis of the
relationships between gluten composition and
baking quality has been reviewed elsewhere
(Gianibelli et al., 2001; Veraverbeke and Delcour
2002; Bekes et al., 2004) and is addressed in the
next chapter.
Steamed breads
A variant on the high-volume bread template is
steamed bread, which is most common in China
and other parts of eastern Asia. As with other
regional specialties, however, its popularity has
spread well beyond its place of origin. Steamed
bread is markedly different in appearance to baked
bread as a result of the absence of a brown crust,
having instead a white skin. Steaming maintains
the water activity of the bread surface well above
the level that allows for Maillard browning.
Steamed bread is traditionally made with a
sponge-and-dough process, although no-time
straight-dough systems are increasingly used
(Huang 1999). Leavening can be based on a sour-
dough starter or on yeast, or the steamed breads
can be chemically leavened.
The optimum quality characteristics of
steamed bread vary depending on geographical
origin; hence types of steamed bread are com-
monly categorized as northern, southern, and
Guandong styles. Respectively these are hard
and dense, softer and less dense, and very soft
and somewhat friable. The Guandong style
breads are noticeably different in formulation
with up to 10% sugar (fb) and 25% fat (fb), in
contrast to the lean formulae for the other styles
(Huang 1999). Specifi c steamed bread quality
attributes vary between styles, but common attri-
butes are the white color of both skin and crumb,
high volume and volume per unit weight (specifi c
volume), and a spread or form ratio of rounded
buns that show a bold aspect (i.e., width roughly
equal to height). A slumped aspect, where the
width is much greater than the height, is undesir-
able. All styles should also have a shiny, smooth,
and attractive external appearance (Huang et al.,
1993).
Flour quality for steamed bread varies with the
style being made. For northern style steamed
bread, hard wheat was preferred in one study
