Agriculture Reference
In-Depth Information
It provides the stretch and resistance to stretching
(i.e., elasticity) in dough. Wet gluten content is
determined by washing fl our or a ground wheat
sample with a saltwater solution to remove starch
from the sample. Gluten content is expressed as
a percentage on a 14% moisture basis. It also has
been used to estimate gluten quality or strength
by subjecting the wet gluten material to centrifu-
gal forces through a mesh. The percentage
remaining is called the gluten index and provides
an indication of gluten strength. Wet gluten is
used extensively as a product specifi cation and is
highly indicative of the protein content of wheat
fl our.
tency is an important indicator of value. A fl our
capable of holding more water as a dough can be
advantageous for certain products but is an abso-
lute necessity when formulating a bread product
from a specifi c wheat or fl our sample.
The farinograph measures water-holding
ability by fi rst defi ning optimum dough develop-
ment and then measuring the amount of water
required to reach that point. Hence farinograph
absorption is the amount of water needed to
center the farinograph curve on the 500-Braben-
der-unit line. Other measures such as the time it
takes for optimal dough formation (peak time),
the time a dough can be mixed before its consis-
tency weakens (stability time), and the degree of
dough softening during mixing (mixing tolerance
index) also are helpful in understanding how a
given grain sample will perform when mixed and
indicate, to some degree, the quality of gluten
formed (i.e., dough strength).
An extensograph determines dough extensibil-
ity and resistance to extension by measuring the
force required to stretch the dough with a hook
until it breaks. An extensograph curve indicates
resistance to initial stretching (resistance) and
resistance to breakage (extensibility) (Fig. 19.3).
The extensograph test results help millers and
bakers understand the gluten strength and bread-
making characteristics of a wheat or fl our sample.
It is also helpful in determining the effects of
Dough performance
Several instruments are used throughout wheat
commerce to assess developmental and extensional
properties of the dough. The farinograph mea-
sures and records the resistance of dough to mixing
with paddles. Results from the farinograph test
include water absorption, arrival time, stability
time, peak time, departure time, and mixing toler-
ance index. This is one of the most commonly
used fl our quality tests for bread wheat markets,
and a farinograph curve reveals several clues about
end-product quality (Fig. 19.2). Because water is
required to make dough, the amount of water
needed to develop a dough to its optimum consis-
Stability
600
500
500
400
400
300
300
200
200
Resistance to
Extension
100
100
minutes
Extensibility
0
5
10
15
20
0
20
40
60
80
100
120
140
Fig. 19.2 The farinograph curve helps the end user predict
mixing properties of a fl our sample. Stability, estimated from
the farinograph curve (Brabender units, BU, vs. minutes of
mixing time), is considered fi rst by bread makers as an indica-
tor of the dough's ability to maintain optimum consistency
while mixing. It is also another indicator of strength.
Millimeters Extensibility
Fig. 19.3 From an extensograph curve, the ratio of resis-
tance to extension and extensibility indicate the balance
between strength and the limit to stretch before breaking of
the dough.
 
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