Agriculture Reference
In-Depth Information
by the test weight measurement. Two samples of
similar test weight could differ in TKW. Millers
view samples with higher TKW as having poten-
tially greater fl our yield.
undesirable. The falling number method uses
starch as the medium for determining enzyme
activity. The measurement device analyzes vis-
cosity by the resistance of a fl our and water paste
to a falling stir rod. Results are expressed in
seconds. A high falling number (e.g., more than
300 seconds) indicates minimal enzyme activity
and sound wheat quality. As enzyme activity
increases, the falling number value decreases and
soundness of wheat is questionable. A falling
number value less than 250 indicates that enzyme
activity is substantial and the wheat sample is
sprout-damaged regardless of any detectable
visible damage.
Falling number is important to millers because
enzyme activity affects baked product quality.
Too much enzyme activity means too much sugar
is present and too little starch is available to aid
in product support structure. This can result in
very sticky dough during processing and poor
texture in fi nished products. There is no remedy
for wheat with excessive enzyme activity. Low
enzyme activity can be adjusted by adding addi-
tional enzymes to fl our prior to baking. Once
present, enzymes cannot be removed from wheat
or fl our, making low falling number a serious
problem for millers and bakers.
Grain hardness
Class descriptions specify wheat as hard or soft,
but although this general view of hardness is
understood in trade and has long been used for
classifying wheat in the cultivar development
process, more defi nitive hardness measures are
necessary. Several methods exist for measuring
and differentiating wheat hardness. One parame-
ter commonly used to describe hardness within
a class is the particle size index (PSI). The PSI
is expressed as a percentage of fl our produced
by grinding a sample on a specifi c laboratory
mill. A softer wheat produces more fl our as a
percentage of the original wheat sample. The
SKCS measures the force required to crush a
kernel of wheat. A softer wheat requires less
crushing force than a harder wheat. The results
are presented as a mean value for 300 kernels with
a standard deviation.
Millers are interested in hardness not because
this characteristic can help determine soundness
of the crop but because knowledge of the hardness
level may reveal possible processing changes that
might be required. For example, the amount of
time required for water to penetrate into the
kernel increases with wheat hardness. This is not
a concern when a miller purchases consistently
within a class from the same area. However, if a
miller purchased HRS wheat, a very hard class
of wheat, as a replacement for HRW wheat,
a medium hard class of wheat, the time required
for moisture penetration would increase
signifi cantly.
Starch viscosity
Viscosity analysis is a measure of starch proper-
ties and enzyme activity resulting from sprouting
wheat and typically is performed by measuring
resistance of fl our and water slurries to a stirring
action. When the slurry is heated, starch granules
absorb water, thickening the mixture into a paste-
like consistency. A thicker slurry has greater
resistance to the stirring action, which indicates
low enzyme activity and indicates water-holding
capacity of the starch. Viscosity analysis in the
absence of high enzyme activity is important in
products such as cakes, pancakes or batters, and
coatings.
Falling number
Falling number is an indication of the level of α-
amylase enzyme activity in grain. Enzyme activity
precedes the sprouting process in wheat and is
undetectable under current grading systems,
which recognize only visible sprout damage as
Wet gluten content
Gluten is the primary protein component of the
structure formed when water and fl our are mixed.
