Agriculture Reference
In-Depth Information
when milled. Nonvitreous kernels tend to mill to
fi nes, or milled particles which pass a US number
100 sieve (150 μm). Durum fl our, to distinguish
it from semolina, is defi ned as the material passing
a US number 70 (212 μm) sieve (Donnelly and
Ponte 2000). Sissons et al. (2000), using a single-
kernel characterization system (SKCS 4100,
Perten Instruments, Huddinge Sweden) to
predict vitreousness, showed a weak but positive
correlation between vitreousness and semolina
yield.
Grain protein content should be high enough
to produce semolina of >11% protein (Sissons
2004). The resultant semolina should be bright,
yellow or amber in color, and free, as far as pos-
sible, from visible specks of bran. Semolina should
have a uniform particle-size distribution, which
allows even hydration of all particles during
mixing. The protein content of semolina is widely
considered the primary factor infl uencing pasta
cooking and eating qualities. However, the semo-
lina should also make a relatively strong dough.
Strong gluten semolina has been associated with
better cooking and eating qualities and allows
better fl exibility with regard to drying regimes
(Cubadda et al., 2007).
The key quality attributes of pasta are appear-
ance, cooking quality, and cooked texture. Dried
pasta products should have a bright, clear yellow
or amber coloration (yellowness CIE b* value
>56 in spaghetti dried at 70 ºC), and the dried
product should be free of visible cracking or
checking (Sissons 2004). Cooking and texture
quality factors include fi rmness, lack of surface
disintegration, and lack of stickiness (Troccoli et
al., 2000). The extent of surface disintegration
can be conveniently estimated by directly mea-
suring the solids-loss in the cooking water or by
colorimetric measurement of the amylose con-
tent in the cooking water (Matsuo et al., 1992).
Cooking losses have been shown to decrease with
increasing semolina protein content (Malcolm-
son et al., 1993). Firmness can be assessed by
sensory analysis or by instrumentation. Attempts
have been made to standardize the instrumental
assessment of pasta fi rmness (Sissons et al.,
2008).
COMPOSITIONAL ANALYSIS AND
GRAIN TESTING
Moisture
Moisture is a fundamentally important constitu-
ent of grain, fl our, and fi nished end products.
Major needs are satisfi ed by knowing moisture
content—for example, whether grain can be
stored without being susceptible to mold growth
or how much tempering water to add to grain
before milling. The performance of subsequent
analyses on an equivalent-solids basis, and the
reporting of other compositional analyses at con-
stant moisture, is predicated on accurate knowl-
edge of moisture content. Indeed knowledge of
the amount of water already present in the mate-
rial is paramount, since so many aspects of fl our
and dough technology require measured but vari-
able water additions.
Moisture can be measured in a variety of ways
but derivative methods need to refer back to the
basic air-oven method: drying the sample in an
oven at a specifi ed high temperature (e.g., 130 ºC)
and measuring weight loss as a proportion of the
initial weight. One-stage drying is used for mate-
rials
13% moisture and two-stage drying for
samples
<
13% (AACC method 44-15A, AACC
2000). Moisture can also be estimated by dielec-
tric meter (capacitance) or by near-infrared
spectroscopy (NIRS), or by conductance in the
Perten SKCS 4100. Water is a strong absorber
of near-infrared energy and the higher the
moisture content, the more near-infrared energy
is absorbed (Caddick 2007). Hence NIRS is
well suited to the measurement of moisture
content.
Moisture content is obviously critical.
However, moisture may not be distributed evenly
in a kernel or end-product structure, and exciting
advances in monitoring moisture distribution
have arisen, particularly with the development of
magnetic resonance imaging (MRI) techniques.
For example, MRI has been used to monitor the
movement of moisture in wheat grain during
drying (Ghosh et al., 2007) and to visualize non-
homogeneous moisture distribution in the endo-
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