RA 00048.pdf - OAR@ICRISAT

Figure 10. Photograph of the TADD used to predict dehulling quality. (Oomah et al. 1981.)
the abrasive ring (c) positioned on the periphery of
the chamber. Fines are blown through a perforated
metal screen (d) and into the collector (e).
After removing the screen, dehulled grain is
blown into a second collector. Impeller blade
speed, which can be controlled (f), number of
blades, and surface grit size of the abrasive ring
affect the decortication (Shepherd 1981a).
Shepherd (1981b) has used staining techniques to
determine the degree of decortication.
Conclusions
The need for mechanical processing systems to
replace traditional hand pounding methods has led
to much activity in this area in the last 10 years.
Much of the research has concentrated on the
development of suitable dehulling equipment for
sorghum, since other aspects of milling this grain
(cleaning, grinding, etc.) have been much less
problematic. Most of the work described in this
chapter is only in the development or early
application stage. Therefore, on the basis of only
very limited data on dehullers and some complete
milling systems, it is very difficult to make many
solid recommendations. Detailed publications describing
new mills and the application of new
dehulling equipment to sorghum grain are required.
Such reports should include throughput,
power consumption, maintenance requirements,
a detailed description of the machinery, cost, and
data on the efficiency of dehulling in terms of fat,
ash, and color reduction and other nutrient losses.
Parameters affecting the throughput or efficiency
of dehulling should be studied and results at a
number of extraction levels should be reported.
Ideally, comparative studies of dehullers yield
the most valuable information. It is essential that
the same variety and lot of sorghum be used in
such studies since the performance of dehullers is
markedly dependent on the characteristics of the
grain. For example, throughputs can vary by a
factor of 2 or 3 between a soft and a hard
sorghum variety. Comparative studies need to be
conducted to optimize the abrasive surface in
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