RA 00048.pdf - OAR@ICRISAT

which is a reasonable figure with the current food
situation in Tanzania, the products will be much
darker than products made from the local hard
varieties, and thereby paving the way for competitive
maize products.
Hand pounding is hard and tedious work. It
takes up to 1 hr to process 2 kg of sorghum. Thus
there is a ready market for small diesel-driven
village mills serving individual farmers who bring
their own batches to the mill. However, in our
experiment (Table 1) we showed that such a
technique is just as dependent on endosperm
hardness as the hand pounding technique. Milling
of Lulu D in a Tanzanian village mill gave a darker
flour (Plate 1 : c) than a hand decorticated flour
from the comparable variety 2Kx17/B/1 and just
as intolerably high losses of starch and protein as
the latter (Table 1).
Nutritional Quality
of Sorghum Products
The content of digestible nutrients in low-tannin
sorghum products is very high compared with
other cereals (Table 2, Eggum et al. 1982). The
true digestibility of protein and energy in decorticated
grain is 100% and 9 6 % respectively. When
sorghum is cooked to make "ugali" porridge,
these values decrease by 8% and 2% respectively.
Although the digestibility of sorghum decreased
through cooking, the values before and
after cooking, are comparable with the best
values for other cereals such as wheat, maize, and
rice. However, the lysine value is very low (Table
2) and decreases by 4 0 % during decortication.
Because lysine is the nutritionally limiting amino
acid in sorghum, the biological value of sorghum
protein is the lowest of all cereals. By supplementing
with lysine-rich foods such as beans
and vegetables, the high potential of digestible
protein and energy in sorghum can be fully
utilized.
Developing a N e w Milling
Technology for Sorghum
The need for a new sorghum milling technology
has been recognized earlier by the Canadian
International Development Research Centre
(IDRC) and FAO. IDRC (Eastman 1980) has
developed a small batch mill for local machine
milling of sorghum using carborundum or silicium
stones. Likewise, FAO has initiated a program for
sorghum milling (Perten et al. 1978) on an
industrial scale. This system also relies on an
abrasive principle.
Mechanisms of hand pounding are very different
from those of abrasive milling. In hand
pounding the pestle causes a mechanical shock
which generates strong interactive forces in
between grains as well as between grains and
equipment. When water is added, large flakes of
hull material are formed. On the other hand, in
abrasive milling the polishing effect is mainly
obtained between the grinding stones and the
seeds and as action of seeds against seeds,
thereby producing fine bran particles. Abrasive
milling through kernel breakage causes losses of
endosperm in the bran fraction. However, hand
pounding initially produces coarse endosperm
particles that dwindle during the successive cycles
of decortication. At the Carlsberg Research
Laboratory we have developed an industrial decortication
process aimed at avoiding the disadvantages
of abrasive milling and incorporating the
advantages of the age-old hand pounding principle
(Munck et al. 1982).
In the new decortication machine (Fig. 2) (UMS
DVA, United Milling Systems A/S, DK-2500
Copenhagen-Valby, Denmark) the sorghum ker-
Table 2.
Nutritional quality in rat tests of the improved variety 2Kx17/B/1 (comparable with Lulu D) and the
hand decorticated grain at well as the cooked product ugali (Eggum et al. 1982).
True digestibility
protein
Digestible
energy
Biological
value of protein
Lysine
g/16gN
Whole grain
Hand decorticated grain
Ugali
95
100
92
90 56
96 47
94 49
2.0
1.2
1.2
567