RA 00048.pdf - OAR@ICRISAT

Sorghum Nutritional Quality-
Progress and Prospects
J. D. Axtell, Gebisa Ejeta, and L. Munck*
The aim of this symposium is to assess the
current status of research on sorghum and to
discuss prospects and opportunities for further
research during the decade of the 1980s. Hulse,
Laing, and Pearson (1980) have recently published
an extraordinarily comprehensive and thorough
review entitled "Sorghum and the Millets: Their
Composition and Nutritive Value." Their introduction
includes the following statement which we
believe sets the stage for the presentation of this
paper at this symposium. Hulse et al. (1980) state
that "Sorghum and the principal millets, apart
from their use in animal feeds, are the staple
foods of many of the world's poorest people:
people whose nutrient supply is invariably at risk.
The nutritional quality of the grains should therefore
be a matter of primary consideration for all
those working towards their genetic and agronomic
improvement."
We will review briefly the status of current
research on nutritional quality of sorghum and
then focus on prospects and opportunities for
future research.
Basically sorghum contains just as high levels of
the major nutrients—starch (68-73%) and protein
(9-14%)—as the cereals which are considered
the most nutritious. However, three major
factors complicate the full utilization of this rich
store of starch and protein.
First, protein and energy availability is limited in
some sorghum genotypes by the presence of
* Professor of Genetics, Dept. of Agronomy, Purdue
University, West Lafayette, Indiana 47907, USA;
ICRISAT Sorghum Breeder, ICRISAT Sudan Cooperative
Program, P.O. Box 126, Wad Medani, Sudan; and
Head, Dept. of Biotechnology, Carlsberg Research
Laboratory, Gamle Carlsberg Vej 10, DK-2500 Valby,
Copenhagen, Denmark, respectively.
polyphenolic compounds (tannins) located primarily
in the testa layer of the grain. These pigmented
compounds are just recently being chemically
characterized (Butler 1982) and are traditionally
being referred to as "tannins."
Second, the protein quality of an all-sorghum
diet is limited by the low lysine content of the
grain which reflects the high prolamine content of
the endosperm. If one looks at the essential
amino acid composition of sorghum grain, in
comparison with monogastric nutritional requirements,
it is obvious that lysine is deficient and that
there is a great excess of leucine in comparison
with isoleucine, while there are no major deficiencies
in the other essential amino acids. We will
discuss two ways of solving the protein quality
problem in sorghum, i.e., breeding for high lysine
sorghum and dietary supplementation with proteins,
for example from legumes.
Third, there are specific dietary limitations in the
utilization of cooked and baked sorghum products
for humans due to factors such as the high
gelatinization temperature of the starch and the
high viscosity of the cooked products leading to
significant problems with regard to acceptability
and digestion. To cope with these problems, local
food preparation techniques have been developed
often relying on specific local varieties. In the
International Symposium on Sorghum Grain Quality
(ICRISAT 1982) this interaction between food
habits and sorghum varieties was described, for
the first time, in a comprehensive way. Finally, we
will also find that processing of sorghum could
also be beneficial in animal nutrition.
T a n n i n s
Butler (1982) has presented an excellent review of
the biochemistry of sorghum tannins and polyphe-
International Crops Research Institute for the Semi-Arid Tropics. 1982. Sorghum in the Eighties: Proceedings
Symposium on Sorghum, 2-7 Nov 81, Patancheru. A.P., India. Patancheru, A.P. India: ICRISAT.
of the International
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