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Organisation: International Development Research Centre, Canada (IDRC)
Author: O.G. Schmidt
Edited by AGSI/FAO: Danilo Mejia (Technical), Beverly Lewis (Language&Style), Carolin Bothe (HTML transfer)

CHAPTER IX SORGHUM AND MILLET: Post-harvest Operations

2.6 Cleaning

2.8 Storage

2. Post-Production Operations

The applied research supported by IDRC emphasised small scale processing of sorghum and pearl millet near the farm in West Africa, Eastern and Southern Africa, and India. The key hardware technology was the dry abrasive disc dehuller, which was able to remove the seedcoat. Women have traditionally decorticated sorghum and pearl millet to improve the taste and eating quality of the grains. Decorticated grains also benefit the flavour of the flour produced from milling. Manual decorticating was time and labour consuming; the dehuller technology was intended to free women from this drudgery.

The experiences with research on processing of sorghum and millet in the semi-arid areas of Africa between 1970 and 1987 were reviewed in the monograph Abrasive-disk Dehullers in Africa: from research to dissemination (Bassey and Schmidt, 1989). This paper was widely distributed to institutions and libraries in the Third World. The abstract maintained:

"Recent droughts in the Sale and eastern and southern Africa have increased the urgency with which national policymakers are considering drought-resistant crops. National systems for agricultural research in many African countries have strengthened their programs to improve sorghum and pearl millets. A food crop, however, only becomes food when it is actually consumed. Efforts to increase food production must, therefore, be matched by corresponding research on food after harvest. The absence of appropriate dehulling equipment, especially for small grains, has often been cited as a reason for past national neglect of these cereals.

"This publication reviews the development of small-scale, inexpensive, versatile abrasive-disk dehullers in Africa. The rural deployment of mechanical dehullers offers an opportunity to enhance national cereal self-sufficiency and to increase use of the productive capacity of the low-rainfall areas of Africa.

"The topics discussed in detail include the need to understand traditional food habits and preferences; the scope for applying small dehullers in Africa; detailed technical descriptions of various dehuller designs and criteria to be considered in a design process; important grain characteristics as they relate to dehulling and the effect of the dehuller's abrasive agent on the grain; installation and operation of some typical, rural, small-scale milling systems; and the process of introducing technology as one moves from applied research to applying the results."

The scope of the work done in Africa since the mid-80s and in India since 1975 is summarised in the following paragraphs:

West Africa

In Senegal, close collaboration between the National Agricultural Research Institute and a machinery manufacturer led to the latter's marketing of a small-scale dehuller (Mbengue, H.M. 1990, Seck, I. 1990). By now, total volume of sales is in the scores, if not in the hundreds. The agricultural research institute tested village based application of the dehuller technology as small enterprises to the sorghum and the pearl millet subsistence food systems. SISMAR accordingly made the prototype design more rugged, easier and cheaper to build. Technical reports can be obtained from Centre National de Recherches Agronomiques (CNRA), B.P. 53, Bambey, Senegal, and equipment for dehulling and for wet milling can be obtained from Societe Industrielle Sahelienne de Mecaniques de materiels Agricoles (SISMAR), BP3214, Dakar, Senegal.

In Gambia, the Catholic Relief Services modified the original Canadian design of the mini-dehuller, contracted the manufacture of the dehuller to local metalworking workshops, and installed approximately 20 small self-sustaining enterprises serving their own neighbourhoods where pearl millet was the main cereal staple. (For research reports and equipment suppliers contact the Catholic Relief Services, P.O. Box 568, Banjul, The Gambia.)

In Niger, a Canadian-based non-governmental agency, in association with the Ministry of Agriculture and Adult Education Services, tested the rural appropriateness of two dehuller and milling installations as co-operatively owned enterprises in the semi-arid areas which depended on pearl millet as the main cereal staple (Mahamadou, et al. July 1990.). Reports can be obtained from Institut pour L'Etude et L'Application du Developpement Integre. Institute for the Study and Application of Integrated Development (ISAID), B.P 2821, Niamey, Republiqe du Niger.

In Mali, the Compagnie Malienne de Developpement des Textiles (CMDT) (BP 487, Bamako, Mali), sought to improve cotton productivity by introducing dehullers to the participating farmers to alleviate food preparation problems with the sorghum subsistence crop part of each smallholder's lands.

Some early work was also done in Maiduguri, Nigeria in 1972-74, and at the Food Research Institute in Accra, Ghana.

These projects all had an initial introduction of hardware. Closer identification of the household level food problem and testing of the hypothesis that a hardware intervention was the most appropriate kind of applied research, prompted the advent of techniques called Rapid Rural Appraisal to the researchers (Gueye, B. and K. Schoonmaker Freudenberger, 1990; Schoonmaker Freudenberger, K. 1990)

The projects working on dehullers in West, Eastern and Southern Africa participated in a number of workshops aimed towards networking among countries. The purpose was to link the post-harvest research closer to national policy and to biological production-oriented research. Another objective was to document a series of comprehensive national case studies (Bassey, and Schmidt. 1989). Another important issue was to understand the food/feed system from production to consumption in each national or sub-national context. Efforts were focussed certain that applying hardware technology at the rural level was indeed the most cost-effective intervention.

Eastern and Southern Africa

Work in Botswana, proceeded in two stages. Stage 1 between 1976 and 1978, established a small sorghum dehulling and grinding factory with the Botswana Agricultural Marketing Board. In the second stage, between 1978 and 1981, a medium size dehuller was adapted for use by rural milling enterprises, at the Rural Industries Innovation Centre (contact the RIIC, Private Bag 11, Kanye, Botswana for purchasing small milling systems and engineering drawings, as well as for copies of research reports). A minimum of 25 rural enterprises flourished by the early eighties, leading to the formation of the Botswana Mill Owners Association (PO Box 483, Gaborone, Botswana).

It must be emphasised that in the mid-70s sorghum was still the preferred staple grain in the country, partly responsible for the rapid adoption of suitable technology to replace women's manual decortication labour. As one example, within two years of establishing the small dehulling and milling enterprise at the RIIC, it was processing up to 14 tons of sorghum daily in two 8-hour shifts, especially in the first three months post harvest. The majority of the processing was for traders and grocery stores who packaged the flour in 1kg, or 2 kg paper bags, and in 2.5 kg and 5 kg plastic bags with their own brand names. An important part of the mill's activity was to also process the small amounts (5 kg-90 kg) brought by individual families living within walking or donkey cart distance of the mill.

During the 80s, the RIIC manufactured and sold no less than of 70 additional systems for the semi-arid areas of South Africa, formerly known as Bantustans. The manufacture of the dehullers is now being done by two different companies in Botswana, with the RIIC continuing to do the marketing, installation of the machinery and the training of the operators and owners of the enterprises.

In Zimbabwe, the Environment Development Activities-Zimbabwe (ENDA-Zimbabwe, Box 3492, Harare, Zimbabwe) conducted initial rural trials of small-scale dehuller/milling enterprises between 1987 and 1989. Next ENDA became the implementing agency, on the behalf of the Ministry of Agriculture of a CIDA-(Canadian International Development Agency) supported technology-dissemination project (1989-93) resolved to establish up to 60 self-sustaining enterprises. The selected crops were sorghum and pearl millet.

ENDA-Zimbabwe directed an extremely active project on traditional grains. In the project traditional cultivars were exchanged among farmers' groups throughout the semi-arid areas of Zimbabwe, and yield and eating qualities (measures of household acceptance) were being tracked by ENDA. This was done with active collaboration with the National Agricultural Research and Extension systems, and with the SMIP (Regional Sorghum and Millet Improvement Program , PO Box 776, Bulawayo, Zimbabwe) program in Bulawayo. (Note: This project was not funded by IDRC) As the policy criteria began to change, a useful assessment was written in late 1993 by and for ENDA-Zimbabwe on sorghum and millets, also known as the small grains (Rukovo, A. and J. Gwitira. January 1994). In 1992, the University of Zimbabwe's Development Technology Centre (DTC, PO Box MP 167, Mount Pleasant, Harare, Zimbabwe) began a three year project to follow up on enhanced community participation in problem identification and intervention testing to solve problems in the sorghum food systems in the semi-arid areas, particularly in the South of the country. ENDA can supply technical reports, and contact with local equipment manufacturers.

In the early nineties, a regional ENDA was established for southern Africa, and it expanded its program to include dehulling of pearl millet in Namibia. (See also the UK NRI efforts: Hay et al. 1991; Dendy, D.A.V. 1995)

The Ethiopian Nutrition Institute (ENI, PO Box 5654, Addis Ababa, Ethiopia) in the early 80s worked on several threads: measuring the nutritive absorption of sorghum-based gruels in small children, the feasibility of using sorghum flour for the production in volume of injera (unleavened fermented pizza-sized flat "breads") by a state food supplier, and the incorporation of sorghum flour in weaning foods manufactured and marketed by a state corporation. Prevailing policy inhibited the impact of the work.

Parallel to this attempt the Institute of Development Research (IDR, Addis Ababa University, PO Box 1176, Addis Ababa, Ethiopia), placed one dehulling-milling system with a rural agricultural co-operative, in conjunction with the Alemaya University in the province of Hararghe. State policies, still in effect, sought to replace all individual enterprise ownership with co-operatives (with little entrepreneurial skill), The experiment was affected first by Ethiopia's severest drought in the mid eighties, and, later, by a change in government which established a new policy framework.

The Kenya Industrial Research and Development Organisation (KIRDI, PO Box 30650, Nairobi, Kenya) in the mid-80's accrued useful knowledge about the technical and economic feasibility of processing sorghum and pearl millet by mechanical means. However, the involvement of small-scale entrepreneurs, and the accrual of knowledge about enterprise development did elude that IDRC-supported project. KIRDI did achieve a useful survey on the acceptability of dehulled (pearled) whole sorghum grain by the general population and institutions such as schools (Anonymous. 1990). KIRDI can supply research reports, as well as contacts with local equipment suppliers.

The University of Nairobi's College of Agricultural and Veterinary Science, (c/o Dean of Agriculture, P.O. Box 29053, Kabete, Kenya) also conducted a related project, Sorghum and Millet Food/Feed System, which sought to encourage increased networking among all national researchers who were active on aspects of the crops from production to consumption. They convened several national workshops, did some field-work and maintained a modest, specialised library collection on the topic. (See also Singh et al., 1992)

In Tanzania, the Small Industries Development Organisation (SIDO, PO Box 2476, Dar es Salaam, Tanzania) starting from 1979 conducted two phases of IDRC-supported efforts to determine where and how small enterprises dehulling and milling of sorghum would fit into the rural situation. Prevailing agricultural policy, weak rural infrastructure, long distances from Dar es Salaam to the experimental sites in the drier west, and punishing road conditions militated against useful results. Research reports and contact with local manufacturers can be obtained by contacting SIDO.

A companion project on sorghum utilisation at the Sokoine University Department of Food Science in Morogoro (PO Box 3006, Morogoro, Tanzania) provided some useful technical insights, but had little impact on utilisation of sorghum by the populace.

The Sokoine University's Department of Agricultural Economics, in collaboration with the Regional Sorghum and Millet Improvement Program (SMIP) in the early 90s studied the trading and pricing system of sorghum and millet in the post-liberalisation economy providing important knowledge for policy formulation. A national workshop was held in May 1993 in Arusha and workshop proceedings can be obtained from the sponsors.

The Zambian Small Industries Development Organisation (SIDO, PO Box 35373, Lusaka, Zambia) began in 1986 to experiment with dehullers in rural settings. Weak infrastructure and foreign exchange limitations, as well as staff limitations resulted in indifferent findings. Similarly, few useful results seem to have been achieved by the work done by the Uganda National Council for Scientific and Industrial Research, at a time when that country was under extreme military and economic stresses.

In 1987 the Sorghum and Millet Improvement Project (SMIP) of the Southern Africa Development Cupertino Conference (SADCC), implemented by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), held a conference to review the utilisation of sorghum and millets, and IDRC presented its experiences there (Schmidt, O.G. 1992). There has been a continuing interaction between these two institutions on the subject of the semi-arid food grains.

The Post Production Systems Group of IDRC paid increasing attention to two issues, which related to the foregoing group of projects, which had a technology-led theme. The two issues were to improve national knowledge of the total food system of sorghum and pearl millet, and to link this understanding more directly to national grains marketing policy issues. As well, IDRC sought to bring about a closer dialogue among the national food systems researchers and international donors in the post harvest area (Anonymous. 1987, Anonymous. 1991; see also Rohrbach, 1990).

Sorghum and pearl millets have significant impact on the nutrition of the human body, especially for young children, in areas where they are the main staple cereals. A workshop in 1987 examined current knowledge about household level food preparation techniques, including those for sorghums and pearl millets (Alnwick, D., S. Moses, and O.G. Schmidt, eds. 1987). These proceedings of the workshop can be worthwhile to the village level nutrition worker and to the food scientist.


Between 1975 and 1990, researchers at the College of Home Science of the Andhra Pradesh Agricultural University (APAU) in Hyderabad were involved in a systematic process of promoting the utilisation of sorghum (Pushpamma, P. 1993). The abstract of the book will gives a good description of the topics addressed:

"The need to increase the use of sorghum is explained and the current food system using sorghum is described, looking at improved varieties, marketing, storage, current processing and utilisation methods, and the nutritional status of sorghum foods. The effects of dehulling on product quality and nutrient status are considered, emphasising that flour from sorghum milled in the right way can compete with wheat and rice flours, at much lower cost, in areas where sorghum is extensively grown. Finally, the problems of using sorghum as a substitute in popular and traditional cereal foods are considered and the details of successful food enterprises based on sorghum, with active support from Andhra Pradesh Agricultural University, are described. Various countries have attempted to get this kind of work done: nowhere else has the whole chain of research been so logically and successfully designed and carried through right to the point of successfully promoting small-scale, sorghum-based, food enterprises."

Here is a brief description of the applied research process:

"During the first phase of the project, market surveys were carried out in three agroclimatically different regions of the state-Coastal, Rayalaseema, and Telangana-to assess production, storage, processing, and consumption practices for sorghum and their effects on nutritive availability."

"The second project phase was to elaborate feasible ways of upgrading these operations using a small mechanical dehuller to remove the drudgery of traditional processing methods and obtain sorghum products that could be used in a wide range of popular foods, including weaning and supplementary foods for infants and mothers. Extensive field testing was conducted to establish the levels of demand for mechanical dehulling systems in rural Andhra Pradesh and the acceptability of products based on dehulled sorghum."

"The last project phase concerns attempts to develop feasible systems for establishing small enterprises based on sorghum processing to produce nutritive foods for rural-household, semiurban, and urban markets in Andhra Pradesh. Also, the feasibility of developing small enterprises operated by women was considered as a means of directing additional income specifically to vulnerable socio-economic groups-women, children, and infants-and have a positive impact on improving nutrition in the poorer sectors. (Two extensive existing government programs-Integrated Child Development Services (ICDS) and Development of Women and Children in Rural Areas (DWCRA)-were identified to serve as channels for implementing such activities regionally)."

The previous document was written for scientists. Dr. Pushpamma had the opportunity to present the experiences summarized above in the form of a manual, as a case study of Development Market Research and Social Marketing (Pushpamma, P. 1994). This version is written for the lay practitioner who is involved in social development activities.

A related study, centred on the western dryland region of India, highlights the utility of rapid rural appraisal (RRA) in assessing community nutrition problems and formulating recommendations for nutritional improvement (Kashyap, P. and R.H. Young. 1989). The village of Parbhani is located in Maharashtra State, India.

Special mention should be made of John Cecil's work on industrial milling of sorghum, work which anticipated questions about the technical and economic feasibility (Cecil, J.E., 1986). The work will probably be highlighted by the submission from the UK Natural Resources Institute (NRI).

2.6 Cleaning

The main distinction is between industrially processed bulk grain and small lots (5-90 kg) brought to a small-scale dehulling/milling enterprise by individuals. In the former case, stone removal and soil sifting equipment are required. In the latter, the household has already cleaned the crop with great care since the grain is to be used for the family's food eliminating the need for additional cleaning.

2.8 Storage

In the African context, it is important to distinguish between a subsistence crop which provides food for the household, and a cash crop sold to industrial processors. The smallholder subsistence farmer, from Ethiopia to Southern Africa uses "traditional" seeds. These are non-hybrid low yielding species with the preferred food and taste qualities. Often a mix of cultivars are planted to spread the risks against drought and pests while in the field. The cortex is extremely hard and insect resistant. Storage of traditional varieties does not present a major problem. For example, there are traditional hard varieties in Zimbabwe, which store well for years, maintaining good seed viability. Problems of storage have emerged as farmers adopt higher yielding varieties, with softer cortexes or other propensities to insect and mould infestation.

The industrial processing of sorghum for food was systematically inhibited by state policies in Africa until the mid to late 80s. It is advised that readers refer to ICRISAT contribution for relevant technical information on storage for industrial processing, or contact commercial manufacturers of processing machinery.


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