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Processing pulses

The compact small-scale processor developed in Sri Lanka

Processing has been identified as a major constraint for introducing pigeonpea into new areas as the dehulling and splitting process is relatively more difficult than for other pulses. In India, the majority of pigeonpea production is processed as decorticated splits, commonly known as dhal, by more than 10,000 commercial medium to large-scale dehulling mills. In Eastern Africa, similar mills have been installed to meet local and export needs. However, there has been no small-scale dehulling machine available that is capable of producing dhal of the high standard required. The problem with pigeonpea processing lies in the glue that sticks the cotyledons to the seed coat and this has to be dissolved to produce high-quality dhal.

In Sri Lanka, pulses such as cowpea (Vigna unguiculata), green gram (Vigna radiata) and black gram (Vigna mungo) are cultivated under subsistence farming systems in the dry and intermediate rainfall zones. In rural areas, manually operated stone mills (essentially designed to grind grain into flour) have been used for centuries to process dhal from these pulse crops. Lentil, which is not grown locally and has to be imported, is also a popular pulse used in dhal in Sri Lanka. Pigeonpea, which has been identified as a good substitute for lentils, is able to thrive under the marginal growing conditions of the island. However, the stone mills are unsuitable for processing pigeonpea dhal and it has been necessary to develop an appropriate small-scale mill suitable for farm-level processing of pigeonpea.

With support from the Asian Development Bank, ICRISAT scientists have been able to work with Sri Lankan counterparts to design and manufacture a small, portable, medium-volume (40kg per hour) dehulling mill. After extensive testing in the field, the technology has now been transferred to a private company in Sri Lanka. The unit can be operated at low cost and, because it also is able to process other pulses, it has already been well received in Sri Lanka and ICRISAT is transferring the technology to partners in Southern and Eastern Africa. The African Development Bank for the Improvement of Pigeonpea in Eastern and Southern Africa is also sponsoring trans-continental sharing of the traditional Indian household pulse dehulling grinding stone, known as the chakki.

Increased availability of small-scale and household processors will provide more farmers with the opportunity to grow pigeonpea. In addition, by eliminating the middlemen, farmers are able to produce a high-quality added value product.

Information source: A new small-scale processor for pulses by H M Nimal Jayantha & K B Saxena, ICRISAT Information Bulletin No. 54, 1998.

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