Tanzania Journal of Agricultural Sciences, 2008, 9(1) : 93 - 100
Processing of soybean for human consumption requires wet heat treatment of the beans in
order to inactivate anti-nutritional factors. After hot water treatment or steaming,
dehulling of the bean has always been an uphill task for household processors in Tanzania.
Dehulling is done by hand rubbing, which is tedious and time consuming. The traditional
coffee pulping machine was adapted to dehull boiled soybean. Seven soybean varieties
namely TGX-1876-2E, Bossier, Kaleya, TGX 1805-8E, Sable, Songea and Duicker were
tried. This was a development process whereby three consecutively improved versions of
dehulling machines were tested. The machines were branded Ml, M2 and M3, implying
first, second and third generation, respectively. Bean recovery as a measure of performance
was 74.3, 77.4 and 91.8% for Ml, M2 and M3, respectively compared with 89.7% for
manual dehullingfrubbing. The respective throughput was 8, 10 and 28.2 kg/h compared
with 0.43 kg/h for manual dehulling. The mean dehulling efficiency of the M3 dehuller was
82.4% which was the highest. The M3 dehuller's best performance was due to use of ball
bearings to support the rasping roller axle instead of sleeves and its ergonomically suitable
height. The M3 dehuller could be adopted for soybean dehulling under rural livelihood
conditions but the economics for owning and running it needs to be explored. Its
improvement to make it moiorised is recommended to increase throughput and increase
chances for adoption in medium scale soybean processing.