Performance Testing of Small-Scale Equipment for Depulping Locust Bean Seed

Abstract

<abstract> <b><sc>Abstract.</sc></b> Processing of African locust bean seed starts with pretreatment of the harvested fruit before the seed can be converted into its numerous derivatives. Depulping of locust bean seed precedes cooking in locust bean processing. This operation requires much time and energy, which poses difficulties for the women and children who are involved in the processing of locust bean. This study focused on the development of small-scale equipment for depulping of African locust bean seed. Design, construction, and testing of the equipment were undertaken. The techno-economic status of the women in the rural areas who are directly involved in the processing of locust bean and its derivatives was taken into consideration. The depulping machine comprises a vertical cylindrical container, a cylindrical sieve, and a vertical rotating shaft that carries paddles and brushes. The vertical shaft is mounted at the central axis of the depulping unit. The machine has a capacity to depulp 10 kg of locust bean seed in a batch operation. Performance evaluation of the machine was carried out at five levels of soaking time (15, 30, 45, 60, and 75 min), corresponding to five levels of locust bean moisture content (20%, 25%, 30%, 35%, and 40% w.b.), and five operating speeds (550, 450, 350, 250, and 150 rpm). Results indicated that the depulping efficiency varied between 64% and 98% at moisture contents of 20% to 40% w.b. Seed membrane detachment and seed damage were less than 5% and 9.2%, respectively, at 45 min soaking time (moisture content of 30% w.b. with water at room temperature) and 350 rpm operating speed. The maximum power requirement was 2.25 kW at 550Â rpm. The operating conditions of 350 rpm operating speed and 45 min soaking time indicated higher depulping efficiency (98%), lower seed membrane detachment (2%), and lower seed loss (4.5%) during depulping. The performance results showed that the mechanized depulping process compared favorably with the traditional method in terms of quantity of seed produced per batch operation.