DEVELOPMENT AND PERFORMANCE EVALUATION OF DRYING, MILLING AND SIEVING MACHINES FOR A POUNDO YAM FLOUR PROCESS PLANT

Abstract

Yam, Dioscorea (Spp.), is an important source of carbohydrate for many people of sub-Sahara region, especially in the West Africa. It is mostly taken as pounded yam. The process of making pounded yam is highly energy consuming, therefore, the instant pounded yam flour, commonly called poundo yam flour, has become popular in West Africa. Since manual method of producing this flour is slow and unhygienic, there is need for the process plant that will produce this poundo yam flour from raw yam tubers. This work, being the second phase of the process plant presents the development of quick and effective conveyor system, drying, milling and sieving machines which are made to permit direct flow of parboiled chipped yam from one machine to the other without manual materials handling. The dryer with capacity of 0.0255 m3 was designed such that it dries the yam at a temperature of 500C. The yam cubes from dryer are then passed into the milling machine and finally a sieving machine makes the poundo yam flour into fine powder. The efficiency of the dryer was 71.7% with drying rate of 5.75 kg/hr, producing yam chips with moisture content of 9%, the milling machine had efficiency of 97.5% with milling capacity of 0.063 kg/s while the sieving machine gave an efficiency of 96% with sieving capacity of 0.0767 kgm2/s. The processes took four hours. A sensory evaluation carried out on the product shows high level of acceptability. The materials used for the fabrication of the machines were sourced locally and the cost of fabricating the machines was one hundred and twenty two thousand eight and fifty naira only. The maintenance procedure for the machines is highlighted