EFFECT OF MOISTURE CONTENT ON THE ENGINEERING PROPERTIES OF AFRICAN YAM BEAN (RED COATED)

ABSTRACT The engineering properties of red- coated African Yam Bean (Sphenostylis stenocarpa) were investigated to provide critical data for its processing and utilization. Physical properties such as major diameter, intermediate diameter, minor diameter, and geometric mean diameter of the seeds were measured, with values ranging from 7.08 mm to 8.336 mm, 6.043 mm to 6.870 mm, and 5.966 mm to 6.878 mm, respectively. The sphericity was found to increase with moisture content, ranging from 6.54% to 7.33%, indicating that the bean shape approaches a spherical form as moisture content rises. Surface area also increased from 10,902 mm² to 87,198 mm² as moisture levels increased from 13.20% to 23.20%. The static coefficient of friction was evaluated on glass, stainless steel, and galvanized steel surfaces, with values ranging from 9.10° to 10.08°, 13.40° to 15.10°, and 15.30° to 17.10°, respectively. Additionally, bulk density rose from 0.615 kg/m³ to 0.796 kg/m³, while true density increased from 87.50 kg/m³ to 278.00 kg/m³, corresponding with rising moisture levels. Mechanical tests showed a decrease in compressive strength from 1.38 MPa to 0.09 MPa as moisture content increased, indicating a loss in structural integrity. Thermal properties, such as thermal conductivity, ranged from 1.717 W/m°C to 2.828 W/m°C, while specific heat capacity increased from 0.204 J/g°C to 0.415 J/g°C with rising moisture content. These findings are crucial for optimizing the design of processing and handling equipment for African Yam Beans. The results contribute valuable insights into the behavior of this legume under varying moisture conditions, facilitating its efficient use in food and industrial applications. African Yam Bean (*Sphenostylis stenocarpa*), an underutilized legume, presents significant potential for addressing food security challenges due to its rich nutritional profile and resilience to adverse environmental conditions. However, there is limited research on its engineering properties, which are crucial for optimizing processing methods and designing suitable equipment. This study investigates the physical, thermal, and mechanical properties of African Yam Beans, particularly the effect of moisture content on these characteristics. The experiments revealed that increasing moisture content (from 13.20% to 23.20%) resulted in significant changes in the bean’s physical dimensions, including a rise in geometric mean diameter from 48.095 mm to 58.077 mm. Bulk density and porosity also increased, indicating swelling and structural changes. Mechanical tests showed that compressive strength decreased as moisture content rose, from 1.38 MPa at 13.20% moisture to 0.09 MPa at 21.60%, reflecting the weakening of seed structure at higher moisture levels. Thermal conductivity increased from 1.717 to 2.828 W/m°C as moisture content rose, enhancing the seed's capacity for heat transfer. These findings highlight the importance of moisture content in influencing the physical, mechanical, and thermal properties of African Yam Beans. The data generated are essential for the development of processing and handling equipment, facilitating the efficient use of this crop in industrial applications. This research contributes valuable insights into the potential of African Yam Beans as a sustainable food source, offering practical applications for food security and agricultural engineering.