DEVELOPMENT OF A PROCESS PLANT FOR THE PRODUCTION OF VEGETABLE LEAF POWDER

Abstract

Achieving food security is a huge task that is desirable and one of the key agenda of sustainable development goals (SDG). Thus, there is an urgent need to match all efforts made towards increasing crop production with commensurable post-harvest technologies needed to drive preservation of agricultural produce from spoilage and wastages being experienced. This research therefore focuses on the development of a process plant for the production of vegetable leaf powder. The vegetable leaf powder process plant consists of five sections namely; vegetable leaf washing, pre-drying, drying, milling and packaging sections. Detailed design analysis of all the machines involved in the production process was done and Computer Aided Design (CAD) model for the process plant was done using Solidworks software. In order to ascertain the functionality, stability, integrity and manufacturability of these machines when fabricated, section by section simulation of the design was carried out using Solidworks software. In fabricating the machines that make up the process plant, locally sourced materials were used. The fabrication of the drying, milling and packaging sections had been completed using appropriate fabrication techniques. For the automation of the plant, modular approach was used to implement the control system on each machine. On the simulation of some of the machine parts, solidworks von mises analysis was carried out on the water bath of the vegetable leaf washing machine with Stainless steel AISI 304 selected and the results showed that with total designed load of 9.5 kN, a maximum allowable stress of 5.145×108 N/m2 was obtained which is below the yield strength of 6.20422×108 N/m2 of the selected material. The maximum elongation obtained under the loading condition was 14.2902 mm, which is minimal for any failure to occur or reduce life cycle of the base material. Simulation results for other machine parts such as shaft, roller paddle, perforated screen, temporary storage device, dryer and machine frame that were carried out indicated that these machine parts would satisfactorily perform their intended purposes. Before evaluating the performance of the vegetable leaf dryer, dryer pre-heat time under varying voltages was determined to establish time taken to build temperature of the dryer before loading vegetables. While it took 36 minutes to pre-heat the drying chamber to 60 oC under voltage range of 220- 225 volts, it took 40 minutes to pre-heat the dryer to 60 oC under a constant voltage of 220 volts. Recorded pre-heat time was 52 minutes when the voltage fluctuated between 200-210 volts. For the performance evaluation of the process plant, three vegetable leaf samples were used to produce vegetable leaf powder namely; bitter leaves, scent leaves and moringa leaves. 200 grammes of the selected leaves at drying times of 50, 60 and 70 minutes were dried and the results from dryer showed a steady increase in rate of moisture removal as the temperature increased due to increase in air-heat supply rate to the leaves and the acceleration of moisture migration within the chamber. The evaluation of milling and packaging machines was also carried out and 300 grams each of dried vegetable leaf samples were milled. The milling machine crushing efficiencies were 90.7%, 90.53% and 89.73% for bitter leaves, scent leaves and moringa leaves respectively. The performance evaluation of the packaging machine showed that the machine has the capacity to package 6 packaging bottles of 100 grams of vegetable leaves powder per minute and 320 packaging bottles per hour, thereby reducing the stress experienced while using traditional method of vegetable powder production. Proximate analysis of bitter leaf and scent leaf powder produced showed that at the drying temperatures of 50oC, 55oC, 60 oC and a constant drying time of 50 minutes, both vegetable samples retained their nutritional contents, given aggregate of: 32.375% of protein; 3.474% fat; 6.238% fibre and 45.653% carbohydrate. Therefore, it can be inferred that some active ingredients of vegetable leaves can still be preserved using this processing plant, thereby extending the shelf life of leafy vegetables and making it available throughout the year.