Journal of Natural Sciences Research www.iiste.org ISSN 2224-3186 (Paper) ISSN 2225-0921 (Online) Vol.5, No.12, 2015 12 Energy Consumption and Efficiency in Single Screw Extrusion Processing of Selected Starchy Crops Folasayo Fayose 1* Zhongjie Huan 2 1.Agricultural and Bio-Resources Engineering, Federal University Oye-Ekiti. Nigeria 2.Tshwane University of Technology, Pretoria, South Africa * E-mail of the corresponding author: folasayo.fayose@fuoye.edu.ng Abstract The substantial amount of energy consumed during food processing and energy consumption is a very significant factor of operational costs. Also, consumption of products of starchy crops like cassava, maize and wheat is the common feature of low income dwellers of Africa. Improvement of these diets by fortifications with essential components of food including proteins, vitamins and minerals is desirable. Extrusion cooking has been proven to be a very efficient food processing technology that is capable of performing several unit operations simultaneously. Knowing extruder efficiency enables one to evaluate the overall machine performance and potential which has an important industrial value. In this study, the torque, pressure and energy requirements for processing the flour and starch of maize and cassava and wheat flour at by a locally developed extruder were estimated and the energy efficiency determined. The study showed that the efficiency of the extruder depends on the material that is being processed. Also, die pressure increased with increase in specific mechanical energy (SME). Except for cassava flour, there was improved torque at moisture contents ≥ 30% d.b. Moreover at the selected settings on the extruder, its efficiency was high for cereal products whereas it was very low for cassava products. Further study is recommended on how to attain high efficiency for the processing of cassava products. Keywords: Extrusion, Efficiency, Specific Mechanical Energy, Torque, Starchy crops 1. Introduction Extrusion technology is very important to the food industry because it has been proven to be energy efficient manufacturing process (Aruna 2012). However, records of local development of food extruders in developing countries have been sparse. This is despite the fact that the diets of dwellers in these regions are predominantly starchy crops, which have great extrusion potentials. Improvement of these starchy diets by fortifications with other essential components of food including proteins, vitamins and minerals by extrusion is desirable. Extrusion cooking has been proven to be a very efficient food processing technology that is capable of performing several unit operations simultaneously. A wide range of products, which cannot be produced easily by any other process, is possible by changing the ingredients, extruder operating conditions and dies while working at lower processing costs and higher productivity with no process effluents. Food extrusion is an energy efficient process because a substantial amount of the mechanical energy from the drive motor is dissipated during the viscous flow within the channels of the extruder screw (Harper 1985). Sufficient availability of the right energy and its effective and efficient use are prerequisites for improved agricultural production particularly for small holder farming. Also, in the world at large, energy issues are now receiving considerable attention as its cost of production is increasing by the day. Energy efficiency has been a major concern for Engineers because it is a very significant factor of operational costs. According to Liang et al. (2002), energy consumption and extruder efficiency for food extrusion are complex functions of the properties of processed material, design of extruders, type of motor drive and extrusion conditions. Due to the complex relationships of the food, the water, and the extrusion conditions, a number of efficiency measures can be worked out, each appropriate to circumstances and therefore selectable to bring out special features important in the particular process. Energy efficiencies are also meant for providing an objective comparison between different extruders and extrusion processes. Knowing extruder efficiency enables one to evaluate the overall machine performance and potential which has an important industrial value. It is necessary to determine the energy efficiencies in preliminary studies of extruders so as to understand and know the extruder’s profile under any condition and to be able to control it effectively for any particular application. This study, therefore, was undertaken to evaluate the performance of a locally developed extruder with a view to improve on it. 2. Materials and Methods The study was conducted as follows: 2.1 Estimation of Parameters According to Liang et al. (2002), extruder efficiency is considered the theoretical power required divided by the actual power consumed. The extruder efficiency, η, is defined as: