Energy Consumption and Efficiency in Single Screw Extrusion Processing of Selected Starchy Crops

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