Investigation of selected independent variables on extrusion of rice semolina with and without propeller

¹ Department of Machines and Apparatuses for Food Industry Technical Faculty, University of Food Technology, 4002 Plovdiv, Bulgaria
² Department of Canning and Refrigeration Technology, Technological Faculty, University of Food Technology, 4002 Plovdiv, Bulgaria

^* Corresponding author: asimitchiev@uft-plovdiv.bg

Abstract

The influence of screws with and without propeller, as well as the independent variables of material moisture content, working screw speed, feeding screw speed and die temperature on the changes of some physical and mechanical properties during singles-screw extrusion of rice semolina was studied. The response surface methodology was used with an orthogonal central composite design. Optimum modes of operation which lead to the maximization of the mass flow rate and the sectional expansion index and the minimization of the specific mechanical energy were established. The obtained results show that the use of a propeller in single-screw extrusion leads to an increase in extruder mass flow rate, a decrease in the specific mechanical energy and an increase in the sectional expansion index.