Energy considerations on extrusion of Tarhana, a wheat flour based product

Abstract

Tarhana, a traditional Turkish cereal food, was extruded using a twin-screw extruder. The effect of the changes in barrel temperature (60–120C), feed rate (10–20 kg/h, wet basis) and screw speed (100–300 rpm) on the mechanical and thermal energy inputs was investigated. Energy balances showed that increasing barrel temperature tends to reduce the contribution of heat energy converted from the mechanical energy (ME) to the total heat energy absorbed by tarhana. The use of high-screw speeds at relatively high barrel temperatures and at low feed rates is not suitable from an energy point of view because only a small portion of the ME introduced into the system is absorbed by tarhana. It is concluded that higher barrel temperatures, lower screw speeds and higher feed rates are more suitable for economic tarhana extrusion.