June 08, 2016

08/06/2016: Extrusion: an overview

by Dr Mian Riaz, Director, Food Protein R& D Centre, Head - Extrusion Technology Program, Graduate Faculty, Nutrition and Food Science Dept, Texas A&M University

First published in Milling and Grain, April 2016

Extrusion is simply an act of forcing material through a die. High cooking temperature, pressure, and moisture transforms the raw material into cooked and formed products.

There are several functions/actions that take places during the short time. Several types of extruders are used for the manufacturing feed and pet foods. Some are single screw, some are twin screw, some have internal steam locks, some have grooved barrels, some have continuous flighting, and others have interrupted flighting. Some extruders generate their own heat by friction for cooking and other use additional heat sources like stream for cooking purpose. All these extruders work depends upon the application.

Due to the abrasive nature of feed and pet food, proper selection of the materials of construction is important to minimize operating costs. If screw and barrels wear too frequently, the costs of operating an extruder may become prohibitive and ultimately lead to shut down of the extruders.

Extruders are not new. Very short L/D (barrel length/diameter) high shear extruders for making puffed snack foods have been manufactured for over 70 years, single screw cooking extruders for nearly 35 years and co-rotating twin screw extruders for 40 years. Presently, extruder manufacturers are trying to make these extruders more efficient and less expensive. There are approximately 25 major extruder manufactures domestically and overseas.

Read the full article in Milling and Grain HERE

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