CONVENIENCE AND HEALTH FOODS 3 (1+2)

Lesson 8 : Extruded Foods

Types of Extruders

A wide variety of extruders are available with different designs and configurations. Single screw, twin screw (co rotating and counter rotating screws), extruder, conical counter rotating twin, screw extruder, extruder with short screws and long screws, forming extruders etc. they are classified based on their applications (Table.1)

The parts of extruder

1. A holding bin for mixed raw materials.
2. A feeding device to feed the raw, dry mixed, ingredients uniformly in uninterrupted manner at desired flow rate.
3. An extruder assembly made up of barrel segments, screws which knead, cook and dry the food material cook and dry the food material.
4. A die to restrict the extruder discharge and shape the final products.

Table 1. Extrusion Equipment

Sl No	Type	Product Characteristics
1.	Pasta extruders	For pasta products
2.	High pressure forming extruders	For un-puffed pellets
3.	Low shear cooking extruders	for soft moist pet foods
4.	Collect extruders	For dry feed materials such as corn grits.
5.	High shear cooking extruders	For snack foods
6.	Autogenous extruders	No heat is added or removed
7.	Isothermal extruders	Constant temperature is maintained throughout the barrel.
8.	Polytrophic extruders	Heat is alternately added or removed.