Extrusion is a mechanical process in which certain materials are forced, under pressure, through a die opening to create products of a desired shape, size, and/or texture. In the case of food production, if the food is heated by external heaters during the process, it is referred to as extrusion cooking, a relatively new and advanced food processing technique. Due to its processing flexibility, extrusion cooking produces an incredibly broad range of food products, most notably in the cereal, dairy, bakery, and confection industries. Legume flours are often used as the basis for formulations that are extruded in low pressure systems. The flour is mixed with water and other starch-based ingredients to achieve a level of dough consistency that is suitable for extruding and will produce a texture and taste that is acceptable to consumers.
It is possible to produce puffed snacks from 100% pulse flour. Parameters to be considered when processing pulse based extruded snacks are listed as follows:
- Starch, dietary fiber and protein content of raw materials
- Amylose/amylopectin ratio of starch/starch blend
- Type of extruders (Single or Twin screw)
- Shapes of the snack
Chemical composition of raw materials is the single most important variable in the extrusion. Starch is what makes the product puff, and the starch composition ratio of amylose and amylopectin affect the rate of expansion as well as texture of the final products. For instance, presence of non-starch materials in the flour blend reduces the expansion. Similarly, high amylose contents tend to make products denser while high amylopectin contents provide crispier texture.