Raw material behaviors in extrusion processing I (Carbohydrates)

Raw ingredients significantly affect the quality of final products in extrusion processing, specifically their texture. Carbohydrates, mainly starch, are the most common biopolymer used in making direct-expanded products. The expandability of starch in extrusion makes it the most favorable ingredient for direct-expanded products such as crispy snacks and breakfast cereals. Fiber has been used in the expanded products to add nutritional value, although in many cases it can be a hindrance to expansion. Understanding the behaviors of these raw ingredients under conditions similar to that in extrusion is useful to arrive quickly to the optimum process conditions to obtain products with desired characteristics. This chapter focuses on the behavior of carbohydrates (specifically starch and fiber) during extrusion processing. A brief overview of their chemistry, physicochemical characteristics, transformation under extrusion conditions, and their interactions are discussed.