Puffed grain snacks have been made for centuries with the simplest methods like popping popcorn. Modern puffed grains are often created using high temperature, pressure, or extrusion.
Products such as certain pastas, many breakfast cereals, premade cookie dough, some french fries, certain baby foods, dry or semi-moist pet food and ready-to-eat snacks are mostly manufactured by extrusion. It is also used to produce modified starch, and to pelletize animal feed.
Generally, high-temperature extrusion is used for the manufacture of ready-to-eat snacks. The processed products have low moisture and hence considerably higher shelf life, and provide variety and convenience to consumers.