Food extrusion technology

Food extrusion can be defined as a process of mixing, homogenizing, and shaping low moisture food materials and more recently high moisture food materials are forced through an opening or die with a design specific to the food, and is then cut to a specified size by blades.

Extrusion cooking is a versatile and very efficient technology in food processing. The process is a high-temperature short-time (HTST) process which inactivates enzymes and reduces microbial contamination. Extrusion cooking is mostly preferred, as it has high productivity and significant nutrient retention as compared to conventional cooking.

While food is being forced through the extruder, the food mix is thermomechanical cooked to a high temperature (usually in the range 100°C–180°C), pressure and shear stress that are generated in the screw-barrel assembly.

The laminar flow within the channels on the extrusion screw and extruder die aligns the molecules in the direction of flow to create the crunchy or chewy texture in fabricated food.

Extrusion cooked melts transit from high pressure to low (atmospheric) pressure when they exit the die. The extrudates generally require no further processing except for some minimal drying.

The entire process is continuous and capable of happening in less than a minute. The most common used extruders in the food industry include single-screw and twin-screw systems, with twin-screw systems more widely used because of their flexibility.

Extrusion brings gelatinization of starch, denaturation of proteins, reduces lipid oxidation and anti-nutritional factors. In addition, it is considered a versatile, low cost and very efficient technology in the food processing.
Food extrusion technology