Engineering Review Food Extrusion Technology and Its Applications

Abstract

An extensive technical review of studies on food extrusion processes which involves forcing mixed food ingredients through a die to produce food snacks has been carried out in this paper. This technical review includes some historical development, food extruder types, extrusion principles and applications, flow simulation and heat transfer modeling in extruders, process parameters and product quality, extruder die and extrudate expansion among others. The research and application of extrusion in food industry was mainly based on the adaptation of plastic extrusion technology which has been in existence for over hundred years. Studies show that twin-screw extruder are more efficient than single-screw extruders because of better mixing and better handling of different combinations of food ingredients. A thorough knowledge of the flow and heat behavior inside an extruder provide an insight into the mechanism of mixing and facilitates estimation of RTD, flow rate, pressure drop, heat transfer mechanism and power consumption. Until recently, very little work has been published on the mechanism of material flow and energy transfer in intermeshing co-rotating extruder mainly due to the complexity of the geometry and the flow behavior. A more recent approach to research in modeling of food extrusion is the 2D or 3D flow modeling using finite element computer package. This research area is gaining recognition in modeling different sections of food extruder. This work also points out some of the achievements and shortcomings of the reviewed works and where necessary, possible solutions are suggested. Areas needing further research have been highlighted. This study will reveal that understanding and application of extrusion technology in developing countries of Asia and Africa are still far from being satisfactory and this work would serve as a good reference material for researchers and operators in food extrusion technology.

Effect of Die Configuration on the Physico-Chemical Properties, Anti-Nutritional Compounds, and Sensory Features of Legume-Based Extruded Snacks

“…The star-shaped cross section is characterized by the presence of angles, absent in the circular one, which could have caused a mechanical breaking of bubbles in the gelatinized starchy matrix flowing through the die, further disturbing the expansion of the extrudate. The increase in the die nozzle diameter was found to cause a decrease in radial expansion in yellow corn extrudates [ 39 ]. A higher extrusion pressure also induces a higher degree of starch gelatinization [ 39 ], as was observed in the spherical extrudates, compared with the star-shaped ones, except for the red lentil-based products, due to their high fiber content.…”

“…The increase in the die nozzle diameter was found to cause a decrease in radial expansion in yellow corn extrudates [ 39 ]. A higher extrusion pressure also induces a higher degree of starch gelatinization [ 39 ], as was observed in the spherical extrudates, compared with the star-shaped ones, except for the red lentil-based products, due to their high fiber content. The presence of the fiber, in fact, restricted the starch gelatinization required for the expansion of the expanded snacks [ 40 ].…”

Moisture Sorption Behavior of Deproteinized Sunflower Meal and Patterned Food Extrudate

“…A single-screw [27] laboratory extruder (Brabender 20 DN, Duisburg, Germany) was used for the extrusion process. The extrusion parameters (working screw speed 200 min −1 ; feed screw speed 30 min −1 ; nozzle's inner diameter 4 mm; temperatures in each of the zones in the extruder 130 • C, 150 • C, and 160 • C; screw compression ratio 3:1) were described in our previous investigation with deproteinized rapeseed meal [28].…”

Food Extrusion Technology: Initiatives to Address Food and Nutrition Insecurity in South Africa

“…Extrusion is thermo-mechanical, high temperature, short time processing technique. Food extrusion is whereby raw materials of low or high moisture content are chemically modified and transformed into an extrudate [13][14][15][16][17][18]. The food extrusion process is simply cooking of dry raw materials by steam.…”

“…After compression the dough is conveyed towards the die. At the die section (barrel end) the dough expands and is cut by blades into the products or extrudates of varying shapes and sizes [13,18]. Extrusion technology dates back almost 200 years ago (a historic timeline is depicted in Figure 1).…”