Application of Extrusion Technology in Food Processing: A Review

Abstract

Extrusion technology is a high-temperature short-time processing approach used to transform starchy and proteinaceous food materials into structured products through controlled pressure, temperature, moisture and mechanical shear. This review examines the operational principles of food extrusion and describes the main processing systems, including hot and cold extrusion and single-screw and twin-screw extruders. It also outlines the major mechanical components of an extruder, from pre-conditioning and feeding systems to the die and cutting mechanism, and summarises the key pre- and post-extrusion steps involved in product development. The review further discusses the physical and functional changes that occur during extrusion, including colour development, expansion, water hydration, hardness, starch gelatinisation, protein denaturation, lipid modification, dietary fibre redistribution, vitamin stability and reduction of antinutritional factors. Applications across food sectors are considered, including breakfast cereals, confectionery products, meat analogues, pasta, snacks, baby foods, pet foods, animal feeds and value-added products from food wastes and by-products. Recent developments, including hot-melt extrusion, supercritical-fluid-assisted extrusion, extrusion-based 3D printing and low-temperature extrusion for ice cream, are also reviewed. Overall, extrusion technology is presented as a flexible and resource-efficient process that supports product diversification, improved functionality, microbial safety, nutritional improvement and sustainable use of food-processing by-products in contemporary food systems.