Food extrusion has become a very popular and important processing operation in the food industry. It provides a great opportunity to create new and exciting products. The main purpose of extrusion is to increase the variety of foods in the diet by producing a range of products with different shapes, textures, colours and flavours from basic ingredients. Today, food extruders are used to produce pasta, ready-to eat cereals, snacks, pet food, confectionery products, modified starches for soup, baby food and instant foods, rice and dal analogues, beverage bases and texturized vegetable proteins. Extrusion cooking is a high temperature short-time (HTST) process, which reduces microbial contamination, and inactivates enzymes. A typical extruder consists of a power supply to operate the main screw, a feeder to meter in the raw ingredients, and a barrel, which surrounds the screw. The screw conveys the raw material through towards a shaped hole, the die that shapes the product. Extrusion can take place under high temperatures and pressures or can be simply a non-cooking, forming process. Pre-ground and conditioned ingredients enter the screw where they are conveyed, mixed, and heated by a variety of processes. The product exits the extruder through a die where it usually puffs and changes texture from the release of steam and normal forces. Cereal processing using an extruder offers good opportunities for small-scale businesses in India because raw materials are readily available, extruders are reasonably affordable and if the products are chosen correctly, they have a good demand and can be profitable. The majority of the cereals available in India can be processed with extruder for snacks, pasta, rice analogue or breakfast cereals and combined with potentially hundreds of other ingredients to produce a vast range of processed cereal products.
Abstract published in Quality Assurance and Safety of Crops & Foods 4(3), September 2012. https://doi.org/10.1111/j.1757-837X.2012.00168.x.