ICAR Research Data Repository for Knowledge Management

Extrusion cooking is one of the most promising techniques in the field of food technology developed in the recent times. Its advantages are many, which have been well documented in the literature. However, practice of this technology, has remained more an art than the science. Knowledge and database on extrusion cooking is however growing fast. Extrusion cooking is associated with partial or complete gelatinisation of the starch, complex formation, transformation and interactions involving bio-polymers. Of the two types of extruders (single screw and twin-screw), twin-screw extruder permits a greater flexibility of operation to achieve the desired time, temperature, and shear range for the processed material because of an additional independent variable, viz., screw configuration. Understanding the extruder behaviour and material flow during extrusion cooking is essential to the design of automation and control systems. Some models have adapted from plastic extrusion with modifications that account for the differences of foods from plastics. Cereal grains lend themselves as good raw material for preparation of ready to eat snack foods and other products on account of high starch content in them. Extensive work has been reported on extrusion of corn (maize), in comparison to that for wheat and rice. The latter is of significance to India and other Asian countries. Rice is a popular, nonallergic, glutenfree source of carbohydrate, vitamins, and minerals with little fat. With an annual production of over 120 million tonnes of paddy, rice is the largest crop produced and consumed in India. It is the major supplier of energy, protein and other nutrients in the diet of more than half of the Indian population. Apart from being consumed as whole grain for table purposes in the form of raw milled rice or parboiled milled rice, a considerable quantity of paddy is also converted into many traditional products. Extrusion cooking could give products similar to the traditionally prepared expanded or puffed rice products with advantage of being more hygienic and economic process. However, literature on twin-screw extrusion cooking of rice is rather scanty. The present study was, therefore, undertaken to screen a larger number of extruder and extrusion variables, and to study their effect on the system parameters during extrusion processing of rice flour, and the quality of resultant extruded products in terms of physical, physicochemical, molecular and functional properties.