Production of some Snack Foods by Extrusion Processing of some Cereals and their By-products

摘要

Background: Extrusion industry is a process in which raw materials are forced to flow under various conditions of moisture content , temperature and extruder screw speed. Several types of raw materials were used in this industry. In the present study broken rice which considered as a by-product of rice whitening industry and semolina were studied as raw materials for extrusion industry. Materials and Methods: Various conditions of moisture content , temperature and screw speed were studied. Results: Obtained results of physical characteristics of the products showed a relation between expansion ratio and specific weight of extruded materials i.e., the greater the expansion volume, the lower the specific weight. The optimum conditions obtained for the lowest specific weight of broken rice and semolina flours were 15% moisture content , 130°C and 150 rpm for extruder screw speed. The same conditions were found to obtain the best shear force for broken rice and semolina. The Water Solubility Index (WSI) and Water Absorption Index (WAI) for extruded broken rice and semolina showed that the maximum values of WAI and WSI were obtained at 15% moisture, 170°C and 150 rpm for extruder screw speed. Broken rice flour had the lowest value of cooked-paste viscosity at 50°C after coding while semolina extrudate had the highest value of the cooked-paste viscosity. Conclusion: Thus broken rice and semolina could be considered as suitable materials for extrusion technology.