|
Effect of different mixing ratio of non-glutinous and glutinous rice on physical and rheological properties of extrudate prepared in a single screw extruder were examined. The extrusion conditions in term of screw speeds, moisture content and die temperature were 258 rpm, 18% and 120℃ , respectively. The resisdence time distribution of the most of materials were within 30 second and small portion of them went up to 80 second. The expansion ratio was the highest value (2.93) for 70% of glutinous rice in the mixture, while the lowest value for 100% of non-glutinous rice. Breaking strength was in the range between 1,0518 and 1,117g for 10∼20% of glutinous rice in the mixture, while the lowest value (7378) for 80%r of glutinous rice. As the amount of glutinous rice increased, L and a values were increased and b value was decreased. The uncooked cold paste viscosity had 400 B.U. for 100% non-glutinous rice , while no peak for the 100% glutinous rice. As the amount of glutinous rice increased up to 100%, the water absorption index (WAI) was decreased, while water solubility index (WSI) was incrersed. The rheological properties of extrudate were accounted by the law of Oswald. The flow behavior index of extrudate was less than 1.0, which showed pseudoplastic behavior. Yield stress was the h,ghest value for 20%r of glutinous rice in the mixture and the lowest value for 80∼100% of glutinous; rice. Number of air cell was between 128 and 159 for 80∼100% of glutinous rice in the mixture, while 81∼84 for 0∼20% of glutinous rice. The degree of shapefact was increased more when the mixtures of glutinous and non-glutinous rice was used than when glutinous or non-glutinous rice was only used.
|