GELATION MECHANISM AND RHEOLOGICAL PROPERTIES OF RICE STARCH

Three rice starches were isolated from indica (KSS7), japonica (TNu67) and waxy (TCW70) varieties, respectively. Amylose contents of isolate d starches were 25.6% for KSS7; 14.80% for TNu67; and 0.99% for TCW70. When heated from 55 to 95 degrees C at 10 degrees C intervals, starch with higher amylopectin content had higher swelling power. Both swell ing power and water solubility index increased with increased temperat ure. The blue values of all samples were <0.08. As examined by scannin g electron microscope and x-ray diffractometer, the typical A-type dif fraction pattern of the peak became slightly flattened at the temperat ure below the gelatinization temperature (GT), and no peak was detecte d at the temperature higher than the GT. The change of starch during h eating or cooling was also analyzed by mechanical spectrometry with an oscillatory rheometer. G' and G '' were dependent on amylose content and starch concentration.