EXOTHERMIC TRANSITIONS ON COOLING OF GELATINIZED NATIVE RICE STARCH STUDIED BY DIFFERENTIAL SCANNING CALORIMETRY

Differential scanning calorimetric (dsc) experiments were designed to investigate the exothermic events on programed cooling of gelatinized native rice starch-water system. these exothermic transitions, with peak temperatures of 85°c–127°c, were attributed to amylose-lipid complexes recrystallization. starch concentration and cooling rate showed significant effect on the manifestation of these transitions. the 1:1 starch to water ratio system showed broader and flattens exothermic transitions at higher peak temperatures (120°c–127°c) which were stable over different cooling rates. on the other hand, the 1:2 and 1:3 starch to water ratio systems showed sharpen and narrow exotherms at lower peak temperatures (85°c–100°c) which became smaller with lower cooling rate. these observations suggest the presence of two types of amylose-lipid complexes in native rice starch-water system.