Physicochemical properties, digestibility and expected glycaemic index of high amylose rice differing in length-width ratio in Sri Lanka

Gelatinization, pasting, digestibility and estimated glycaemic index of six high amylose rice varieties differing in length/width ratio were studied. Amylose content ranged narrowly (27.829.1%). Resistant starch content ranged from 0.44% to 1.4%. In contrast to gelatinisation enthalpy, gelatinisation temperature (GT) ranged narrowly (76.777.4 °C). For all rice varieties, melting temperature of amylose-lipid complex I and II was around 99 °C and 110 °C, respectively. The enthalpy of amylose-lipid complex I and II ranged between 0.180.87 and 0.230.55, respectively. Expected in vitro glycaemic index (GI) of all tested varieties was similar (88.292.4). The results showed that the size of the rice grain (length/width) and resistant starch content had no apparent impact on the GI of high amylose rice. The dominant factors determining the digestibility and glycaemic response of the tested high amylose rice varieties seemed to be amylose content and the GT. Besides the pasting temperature, other pasting properties varied significantly but were not correlated to starch digestibility and estimated GI among the six rice varieties. Thus, RVA pasting properties, except for pasting temperature, may not be good predictors for the GI of these high amylose rice