The Relative Crystallinity, Structure and Gelatinization Properties of Sago Starches at Different Growth Stages

Abstract

The physicochemical properties of starches obtained from various parts of sago palm trunks at different growth stages were reported in a previous paper. Relative crystallinity by X-ray diffraction with calcium fluoride as the internal standard, amylose contents and amylopectin unit-chain distri-butions, photopastegraphy, and differential scanning calorimetry (DSC) of starches were determined. Results obtained were: (1) Relative crystallinity of starch was higher in 14.5-year-old palm than 9-year-old palm, and this also held true for upper part of the trunk as compared to the lower part of the trunk. (2) Amylose content, the total amount of Fr. I, of the starch from the lower part of the trunk was higher than that of the starch from the upper part of the trunk, and increased as the growth period increased. (3) Starch from the 14.5-year-old palm as well as the upper part of the trunk showed lower transmittance curves by photopastegraphy. (4) Gelatinization onset temperature of the starch from the upper part of the trunk ranged from 65.3 to 68.2°C, and gelatinization con-clusion temperature ranged from 75.0 to 76.0°C. Starch from the lower part of the trunk showed lower gelatinization onset temperature and higher gelatinization conclusion temperature compared with that of the starch from the upper part of the trunk.