Molecular and gelatinization properties of rice starches from IR24 and Sinandomeng cultivars

The differences in pasting properties involving gelatinization and retrogra dation of rice starches from IR24 and Sinandomeng cultivars during heating- cooling processes were investigated using a Rapid Visco Analyser (RVA)and a dynamic rheometer. The results were discussed in relation to the molecular structure, actual amylose content (AC), and concentration of the starches, Generally, both starches possessed a comparable AC (approximate to 11 wt%) , amylose average chain length (CL), iodine absorption properties, and dyna mic rheological parameters on heating to 95 degreesC at 10 wt% and on cooli ng to 10 degreesC at higher concentrations. In contrast to Sinandomeng, IR2 4 amylose had a greater proportion of high molecular weight species and num ber-average degree of polymerization (DPn). IR24 amylopectin possessed a lo wer DP, and greater CL, exterior CL (ECL), and interior CL (ICL). Comparing the results of RVA analysis and dynamic rheology, the gelatinization prope rties and higher retrogradation tendencies of IR24 starch can be related to the structural properties and depend on starch concentration. In addition, the exponent n of starch concentration for storage moduli at 25 degreesC ( G'(25) proportional to C-n) increased linearly with increasing AC.