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Changes in Retrogradation Properties of Rice Starches with Amylose Content and Molecular Properties

¹Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan. ²Graduate Institute of Food Science and Technology, National Taiwan University, Taipei 10764, Taiwan. ³Dept. of Food and Nutrition, Providence University, Taichung 43301, Taiwan. ⁴Corresponding author. E-mail: mflai@pu.edu.tw

The increases in storage modulus (G′), retrogradation enthalpy change (ΔH) and ΔH-related Avrami kinetic parameters of gelatinized rice starch dispersions at 25% (w/w) were investigated with respect to storage period, amylose content (AC), and molecular properties. Three high-AC and five low-AC rice cultivars were compared for understanding the multiple influences of AC and molecular properties involved. After refining the results of correlation analysis, the G′ of just-cooled samples changed positively, mainly with AC and additionally with the average chain length of amylose (CL_AM) and the weight ratio of extra-long plus long chains to short chains of amylopectin (AP) (r_APchain). The developed ΔH on short-term storage (10 days) elevated with increasing AC and CL_AM and decreasing degree of polymerization of AP (DP_AP), but after long-term aging for one to three months with increasing r_APchain, especially for the low-AC cultivars examined. Greater Avrami rate constants for retrogradation could be attributed to the combination of a lower DP_AP and r_APchain or AP chain length and a greater CL_AM. The polynomials using these critical factors to describe the retrogradation parameters were elucidated and could account for 85–99.6% of data deviations.