Abstract: In order to explore the affecting mechanism of sodium alginate and calcium chloride on the retrogradation of rice starch, the effect of sodium alginate and calcium chloride on the thermodynamic properties of rice starch retrogradation was investigated using a differential scanning calorimeter and confirmed by thermogravimetric analysis. An Avrami model was used to analyze the kinetic parameters. The results showed that 3 mmol/L calcium chloride, 0.9% sodium alginate and their mixture increased the gelatinization peak temperature by 1.0%, 1.1% and 2.2%, and the gelatinization enthalpy by 4.7%, 14.0% and 21.4%, respectively. There was no significant effect of calcium chloride on the retrogradation of rice starch stored for 21 days (P < 0.05); while 0.6% sodium alginate and its mixture with calcium chloride decreased the retrogradation enthalpy by 23.7% and 27.6%, and the retrogradation rate by 33.9% and 36%, respectively. The crystallization mode of rice starch was transformed from instantaneous nucleation to continuous nucleation in the presence of calcium chloride, sodium alginate (0.9%) or their mixture, and correspondingly, the crystallization rate constant was decreased by 73.0%, 90.1% and 95.3%. The moisture loss rate of retrograded rice starch was decreased by 87.1% with the addition of a mixture of sodium alginate (0.6%) and calcium chloride, confirming the inhibitory effect of the mixture on the retrogradation of rice starch.

Key words: rice starch, retrogradation, sodium alginate, calcium chloride, thermal properties