Effect of the addition of pregelatinized rice starch paste on the retrogradation of rice starch gel

The effect of the addition of pregelatinized rice starch paste (PRSP) on the retrogradation of rice starch (RS) gels was investigated using rheometer, X-ray diffraction (XRD), differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS) and confocal laser scanning microscopy (CLSM). A decrease in the storage modulus of RS gels after short-term storage was found after adding PRSP. The XRD results revealed that the retrogradation degree of RS gels with added PRSP was lower than in the absence of PRSP, suggesting that the addition of PRSP could restrain the long-term retrogradation of rice starch. Moreover, the lower enthalpy changes of RS gels with added PRSP after retrogradation suggested that the progress of amylopectin crystallization was delayed due to PRSP incorporation. SAXS analysis showed that adding PRSP inhibited swelling of RS and decreased the size of aggregation during storage, which suppressed starch retrogradation. In addition, CLSM images indicated that PRSP could form continuous network in which the RS granules embedded, and that gels with PRSP exhibited greater phase separation after 15 d storage. These results suggested that the addition of PRSP inhibited the retrogradation of RS gels. The inhibitory effect is mainly due to PRSP altering the gel formation type and prohibiting the excessive swelling of rice starch granules during gelatinization. This study could provide new insights for the production of rice products and for prolonging their shelf life during storage.