The effect of xanthan on short and long-term retrogradation of rice starch

The short‐term retrogradation of the rice starch (RS)/xanthan (Xan) mixtures was investigated by Brabender‐E viscograph and dynamic rheometer while the long‐term retrogradation was investigated by DSC and pulsed NMR (PNMR), respectively. RS and 0, 2.5, 5, and 10% Xan (based on RS weight) were prepared into RS/Xan mixtures at the ratios of 100:0, 40:1, 20:1, and 10:1 w/w, respectively. With increasing Xan concentration, the reduced setback (SB) value suggests the decrease of short‐term retrogradation. The gelation rate constant (k) of the mixtures increased during the storage at 4°C for 5 h due to phase separation. The endothermic enthalpy of the pastes of RS/Xan mixture after being stored at 4°C for 1, 3, 5, 7, 14, and 21 days were lower than the native starch stored for the same days. The spin–spin relaxation time (T2) indicating the water mobility of starch gels was detected. T2 decreased gradually with extending storage time, which may be attributed to the retrogradation of RS. T2 of the system with xanthan was apparently higher than that without. The overall results demonstrate the remarkable inhibitory effects of Xan on the retrogradation of RS.