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.

Coconut inflorescence sap (CIS) is sweet, oyster-white and translucent and was reported to be highly nutritive and a good digestive agent. The chemical composition changes including total sugar, reducing sugar, ethanol, total acidity, volatile acid, amino acid, vitamin C and total phenolic contents of postharvest coconut inflorescence sap (PCIS) were investigated during a 12-day natural fermentation, and the variety and content of phenolic compounds of fresh coconut inflorescence sap (FCIS) and natural fermented coconut inflorescence sap (NCIS) were also studied by an high performance liquid chromatography (HPLC) system. Total acid, volatile acid and total phenolic contents increased during natural fermentation, while total sugar contents decreased during natural fermentation. The amino acid content declined steadily after harvesting until 3 days, but then remained almost constant. Vitamin C content decreased on day 1, slowly rose to 20.7 mg/L on day 3, and then decreased obviously. Five kinds of phenolic compounds were detected by HPLC. These compounds all increased in NCIS compared with FCIS; both NCIS and FCIS also contained other kinds of phenolic compounds.

No abstract