Effects of different rehydration temperatures on rehydration and nutritional quality of dried daylily

Daylily is a unique cash crop in China which uses the unopened flower buds as food organs. Fresh daylily easily deteriorates and dried daylily is the main supply form in the market at present. The main goal of this work is to determine dried daylily water rehydration properties and sugar, lignin, cellulose, carotenoid, flavonoid and polyphenol retention properties under different temperatures and time periods. In this study, daylily was soaked at room temperature (25 °C), 50 °C and 70 °C for different durations. The results showed that after rehydration, the brightness index of daylily increased, while the redness and yellowness value decreased. The higher the water temperature, the faster the water absorption expansion rate and the higher the rehydration rate of the dried daylily, but the higher water temperature can cause the destruction of the microstructure of the daylily. The soluble sugars of dried daylily were easily lost in the rehydration process, the contents of lignin, cellulose and carotenoid were relatively stable. The contents of polyphenols and flavonoids decreased significantly with the increase of rehydration time. The rehydration of dried daylily can be carried out at room temperature, and it is recommended that the rehydration time take 0.5 h.