Optimization of Rotary Vacuum Drying Conditions of Lily-Slice

The rotary vacuum drying of lily was analytically calculated in quadratic polynomial regression equation,derived in Box-Behnken experimental design,and experimentally evaluated.The influence of the conditions,including the temperature,pressure and rotation-rate,on the quality of dried lily was investigated.The results show that the drying conditions all had a major compact with descending order:drying-temperature ≌ drying-pressure>rotation-rate;and that the rotary vacuum-drying outperforms the hot-air and vacuum-freeze drying techniques.Specifically,the VC-content changed in an increase-decrease mode with the increases of temperature/rotation-rate or with a decrease of pressure.Dried at 70℃/0.08 Mpa/80 r/min for 5.5 h, the dried lily slice with the optimized quality has VC-content of 13.98 mg/100 g, rehydration ratio of 2.01 and chromaticity difference of 9.26.