Optimization of microwave vacuum drying of lotus (Nelumbo nucifera Gaertn.) seeds by response surface methodology.

摘要

Drying is the main process used to treat lotus seeds for storage. In this study, response surface methodology was used to optimize processing methods for microwave vacuum (MWV) drying of lotus seeds and to create a desirable product. A central composite design with 3 important factors, namely microwave output power (2.0-4.0 kW), vacuum degree (--0.070 to --0.090 MPa) and on/off ratio (68/52 to 99/21 s), was used to study the response variables of drying time, shrinkage ratio, rehydration ratio and whiteness index. Optimal conditions for MWV drying of lotus seeds were determined to obtain a min. drying time, min. shrinkage ratio, max. rehydration ratio and max. whiteness index. The optimum drying conditions were found to be: microwave output power 3.2 kW, vacuum degree --0.083 MPa and on/off ratio 94/26 s. Under these conditions, drying time, shrinkage ratio, rehydration ratio and whiteness index were found to be 10 min, 37.66%, 157.1% and 68.83, respectively.