Abstract: In order to find the best drying method for production of turnip chips, the effects of four different drying methods of freeze drying (FD), hot air drying (AD), infrared drying (ID), and explosion puffing drying (EPD) on the physical properties, nutrient composition and microstructure of turnip chips were compared. The nutritional components were determined by chemical analysis, the physical properties were evaluated by a colorimeter and a texture analyzer, and the microstructure was observed by scanning electron microscopy (SEM). Also sensory evaluation was carried out. Furthermore, a comprehensive evaluation was performed using grey correlation analysis based on the coefficient of variation. The results showed that the physical properties and nutrient contents of turnip chips were significantly changed after each drying process. FD and EPD preserved more nutrients. SEM showed that FD chips had a porous honeycomb-like structure; EPD chips also exhibited a more compact honeycomb-like structure and tasted crispy. The comprehensive evaluation revealed that the drying methods were in the following decreasing order: FD > EPD > ID > AD. However, the cost of an FD device and the drying process was higher and the drying period was longer. Taken together, EPD was selected as the optimum processing method for turnip chips.

Key words: turnip, drying methods, nutritional components, microstructure, grey correlation analysis