Technology Advance on Drying Taro Slices by Using a Combination of Hot Air and Microwave Vacuum

Drying is an important and widely-used method for food processing. However, it is probably the most energy-intensive procedure of the major industrial processes and accounts for up to 15% of all the energy usage during the production; and quality of dried food is another important issue during the food drying. Single-stage drying technology cannot guarantee the fulfillment of stringent requirements for quality products and lower energy consumption. New drying technologies advance in recent years that employ integrated multiple stages of heat transfer and package methods.

Recently, Prof. Dajing Li’s team in the Institute of Farm Product Processing, Jiangsu Academy of Agricultural Sciences, found that the combination of hot air and microwave vacuum can improve efficiency during the drying of taro slices to enhance food quality, reduce energy consumption and reduce processing time. The new technology improved both the moisture diffusivity and mass transfer coefficient of taro slices. Dried taro slices exhibited significant improvement of hardness value, crispness value, color, puffing rate, nutritive value and sensory quality.

In addition, the nutritional compositions and their changes among different varieties of taros during drying process have been studied by applying the combination of hot air and microwave vacuum. We observed that the new technology resulted in much less starch but little loss of nutrition. The quality of different taro varieties showed significant differences during the process. Lipu taro, Longxiang taro, Fenghua taro, Pinang taro and Xiangsha taro had high brightness value and little color change. Longxiang taro and Wugu taro exhibited porous structure, high puffing rate, moderate hardness and good crispness. Sensory evaluation showed that Longxiang taro, Fenghua taro and Wugu taro had better color, shape, texture, sensory quality and acceptable level than that of the other taros. The research paper titled “Quality Changes of Different Varieties of Taro using Microwave Vacuum Drying” will be published on the first issue of Journal of Modern Food Science and Technology of 2016.


                                                 Figure 1. Hardness and crispness of different varieties of taro

                                      during the drying process by combination of hot air and microwave vacuum


                                                Figure 2. Microstructure of different varieties of taro

                                      during the drying process by combination of hot air and microwave vacuum