Influence of three different drying techniques on persimmon chips' characteristics: A comparison study among hot-air, combined hot-air-microwave, and vacuum-freeze drying techniques

The effect of three different drying methods (hot-air, combined hot-air-microwave, and vacuum-freeze) on the sensorial, textural, nutritional, and other quality characteristics of persimmon chips was compared. The result showed that the freeze-dried chips had the best nutritional and quality features. However, persimmon chips processed by combined hot-air-microwave and freeze-techniques had the same sensory score (85.40 points), which were higher than that of hot-air dried samples (70.51 points). Additionally, persimmon chips dried with aid of hot-air technique had the lowest chewability value and hardly met the panelists' requirements. These disadvantages could be avoided by using a combined hotair-microwave drying method with lower power consumption compared with the others. The optimized combining microwave and hot-air drying conditions were as follows: 1 mm thickness of persimmon slice, a temperature of 70 degrees C at an air velocity of 1.0 m/s of initial hot-air drying system until the moisture content of persimmon samples reached 10% (about 150-160 min) and 10.7 Wg(-1) of the following microwave-drying system. It was concluded that the combined hot-air-microwave drying technique could be used for processing persimmon chips with high quality and nutritional values as well as low operating costs. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.