Microwave dryers decrease the drying time but they have significant effect on the quality of the end product. You should consider convective dryers assisted with solar energy for better quality and less energy use. Heat pump dryers also is an alternative. Moreover, freeze-dryer is the best option to preserve quality properties but they have very small load capacity in comparison with others. So, it is not a good choise for industrial applications. It can be used to dry valuable products.

I think the success of the drying depends on the fruit type, particle size, the enduse of the dried product and the production costs associated. To answer your question with fair degree of confidence, indepth literature review or even some applied research may be required for the fruit types of your interest. From research experiences, Freeze-drying is the best in terms of retaining the nutrients and structure of the fruits. Fluid bed drying may also be one of the good air drying processes if uniform particle size can be maintained. Good Luck!

I think I should think about using Pulsed Electric Fields technology combined with oven drying. It has been shown that Pulsed electric field improves the drying speed of various fruits as well as the quality of the final product obtained.