Influence of Varying Microwave Power during Microwave-Vacuum Drying on the Drying Time and Quality of Beetroot and Carrot Slices

The aim of this work was to study the influence of microwave power variation during microwave-vacuum drying on both drying time and dried material quality. Red beetroot and carrot were chosen as the material. The quality of the dried material was described by its color change and beta-carotene loss (for carrot) due to drying. The first series of experiments consisted of drying under constant microwave power. Only the lowest microwave power gave an undamaged product. During the second series of experiments, the microwave power was changed in time intervals. However, the use of interval conditions either had a small influence on the process time or did not provide satisfactory quality of the dried samples. During the third series of experiments, initial drying was performed with higher microwave power and then the process was continued with the lowest applied power. This method shortened the process time and gave the best quality of material.