Concentration of apple juice using a vacuum microwave evaporator as a novel technique: Determination of quality characteristics

This study was evaluated the use of a novel concentration technique, a vacuum microwave evaporator (VME) in the production of clear apple juice concentrate and the investigation of its effects on the quality characteristics of the juice. The optimum processing conditions of the VME for apple juice concentrate were determined using response surface methodology. The apple juice concentrate was produced by VME, a rising film evaporator (RFE), and a rotary evaporator (RE) at the optimum process conditions. The results show that the evaporation rate of VME was three times higher than that of RE and was two times higher than that of RFE. VME produced minimum changes in the color of the apple juices (L*, a*, b*, E, Hue degrees, and C) compared to RE and RFE. VME was also found the best group that preserved the quality characteristics of apple juices (TTA, NEBI, and TPC) compared with conventional evaporation methods.