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*, ΔE, Hue°, and ΔC) 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. Practical applications: Microwave heating provides volumetric heating of food. The concentration carried out quickly with the combined system, microwave and vacuum, which allows mass and energy transfer quickly at a short time. The physicochemical, and biochemical properties of the concentrated apple juices processed using VME were found to be better than those of the juices produced using the other conventional methods. The obtained data can be useful for optimization of fruit juice concentrate production in industrial concentration processes.