Increasing heating performance and preservation of product quality are critical factors in the food industry. Although microwave-vacuum heating is applied in many food processes, there are many unanswered questions about its effects on sensitive foods. In this study, the tomato juice was concentrated in microwave-vacuum heating system and results compared with conventional and conventional-vacuum heating methods. The effect of pressure and microwave power was investigated on quality parameters, energy consumption, exergy performance, and processing kinetics of tomato juice concentration. The processing time in the microwave-vacuum method was 2.3 to 6.3-fold lower than conventional and conventional-vacuum methods. The exergy performance was obtained in the range of 7.16–13.29% for microwave-vacuum heating and 2.04–2.99% for conventional methods. Microwave vacuum heating could reduce energy consumption by 30–71%, compared with conventional-vacuum methods. The minimum decline in ascorbic acid and total phenol content of tomato juice concentrate was observed for microwave-vacuum evaporation. Microwave-vacuum heating was an excellent concentration technique that provided tomato paste with improved nutritional quality, increasing exergy efficiency, reducing processing time and energy consumption compared to conventional and conventional vacuum processes.
