Optimization of Ultrasonic-thermal Concentrator Performance under Vacuum Conditions in Watermelon Juice Concentration Process

Document Type : Research Paper


1 Department of Biosystems Engineering, Faculty of Agriculture, Bu Ali Sina University, Hamedan, Iran

2 Department of Biosystems Engineering, Faculty of Agriculture, University of Bu Ali University, Hamedan, Iran.

3 Department of Food Science and Technology, Faculty of Agriculture, Tarbiat Modares University


  In this study, an ultrasonic-thermal concentrator under vacuum conditions was fabricated and the effect of concentration variables for watermelon juice concentration was optimized. Concentration temperature process in three levels (40, 50 and 60°C), vacuum pressure in three levels (20, 40 and 60kPa) and ultrasonic waves power in three levels (36, 60 and 84W) were conducted. Statistical analysis of data and optimization of concentration process were performed using response surface method and central composite design. Results showed that the increase of concentration temperature has a positive effect on concentration process time and total energy consumption and negative effect on lycopene content and the total color difference. Decrease of vacuum pressure to caused increased lycopene content and decrease the total color difference, concentration process time and total energy consumption. Also increased ultrasonic waves power caused increase in lycopene content, total color difference, total energy consumption and decrease in concentration process time. Optimization of watermelon juice concentration point was obtained on concentration temperature 40°C, vacuum pressure 20 kPa and ultrasonic waves power 46.5W. Optimal values of response variables in this condition include lycopene content, the total color difference, concentration process time and total energy consumption in equal order 238 mg/kg, 25.7, 94.5 min and 0.727 kWh. The use of ultrasound waves along with the concentration temperature and vacuum pressure could have positive results on the watermelon juice concentration process.


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