Document Type : Research Paper
Department of Food Science and Technology, National Nutrition and Food Technology Research Institute, Faculty of Nutrition and Food Technology, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Department of Food Technology, College of Abouraihan, University of Tehran, Pakdasht, Iran
Department of Agrotechnology, College of Abouraihan, University of Tehran, Pakdasht, Iran
Grapefruit juice contains a large number of nutrients that should be preserved during processes such as concentration. In the present study, osmotic distillation (OD) was used to concentrate this juice compared to the thermal process. The extracted juice was centrifuged (2000 rpm, 5 min) and osmotic distillation was performed in a laboratory scale flat sheet module by PVDF membrane (0.22 µm). After evaluation of osmotic pressure of 40 salts, AlCl3 and LiCl were selected because of their high potential to produce osmotic pressure, and the volumetric rates of the brine and the juice were 0.6, 1.3 and 2 mL.s-1. Thermal concentration was done in a rotary evaporator at 70˚C to 30 °Brix to compare the changes in physicochemical properties. The results showed that the low flow-rate of brine and juice was more effective during OD. It was also concluded that concentration of grapefruit juice with AlCl3 and LiCl was more efficient than concentration with CaCl2. The vitamin C content did not significantly change comparing to 40% decrease in thermal concentration. Also, polyphenol content increased after OD but did not change significantly after thermal concentration. The antioxidant activity and pH were constant in both concentration methods. The total acidity of fresh juice increased by about 23% after OD, but it remained constant with thermal concentration. Juice turbidity increased after both concentration methods.