Hydrophobic Al2O3 membranes were prepared by grafting C6F13C2H4Si(OC2H5)(3) molecules, and then applied to a vacuum membrane distillation (VMD) system for concentration of sucrose solution as a model solution of fruit juice. The effects of sucrose concentration and solution temperature on the VMD performance were discussed. By exposing the surface side of the tube membrane to an aqueous solution of 10 wt% sucrose at 60 degrees C and applying vacuum at the inner side of the Al2O3 tube to a pressure of 0.5 kPa, permeation flux of over 7 kg m(-2)h(-1) was attained through the hydrophobic Al2O3 membrane with asymmetric structure. A mathematical model based on Knudsen and Knudsen-viscous models revealed that the permeance of the asymmetric membrane depends on that of the substrate layer, due to its thickness of 1.47 mm.