VISCOSITY CHANGES IN ORANGE JUICE AFTER ULTRAFILTRATION AND EVAPORATION

Suspended solids, including cloud and pectin, were removed from orange juice using a hollow fiber ultrafiltration membrane (500 kDa). Orange juice serum had a clear amber color with no measurable turbidity. Reg ular and clarified orange juices were concentrated in a four stage, th ree effect TASTE (thermally accelerated short time evaporator) evapora tor. The viscosity of the clarified juice was appreciably lower than t hat of regular juice, i.e. 15.55 mPa for serum and 164 mPa (at 100 s(- 1)) for regular orange juice concentrate (65 degrees C, 66.5 degrees B rix). Flow behavior of orange juice serum tended to be Newtonian. Devi ations from Arrhenius behavior were found for changes in viscosity of orange juice with temperature. Reduction in viscosity of orange juice increased heat transfer coefficients as reflected by the higher evapor ation rates obtained for serum concentration.