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. Regular and clarified orange juices were concentrated in a four stage, three effect TASTE (thermally accelerated short time evaporator) evaporator. The viscosity of the clarified juice was appreciably lower than that 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 Brix). Flow behavior of orange juice serum tended to be Newtonian. Deviations 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 evaporation rates obtained for serum concentration.