FLOW BEHAVIOR OF CLARIFIED ORANGE JUICE AT LOW TEMPERATURES

This paper presents a study of the rheological behavior of clarified and depectinated orange juices, with different soluble solid contents, at temperatures just above their freezing point. The rheological behavior of depectinated and clarified orange juice was determined for a wide range of soluble solid contents (10-65.8 degrees Brix) and temperatures (-15 to 30C). The results indicated that the samples behave like a Newtonian fluid. The effect of temperature on the juice can be described with an Arrhenius-type equation. It was found that the activation energy for viscous flow was in the range of 9.4 to 59 kJ/mol, depending on the concentration. The effect of the soluble solid content can be described by an exponential-type equation. Finally, an equation in which dynamic viscosity depends on temperature and soluble solids content gives the following expression: eta = 1 x 10(-15) exp(0.12C + 9021/T), where T in Kelvin, C in degrees Brix, and viscosity in mPa center dot s. PRACTICAL APPLICATIONS It is necessary to know the relationship between viscosity with temperature and concentration, since knowledge of these parameters is of vital importance in the manipulation, calculation and design of all those unit operations during the process, mainly those based on heat and quantum transfer.