EFFECT OF TEMPERATURE AND CONCENTRATION ON RHEOLOGICAL PROPERTIES OF CAROB JUICE

Abstract

A study on the rheological behaviour of carob juice was carried as a function of solid concentration, in the range 25-45 degrees Brix, at different temperatures (20-60 degrees C), with a rotational viscometer. The viscosity decreased with an increase in temperature. Using Herschel-Buckley model, both flow behaviour index (n) and consistency index (K) were determined. The calculated values of flow behaviour index were less than 1 at all temperatures and concentrations. Therefore, the carob juice was well described by the Pseudoplastic behaviour. The Herschel-Buckley model represented well the rheological data, with high values for the determination of coefficient (R-2). The effect of temperature on viscosity was evaluated by using an Arrhenius type equation. The activation energy (E-a), at a shear rate of 12.2 s(-1), was found in the range of 1.77-10.25 kJ/mol.