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 °Brix, at different temperatures (20-60 °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 (R2). The effect of temperature on viscosity was evaluated by using an Arrhenius type equation. The activation energy (Ea), at a shear rate of 12.2 s-1, was found in the range of 1.77-10.25 kJ/mol.