Rheological behaviour of concentrated mandarin juice at low temperatures

摘要

Several rheological properties of concentrated mandarin juice were investigated, quantifying thixotropic behaviour and fitting experimental data to the Hahn, Weltman, and Figoni-Shoemaker equations. The latter one proved best for modelling the time dependency response. Pseudoplastic behaviour fitted well with the Herschel-Bulkley model in the interval between -12 and 6℃, in which yield stress and the flow behaviour index scarcely changed with temperature. The consistency coefficient and apparent viscosity both decreased as temperature increased. Fitting these consistency data to the Arrhenius-type equation, a value of 33 kJ mol~(-1) for activation energy was obtained. Concentrated mandarin juice displayed viscoelastic properties in the temperature range between -12 and 6℃, with the elastic character (determined by the juice's pectin content) predominating over the viscous nature at low frequency values, but with this behaviour being inverted for high values. Furthermore, as the temperature became higher, the elastic character became more important than the viscous nature.