Rheological Behaviour and Time Dependent Characterisation of Gilaboru Juice (Viburnum opulus L.)

Abstract

The flow curves and time-dependent rheological behaviour of gilaboru ( Viburnum opulus L.), a traditional drink in the middle Anatolia region of Turkey, with different solid concentrations (59.7, 56.3, 53.1, 43 and 35°Brix) were studied at different temperatures (5-60°C) using a controlled stress rheometer. Gilaboru samples exhibited thixotropic behaviour for all concentrations, both in the forward and backward measurements were characterised by the power law. A single equation was proposed for the apparent viscosity 1. Temperature played a major role in determining the magnitudes of the apparent viscosity 1. The completely destructed gilaboru samples flow curves were also measured after subjecting the samples to a high shear rate for 2h. After eliminating thixotropy by shearing, samples showed shearthinning properties that fitted well to the power law model. Three models were used to describe the time-dependent behaviour, namely, the second-order structural kinetic, Weltman and first-order stress decay models. Among the models, the first-order stress decay model fitted well compared to the second- order structural kinetic and Weltman models.