Rheology of sea buckthorn (Hippophae rhamnoides L.) juice

Abstract

Juice extracted from sea buckthorn fruits was subjected to dynamic rheological measurements in a controlled stress rheometer. Sea buckthorn juice exhibited wide variations in flow behavior from pseudoplastic to dilitant with increasing temperature. The power law model suitably (r >/= 0.975, P</= 0.001) described the shear-stress versus shear-rate data of the juice. Changes in apparent viscosity of the juice with increasing temperature obeyed the Arrhenius law at shear stress above 1 Pa but deviated from it at low shear stress of 0.1 Pa. The rheological behavior of sea buckthorn serum obtained after centrifugation of the juice was similar to those of the juice and sucrose solution at high shear rate but differed from them at low shear rate. Addition of ethanol insoluble substances up to 7% (w/v) to the juice changed its rheological behavior to resemble that of a sea buckthorn juice concentrate at 48 degrees Brix, although frequency dependence was unaffected above 1 Hz. Sea buckthorn juice was found to be thermostable within the temperature range from 25 to 70 degrees C, although critical changes occurred in juice components above 70 degrees C.