Changes in rheological properties of koruk (unripe grape) juice concentrates during vacuum evaporation

The time-dependent and time-independent rheological properties of koruk juice (unripe grape juice) concentrates were determined over a wide range of temperatures (10-80°C) and concentrations (4.6-25.0% soluble solids contents, SSC). Power-Law model was the best model describing the time-independent rheological behavior of unripe grape juice. Apparent viscosity of concentrates decreased with an increase in temperature for all concentrations. The flow activation energy for the consistency coefficients and the apparent viscosity of unripe grape juice concentrates were 40.70 and 13.54 kJ/mol, respectively. The time-dependent thixotropic energy of unripe grape juices decreased as the temperature increased.