Rheological behavior of sour cherry juices concentrated by ohmic and conventional evaporation processes under vacuum

摘要

In this study, sour cherry juice was evaporated up to 65% total soluble solid content (TSSC) under vacuum (25 kPa) by ohmic-assisted vacuum evaporation (OAVE) and vacuum evaporation (VE). The effects of voltage gradients (10–14 V/cm) on the rheological behavior of sour cherry concentrates having different TSCC (30%–65%) were determined, and compared with those of VE. In general, the shear stress increased as the shear rate increased for all concentrations. Since the statistical error values of Power Law and Newton models were similar (p＞ .05), the most appropriate model describing the rheological behavior was chosen as Newton model being more nominative and mathematically simpler. The viscosity of concentrates (30%–65%) varied in the range of 0.003–0.119 Pa.s. The increase in the viscosity values depending on TSSC during evaporation was similar for both processes. Thus, OAVE could be beneficial alternative method to VE for the purpose of producing fruit juice concentrates having similar rheological properties.