Rheological behavior of different phases of grape molasses after storage: Effect of concentration and temperature

Abstract

The objective of this study was to investigate the effects of concentration (53, 63, and 73°Brix) and temperature (25, 45, and 65°C) on the rheological behavior of grape molasses after 6 months of storage at the ambient condition (25 ± 2°C). According to the results, a pseudoplastic behavior was observed at different temperatures and concentrations for both red and brown phases of the samples. The power law model revealed the best fit to the rheological data and its parameters (K and n) were determined. After storage, the red phase of grape molasses had different K and n values compared to the brown phase. Furthermore, the influences of temperature and concentration on the K were successfully fitted to the studied model. The flow activation energy (Ea) of grape molasses samples was 20.41–58.53 kJ/mol. A quadratic polynomial relationship was also found between the estimated values of Ea and concentrations with high R2. Practical applications This work aimed to study the effect of concentration–temperature combinations on the rheological behavior of different phases of grape molasses after 6 months of storage. The results demonstrated that the storage period affected the rheological behavior grape molasses. In turn, this change affects the quality of the product. Furthermore, rheological behavior of the samples was well predicted by the studied models. These models describing the combined effect of temperature and concentration on the rheological parameters are very valuable for engineering applications.