Rheological and functional properties of Roselle (Hibiscus sabdariffa) leaves puree

Pureed form of leaves (Hibiscus sabdariffa L. (Roselle)) was taken for physicochemical and rheological analysis at temperatures and TSS range of 278 K - 318 K and 3 - 5 °Brix respectively. The steady-state rheological analysis was performed with a shear rate of 1 - 100 s-1. Different rheological models are tried; Power-law was best fitted with the experimental data (R2 ≥0.98). Temperature dependence of viscosity was found out using an Arrhenius-type relationship at a shear rate of 10, 50, 100 s-1 IR analysis was done to know the influence of functional groups on rheological properties of purees. Consistency index (K) of puree increases with increase in TSS content but at a fixed TSS, there is a decrease in K with an increase in temperatures but the opposite was observed for flow behavior index (n). Puree showed a shear thinning behavior with an increment in temperature level and puree having 5 °Brix (8.37) has higher activation energy (kJ.mol-1) than 3 °Brix (6.32).