Modeling the kinetics of extracting oleoresin from dried turmeric (Curcuma longa L.) rhizome using acetone as solvent

• Time to reach equilibrium state in a batch operation (Soxhlet extractor) is studied.
• The kinetics of extracting turmeric oleoresin using solvent extraction (Soxhlet extractor) is studied.
• A first order kinetic model gave good fit to experimental data.
• Effect of operating conditions on equilibrium time, kinetics and model parameters is studied.

Kinetics of extracting/leaching (solid–liquid extraction) oleoresin from dried turmeric (Curcuma longa L.) powder was studied to determine the time taken to reach the equilibrium state. Acetone was used as solvent and the extraction was carried out at temperatures ranging from 35 °C to 50 °C using solid-to-solvent ratios between 1/5 and 1/30 (g/g). Equilibrium time was affected by temperature but not by the solid-to-solvent ratio. Results suggest that the increase in oleoresin yield was insignificant after 60 min of extraction time. A highest oleoresin yield of 6.49% (db) was obtained at 50 °C with solid-to-solvent ratio (1/30). A non-linear regression model was fitted to represent the kinetics of oleoresin yield. Effect of process variables (temperature and solvent-to-solid ratio) on model parameters, k (maximum possible extraction, percent dry basis) and a (initial extraction rate as a fraction of k – under specified conditions) were also studied. Equilibrium time is used to reduce lengthy extraction time.