Optimization of Oleoresin Extraction from Curcuma longa L. Using RSM and Determination of Equilibrium Constant

The effect of independent variables of Soxhlet extraction; temperature (35–55C), solvent-to-solid ratio (5–25, g/g) and particle size (0.15–0.6 mm) on oleoresin yield (% db), curcumin yield (% db) as well as total phenolic content (TPC) of extracts was investigated. Response surface methodology was used for optimization and the high correlation of the mathematical models indicated that a quadratic polynomial model could be used for optimization of the investigated responses. Multiresponse optimization study indicated that the optimum conditions for the extraction were extraction temperature 48.94C, solvent-to-solid ratio 20.95 and particle size 0.24 mm. The optimized conditions yielded 9.57% of oleoresin (db), 3.33% curcumin (db) and TPC 13.73 mg GAE/g. From the initial data of optimization, equilibrium studies were conducted considering the optimum particle size (0.24 mm) in a batch extractor at different temperatures ranging from room temperature (28C) to 50C. The equilibrium constant varied between 4.39 and 13.71 under these temperatures. Practical Application In this manuscript, response surface methodology approach has been used as an important research tool to evaluate the effect of different process variables on oleoresin extraction from turmeric. Also, an insight into equilibrium distribution relationship will help in equipment design and scaling up the extraction process.