Enhanced extraction of high added-value products from Hibiscus sabdariffa using automatic solvent extractor: Kinetics and modeling

Hibiscus sabdariffa was extracted by means of automatic solvent extraction, which is a perfect alternative in terms of Green Chemistry. Therefore, ethanol and water solution was selected as the solvent system when considering the principles (price, safety and convenience for health) of Green Chemistry. The process parameters of the extraction system was selected as ethanol concentration (10-80%), washing time for the extraction (40-60 min) and particle size of the solid Hibiscus sabdariffa sample (0.5-2 mm). Total polyphenols and anthocyanins were the response (measured) variables for the optimization of the automatic solvent extraction system by application of Face Centered Central Composite Design of Response Surface Method. The best findings for the total polyphenols and anthocyanins were 164.695 mg-GAE/g-dried plant and 28.349 mg-C3G/g-dried plant under the optimal conditions of the process (80% ethanol concentration, 60 min of washing time and 0.5 mm of particle size of the solid material). The most effective parameter was found as the solvent concentration followed by paticle size (P < 0.0001) for the recovery of total polyphenols, whereas the most significant process variable for the anthocyanins recovery was particle size, followed by ethanol concentration and washing time (P < 0.0001). Modeling of the kinetic data was performed by the second-order kinetic model and film theory. Effective diffusivities of total polyphenols and anthocyanins were calculated as 2.5 and 1.97 x 10(-10) m(2) s(-1) on the basis of kinetic evaluation. Additionally, the functional groups of the bioactive substances were also monitored by Fourier Transformed Infrared spectrometer